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Susitna‐Watana Hydroelectric Project Document
ARLIS Uniform Cover Page
Title:
Geomorphology study, Study plan Section 6.5, 2014-2015 Study
Implementation Report. [Main report] SuWa 289
Author(s) – Personal:
Author(s) – Corporate:
Tetra Tech
Watershed GeoDynamics
AEA‐identified category, if specified:
November 2015; Study Completion and 2014/2015 Implementation Reports
AEA‐identified series, if specified:
Series (ARLIS‐assigned report number):
Susitna-Watana Hydroelectric Project document number 289
Existing numbers on document:
Published by:
[Anchorage : Alaska Energy Authority, 2015]
Date published:
October 2015
Published for:
Alaska Energy Authority
Date or date range of report:
Volume and/or Part numbers:
Study plan Section 6.5
Final or Draft status, as indicated:
Document type:
Pagination:
vii, 101 pages (main report only)
Related work(s):
Appendix A and Attachment 1 (separate files)
Pages added/changed by ARLIS:
Notes:
Contents: 2014-2015 Study Implementation Report -- Appendix A. Susitna River upper river
reconnaissance photographs -- Attachment 1. Geomorphic reach delineation and characterization,
upper, middle and lower Susitna River segments - 2015 update technical memorandum.
The following parts of Section 6.5 appear in separate electronic files: Main report ; Appendix A ;
Attachment 1.
All reports in the Susitna‐Watana Hydroelectric Project Document series include an ARLIS‐
produced cover page and an ARLIS‐assigned number for uniformity and citability. All reports
are posted online at http://www.arlis.org/resources/susitna‐watana/
Susitna-Watana Hydroelectric Project
(FERC No. 14241)
Geomorphology Study
Study Plan Section 6.5
2014-2015 Study Implementation Report
Prepared for
Alaska Energy Authority
Prepared by
Tetra Tech
Watershed GeoDynamics
October 2015
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page i October 2015
TABLE OF CONTENTS
1. Introduction ....................................................................................................................... 1
2. Study Objectives................................................................................................................ 2
3. Study Area ......................................................................................................................... 4
4. Methods and Variances in 2014 ....................................................................................... 4
4.1. Study Component: Delineate Geomorphically Similar (Homogeneous)
Reaches and Characterize the Geomorphology of the Susitna River ................4
4.1.1. Variance from Study Plan ............................................................... 5
4.2. Study Component: Bed Load and Suspended-load Data Collection at Tsusena
Creek, Gold Creek, and Sunshine Gage Stations on the Susitna River,
Chulitna River near Talkeetna and the Talkeetna River near Talkeetna ...........6
4.2.1. Variance from Study Plan ............................................................... 6
4.3. Study Component: Sediment Supply and Transport Middle and Lower
Susitna River Segments .....................................................................................6
4.3.1. Variance from Study Plan ............................................................... 7
4.4. Study Component: Assess Geomorphic Change Middle and Lower Susitna
River Segments ..................................................................................................7
4.4.1. Variance from Study Plan ............................................................... 7
4.5. Study Component: Riverine Habitat versus Flow Relationship Middle Susitna
River Segment ....................................................................................................7
4.5.1. Variance from Study Plan ............................................................... 8
4.6. Study Component: Reconnaissance-Level Assessment of Project Effects on
Lower and Middle Susitna River Segments.......................................................9
4.6.1. Variances from Study Plan ............................................................. 9
4.7. Study Component: Riverine Habitat Area versus Flow Lower Susitna River
Segment............................................................................................................10
4.8. Study Component: Reservoir Geomorphology ................................................10
4.8.1. Variance from Study Plan ............................................................. 10
4.9. Study Component: Large Woody Debris .........................................................11
4.9.1. Variance from Study Plan ............................................................. 11
4.10. Study Component: Geomorphology of Stream Crossings along Transmission
Lines and Access Alignments ..........................................................................11
4.10.1. Variance from Study Plan ............................................................. 11
4.11. Study Component: Integration of Fluvial Geomorphology Modeling below
Watana Dam Study with the Geomorphology Study .......................................11
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FERC Project No. 14241 Page ii October 2015
4.11.1. Variance from Study Plan ............................................................. 12
5. Results .............................................................................................................................. 12
5.1. Study Component: Delineate Geomorphically Similar (Homogeneous)
Reaches and Characterize the Geomorphology of the Susitna River ..............13
5.1.1. Initial Geomorphic Reach Classification System ......................... 13
5.1.2. Initial Geomorphic Delineation .................................................... 14
5.1.3. Geomorphic Characterization of the Susitna River ...................... 14
5.2. Study Component: Bed Load and Suspended-load Data Collection at Tsusena
Creek, Gold Creek, and Sunshine Gage Stations on the Susitna River,
Chulitna River near Talkeetna and the Talkeetna River near Talkeetna .........16
5.3. Study Component: Sediment Supply and Transport Middle and Lower
Susitna River Segments ...................................................................................16
5.4. Study Component: Assess Geomorphic Change Middle and Lower Susitna
River Segments ................................................................................................17
5.5. Study Component: Riverine Habitat versus Flow Relationship Middle Susitna
River Segment ..................................................................................................17
5.6. Study Component: Reconnaissance-Level Assessment of Project Effects on
Lower and Middle Susitna River Segments.....................................................17
5.7. Study Component: Riverine Habitat Area versus Flow Lower Susitna River
Segment............................................................................................................18
5.8. Study Component: Reservoir Geomorphology ...............................................18
5.8.1. Reservoir Trap Efficiency and Sediment Accumulation Rates .... 18
5.8.2. Delta Formation ............................................................................ 18
5.8.3. Reservoir Erosion .......................................................................... 19
5.8.4. Bank and Boat Wave Erosion downstream of Watana Dam ........ 20
5.9. Study Component: Large Woody Debris .........................................................20
5.9.1. Aerial Photograph Inventory ......................................................... 20
5.9.2. Field Inventory .............................................................................. 20
5.10. Study Component: Geomorphology of Stream Crossings along Transmission
Lines and Access Alignments ..........................................................................20
5.11. Study Component: Integration of Fluvial Geomorphology Modeling below
Watana Dam Study with the Geomorphology Study .......................................21
6. Discussion......................................................................................................................... 21
6.1. Study Component: Delineate Geomorphically Similar (Homogeneous)
Reaches and Characterize the Geomorphology of the Susitna River ..............22
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FERC Project No. 14241 Page iii October 2015
6.2. Study Component: Bed- and Suspended-load Data Collection at Tsusena
Creek, Gold Creek, and Sunshine Gage Stations on the Susitna River,
Chulitna River near Talkeetna and the Talkeetna River near Talkeetna .........23
6.3. Study Component: Sediment Supply and Transport Middle and Lower Susitna
River Segments ................................................................................................24
6.4. Study Component: Assess Geomorphic Change Middle and Lower Susitna
River Segments ................................................................................................25
6.5. Study Component: Riverine Habitat versus Flow Relationship Middle Susitna
River Segment ..................................................................................................26
6.6. Study Component: Reconnaissance-Level Assessment of Project Effects on
Lower and Middle Susitna River Segments.....................................................28
6.7. Study Component: Riverine Habitat Area versus Flow Lower Susitna River
Segment............................................................................................................29
6.8. Study Component: Reservoir Geomorphology ................................................29
6.8.1. Reservoir Trap Efficiency and Sediment Accumulation Rates .... 29
6.8.2. Delta Formation ............................................................................ 30
6.8.3. Reservoir Erosion .......................................................................... 30
6.8.4. Bank and Boat Wave Erosion Downstream of Watana Dam ....... 31
6.9. Study Component: Large Woody Debris .........................................................31
6.10. Study Component: Geomorphology of Stream Crossings along Transmission
Lines and Access Alignments ..........................................................................32
6.11. Study Component: Integration of the Fluvial Geomorphology Modeling below
Watana Dam Study with the Geomorphology Study .......................................32
8. Literature Cited .............................................................................................................. 38
9. Tables ............................................................................................................................... 41
10. Figures .............................................................................................................................. 69
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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FERC Project No. 14241 Page iv October 2015
LIST OF TABLES
Table 5-1: Summary of cumulative data collected as part of the Geomorphology Study (Study
6.5) with URLs to access datasets, notes to find description of data in associated report, and
identification if data has previously been submitted and superseded. .......................................... 41
Table 5.1-1: Total Valley Bottom Area, Non-channel Valley Bottom Area, and Terrace Areas for
Middle River geomorphic reaches below Devils Canyon. ........................................................... 46
Table 5.1-2 Area and percentage of dissection and erosion of terrace units in Middle River
geomorphic reaches below Devils Canyon. .................................................................................. 47
Table 5.1-3 Opportunistic water quality parameters. .................................................................... 48
Table 5.1-4. Upstream and Downstream PRM Boundaries for Geomorphic Assessment Areas
Studied in 2013 and 2014. ............................................................................................................ 51
Table 5.2 -1. Dates and Locations of Sediment Transport Data collected by the USGS in 2014.
....................................................................................................................................................... 51
Table 5.2-2. Summary of Sediment Data Collected by USGS in 2012, 2013, and 2014. ........... 52
Table 5.2-3. USGS Suspended Sediment Transport Data Collected in 2012, 2013, and 2014. .. 54
Table 5.2-4. USGS Bed Load Sediment Transport Data Collected in 2012, 2013, and 2014. .... 58
Table 5.2-5. USGS Bed Material Data Collected in 2012, 2013, and 2014. ................................ 62
Table 5.8-1. Geomorphic notes of Upper River tributaries previously selected for study of
potential delta formation. .............................................................................................................. 63
Table 5.9-1. Large Woody Debris (LWD) Digitized from Aerial Photographs. .......................... 64
Table 5.10-1. Characteristics of stream crossings along the Denali East and portions of the
Denali West access routes. ............................................................................................................ 65
Table 5.11-1: Key used for Table 5.11-2. ..................................................................................... 67
Table 5.11-2: Initial framework for First-Order analysis of dam effects on river morphology. .. 67
Table 5.11-3: Initial framework for Second-Order dam effects analysis. .................................... 68
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LIST OF FIGURES
Figure 3-1: Susitna River geomorphology study area and large-scale river segments. ................ 70
Figure 5.1-1: Upper River Lateral Control and Sediment Source Mapping with illustrative photo
numbers noted (See Appendix A for photos) for Upstream Maclaren Confluence - PRM 291.8 to
PRM 278.9. ................................................................................................................................... 71
Figure 5.1-2: Upper River Lateral Control and Sediment Source Mapping with illustrative photo
numbers noted (See Appendix A for photos) for Upstream Maclaren River Confluence - PRM
278.9 to PRM 266.7 ...................................................................................................................... 72
Figure 5.1-3: Upper River Lateral Control and Sediment Source Mapping with illustrative photo
numbers noted (See Appendix A for photos) for Upstream Maclaren River Confluence – PRM
266.7 to PRM 261.3 ...................................................................................................................... 73
Figure 5.1-4: Upper River Lateral Control and Sediment Source Mapping with illustrative photo
numbers noted (See Appendix A for photos) for geomorphic reach UR-1. ................................. 74
Figure 5.1-5: Upper River Lateral Control and Sediment Source Mapping with illustrative photo
numbers noted (See Appendix A for photos) for geomorphic reach UR-2 .................................. 75
Figure 5.1-6: Upper River Lateral Control and Sediment Source Mapping with illustrative photo
numbers noted (See Appendix A for photos) for geomorphic reach UR-3. ................................. 76
Figure 5.1-7: Upper River Lateral Control and Sediment Source Mapping with illustrative photo
numbers noted (See Appendix A for photos) for geomorphic reach UR-4 .................................. 77
Figure 5.1-8: Upper River Lateral Control and Sediment Source Mapping with illustrative photo
numbers noted (See Appendix A for photos) for geomorphic reach UR-5 .................................. 78
Figure 5.1-9: Upper River Lateral Control and Sediment Source Mapping with illustrative photo
numbers noted (See Appendix A for photos) for geomorphic reach UR-6 .................................. 79
Figure 5.1-10: Cross-section UR 1.1 at PRM 257.9 (Q =- 17,400 cfs at Gold Creek gage). ....... 80
Figure 5.1-11: Cross-section UR 1.2 at PRM 253.4 (Q = 16,700 cfs at Gold Creek gage). ........ 81
Figure 5.1-12: Cross-section UR 2.1 at PRM 245.4 (Q = 17,000 cfs at Gold Creek gage). ........ 82
Figure 5.1-13: Cross-section UR 4.1 at PRM 220.7 (Q = 16,800 cfs at Gold Creek gage). ........ 83
Figure 5.8-1: View upstream Oshetna River from confluence with Susitna River. Clear water
evident. .......................................................................................................................................... 84
Figure 5.8-2. View upstream of Oshetna River fan at confluence with Susitna River. Helicopter
access present upstream and downstream of Oshetna River confluence on Susitna River left. ... 84
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Figure 5.8-3. View upstream Goose Creek from confluence with Susitna River. Plane-bed
channel evident. ............................................................................................................................ 85
Figure 5.8-4. View downstream Goose Creek to confluence with Susitna River ........................ 85
Figure 5.8-5. View upstream Jay creek above Jay Creek confluence with Susitna River. Log jams
present in channel. Channel filled-in with sand, gravel, boulder, and large wood deposits. ........ 86
Figure 5.8-6. Upstream Jay Creek fan, looking upstream Susitna River (right bank) along sheet
flow from Jay creek. Safe landing zones present upstream and downstream Jay Creek fan on
Susitna River right bank................................................................................................................ 86
Figure 5.8-7. View downstream Susitna River left bank to Kosina River fan. Plane-bed, boulder-
cobble channel evident. Safe landing zones present upstream and downstream Kosina River
confluence along Kosina fan. ........................................................................................................ 87
Figure 5.8-8. View downstream Watana Creek towards confluence with Susitna River. Gravel
deposits present along Watana Creek right bank. ......................................................................... 87
Figure 5.8-9. View upstream to Watana Creek (Susitna River right bank). Safe landing zones
present along Watana Creek fan and floodplain. .......................................................................... 88
Figure 5.8-10. View upstream Deadman Creek. Steep, confined, boulder-dominated channel
evident. .......................................................................................................................................... 88
Figure 5.8-11. View upstream Susitna River right bank upstream of Deadman Creek fan. Safe
landing zones present upstream and downstream of Deadman Creek confluence with Susitna
River. ............................................................................................................................................. 89
Figure 5.9-1. Large Woody Debris (LWD) by Species, 2013/2014 Field Inventory. ................. 90
Figure 5.9-2. Large Woody Debris (LWD) by Input Mechanism, 2013/2014 Field Inventory. . 91
Figure 5.9-3. Large Woody Debris (LWD) by Diameter, 2013/2014 Field Inventory. .............. 92
Figure 5.9-4. Large Woody Debris (LWD) by Freshness, 2014 Field Inventory. ....................... 93
Figure 5.9-5. Large Woody Debris (LWD) by Channel Position, 2014 Field Inventory. ........... 94
Figure 5.9-6. LWD Sample area PRM 9-12. ............................................................................... 95
Figure 5.9-7. LWD Sample area FA-151 Portage Creek. ............................................................ 96
Figure 5.9-8. LWD Sample area PRM 169.................................................................................. 97
Figure 5.9-9. LWD Sample area FA-173 Stephan Lake Complex. ............................................. 98
Figure 5.9-10. LWD Sample area PRM 181. ............................................................................... 99
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Figure 5.9-11. LWD Sample area FA-184 Watana Dam. .......................................................... 100
Figure 5.10-1. Map of access corridor reconnaissance route and stream crossings identified
during reconnaissance. ................................................................................................................ 101
APPENDICES AND ATTACHMENTS
Appendix A: Susitna River Upper River Reconnaissance Photographs
Attachment 1:Geomorphic Reach Delineation and Characterization, Upper, Middle and Lower
Susitna River Segments – 2015 Update Technical Memorandum
:
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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FERC Project No. 14241 Page 1 October 2015
1. INTRODUCTION
The Geomorphology Study, Section 6.5 of the Revised Study Plan (RSP) approved by the
Federal Energy Regulatory Commission (FERC) for the Susitna-Watana Hydroelectric Project,
FERC Project No. 14241, focuses on characterization of the geomorphology of the Susitna
River, and to evaluate the effects of the Project on the geomorphology and dynamics of the river
by predicting the trend and magnitude of geomorphic response.
A summary of the development of this study, together with the Alaska Energy Authority’s
(AEA) implementation of it through the 2013 study season, appears in Part A, Section 1 of the
Initial Study Report (ISR) filed with FERC in June 2014. As required under FERC’s regulations
for the Integrated Licensing Process (ILP), the ISR describes AEA’s “overall progress in
implementing the study plan and schedule and the data collected, including an explanation of any
variance from the study plan and schedule.” (18 CFR 5.15(c)(1)).
Since filing the ISR in June 2014, AEA has continued to implement the FERC-approved plan for
the Geomorphology Study, Section 6.5. For example:
Characterization of the geomorphology of the Upper River Segment and on upstream to
the Denali Highway Bridge (RSP Section 6.5.4.1.2.3 and ISR Section 7.2.1.1.3) based on
the Upper River Reconnaissance
Collection of 2014 bed and suspended-load sediment transport data by the USGS (RSP
Section 6.5.4.2 and ISR Section 7.2.1.2)
Aerial reconnaissance of the reservoir area tributaries (RSP Section 6.5.4.8.2.2 and ISR
Section 7.2.1.8)
Completion of large woody debris (LWD) sampling in the Middle and Lower Rivers
(RSP Section 6.5.4.9 and ISR Section 7.2.1.9)
AEA held the first ISR meeting for Studies 6.5 and 6.6 in October 15-17, 21-23, 2014 in
Anchorage
AEA has completed the following technical memorandum:
o Susitna River Historical Cross Section Comparison (Tetra Tech 2014a)
o Update of Sediment Transport Relationships and a Revised Sediment Balance for
the Middle and Lower Susitna River Segments (Tetra Tech 2014b)
o Mapping of Geomorphic Features and Turnover within the Middle and Lower
Susitna River Segments from 1950s, 1980s, and Current Aerials (Tetra Tech
2014c)
o Updated Mapping of Aquatic Macrohabitat Types in the Middle Susitna River
Segment from 1980s and Current Aerials (Tetra Tech 2014d)
o Assessment of the Potential for Changes in Sediment Delivery to Watana
Reservoir Due to Glacial Surges (Tetra Tech 2014e)
o Dam Effects on Downstream Channel and Floodplain Geomorphology and
Riparian Plant Communities and Ecosystems – A Critical Literature Review (R2
Resource Consultants, Inc. and Tetra Tech 2014)
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o Geomorphic Reach Delineation and Characterization, Upper, Middle and Lower
Susitna River Segments – 2015 Update (Tetra Tech 2015a). (AEA notes that the
geomorphic reach delineation technical memorandum was updated in 2015 to
reflect the more detailed information gathered during the August 2014 field
reconnaissance of the Upper River Segment and bed material samples collected in
the 2014 winter and summer field seasons. The updated version of this technical
memorandum Attachment 1 to this report.)
In furtherance of the next round of ISR meetings and FERC’s SPD expected in 2016, this report
describes AEA’s overall progress in implementing the Geomorphology Study, Study 6.5, during
calendar year 2014. Rather than a comprehensive reporting of all field work, data collection, and
data analysis since the beginning of AEA’s study program, this report is intended to supplement
and update the information presented in Part A of the ISR for the Geomorphology Study, Study
6.5, through the end of calendar year 2014. It describes the methods and results of the 2014
effort, and includes a discussion of the results achieved.
2. STUDY OBJECTIVES
The overall goal of the Geomorphology Study is to characterize the geomorphology of the
Susitna River, and to evaluate the effects of the Project on the geomorphology and dynamics of
the river by predicting the trend and magnitude of geomorphic response. This will inform the
analysis of potential Project-induced impacts to aquatic and riparian habitats. The results of this
study, along with results of the Fluvial Geomorphology Modeling below Watana Dam Study
(Study 6.6), will be used in combination with geomorphic principles and criteria/thresholds
defining probable channel forms to predict the potential for alteration of channel morphology
from Project operation. This information will be used to assist in determining whether
protection, mitigation, or enhancement measures may be needed, and if so, what those measures
may be. More specific goals of the Geomorphology Study are as follows:
Determine how the river system functions under existing conditions.
Determine how the current system forms and maintains a range of aquatic and channel
margin habitats.
Identify the magnitudes of changes in the controlling variables and how these will affect
existing channel morphology in the identified reaches downstream of the dam and in the
areas upstream of the dam affected by the reservoir.
In an integrated effort with the Fluvial Geomorphology Modeling below Watana Dam
Study (Study 6.6), determine the likely changes to existing habitats through time and
space.
In order to achieve the study goals, there are 11 study objectives:
1. Geomorphically characterize the Project-affected river channels and floodplain including:
Delineate the Susitna River into geomorphically similar reaches.
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Characterize and map relic geomorphic forms from past glaciation and debris flow
events.
Characterize and map the geology of the Susitna River, identifying controlling features of
channel and floodplain geomorphology.
Identify and describe the primary geomorphic processes that create, influence, and
maintain mapped geomorphic features.
2. Collect sediment transport data to supplement historical data to support the characterization
of Susitna River sediment supply and transport.
3. Determine sediment supply and transport in Middle and Lower Susitna River Segments.
4. Assess geomorphic stability/change in the Middle and Lower Susitna River Segments.
5. Characterize the surface area versus flow relationships for riverine macrohabitat types (1980s
main channel, side channel, side sloughs, upland sloughs, tributaries and tributary mouths)
over a range of flows in the Middle Susitna River Segment.
6. Conduct a reconnaissance-level geomorphic assessment of potential Project effects on the
Lower and Middle Susitna River Segments considering Project-related changes to stream
flow and sediment supply and a conceptual framework for geomorphic reach response.
7. Conduct a phased characterization of the surface area versus flow relationships for riverine
macrohabitat types in the Lower Susitna River Segment including:
Delineation of aquatic macrohabitat per 1980s definitions for selected sites.
Comparison of 1980s versus existing macrohabitat areas at selected sites.
Estimate potential change in macrohabitat areas based on initial estimates of change in
stage from Project operations.
Optional – If Focus Areas are extended into the Lower Susitna River Segment, perform
analysis of macrohabitat wetted area versus flow relationships for additional sites and
flows.
8. Characterize the proposed Watana Reservoir geomorphology and changes resulting from
conversion of the channel/valley to a reservoir.
9. Assess large woody debris transport and recruitment, their influence on geomorphic forms
and, in conjunction with the Fluvial Geomorphology Modeling below Watana Dam Study,
effects related to the Project.
10. Characterize geomorphic conditions at stream crossings along access road/transmission line
alignments.
11. Integration with the Fluvial Geomorphology Modeling below Watana Dam Study to develop
estimates of Project effects on the creation and maintenance of the geomorphic features that
comprise important aquatic and riparian macrohabitats and other key habitat indicators, with
particular focus on side channels, side sloughs, and upland sloughs.
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3. STUDY AREA
The study area for the Geomorphology Study is the Susitna River from its confluence with the
Maclaren River (PRM 261.3[RM 260]) downstream to the mouth at Cook Inlet (PRM 3.3[RM
0]). The study area has been divided into three large-scale river segments:
Upper Susitna River Segment: Maclaren River confluence (PRM 261.3[RM 260])
downstream to the proposed Watana Dam site (PRM 187.1 [RM 184]).
Middle Susitna River Segment: Proposed Watana Dam site (PRM 187.1 [RM 184])
downstream to the Three Rivers Confluence (PRM 102.4 [RM 98]).
Lower Susitna River Segment: Three Rivers Confluence (PRM 102.4 [RM 98])
downstream to Cook Inlet (PRM 3.3 [RM 0]).
Each of the 11 study components that make up the Geomorphology Study has a component-
specific study area often related to the three large-scale river segments identified above. The
study area and river segments are shown on Figure 3-1. Identification of the study area that each
study component addresses is provided in the discussion of each study component in RSP
Section 6.5.4, Study Methods.
4. METHODS AND VARIANCES IN 2014
The implementation of the 11 Geomorphology Study components and variances in 2014 are
presented in this section. The variances listed in this section are continuations of 2013 variances
described in the ISR Part A and proposed as study plan modifications in ISR Part C Section
7.1.2. No new variances were identified in 2014.
4.1. Study Component: Delineate Geomorphically Similar
(Homogeneous) Reaches and Characterize the Geomorphology
of the Susitna River
This study component has been carried out in accordance with ISR Study 6.5 Section 4.1 and
RSP Section 6.5.4.1. It consists of three tasks: Identification and Development of Geomorphic
Classification System (RSP Section 6.5.4.1.2.1), Geomorphic Reach Delineation (RSP Section
6.5.4.1.2.2), and Geomorphic Characterization of the Susitna River (RSP Section 6.5.4.1.2.3).
2014 activities for this study component were performed under two of the three tasks. For the
Identification and Development of Geomorphic Classification System task, no work was
performed in 2014. As identified in ISR Study 6.5 Section 7.2.1.1.1, this task has been completed
and is reported in two technical memoranda (TM). This includes the May 2014 filing of the
technical memorandum Geomorphic Reach Delineation and Characterization, Upper, Middle
and Lower Susitna River Segments (Tetra Tech 2014f) which was an update to the 2012 Study
Technical Memorandum, Initial Geomorphic Reach Delineation and Characterization, Middle
and Lower Susitna River Segments (Tetra Tech 2013a).
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For the second task, the Geomorphic Reach Delineation task (ISR Study 6.5 Section 7.2.1.1.2)
the 2014 bed material samples collected in Study 6.6 were used to update the bed material sizes
representing each reach and the cross section survey data were used to update the representative
channel slopes for several reaches. Characterization of the Upper Susitna River Segment was
refined based on results of the Upper River Geomorphic Reach reconnaissance conducted in
August 2014. These efforts resulted in the revised technical memorandum Geomorphic Reach
Delineation and Characterization, Upper, Middle and Lower Susitna River Segments – 2015
Update provided in Attachment 1.
Activities in 2014 for the third task, the Geomorphic Characterization of the Susitna River (ISR
Study 6.5 Section 7.2.1.1.3), include:
(1) Correlation of geomorphic surfaces with water-surface elevations determined from
hydraulics generated by the 1-D and/or 2-D Bed Evolution models (Study 6.6);
(2) Integration of ice-modeling efforts (ice jam backwater and/or dam break surge) with
geomorphic surfaces and system dynamics (Study 7.6);
(3) Further investigation of 7 extended Geomorphic Assessment Areas (GAAs) to ground-
truth aerial/LiDAR based mapping;
(4) Integration of data from riparian investigations (Study 8.6) including vegetation mapping
and aging to better define age constraints in FAs;
(5) Analysis of the spatial distribution of geomorphic surfaces and channel types within
different aged components of the FAs;
(6) Integration of turnover analysis results with FA dynamics;
(7) Additional geomorphic characterization of the Upper and Lower Susitna River Segments;
(8) Development of similar level geomorphic characterization of the Upper River reaches;
and
(9) Investigation of sources of sand that is the volumetrically significant fraction of the
sediment load for construction of geomorphic surfaces in the Middle River.
During the Upper River reconnaissance opportunistic water quality parameters were collected.
This included water depth, water temperature, conductivity, turbidity, and reduction potential
(ORP). The parameters were sampled with a YSI 556MPS water quality meter and MicroTPW
turbidity meter. This activity was not part of the FERC-approved Study Plan.
In addition to these characterization efforts, the technical memorandum Susitna River Historical
Cross Section Comparison (Tetra Tech. 2014a) was filed on September 17, 2014. This technical
memorandum provides a comparison of cross sections that were surveyed in the 1980s with
those surveyed in 2012 and 2013. This information has been used by the Fluvial Geomorphology
Modeling Study (6.6) to help in the validation of the 1-D bed evolution model in the Middle
Susitna River segment. This effort was part of the third task of this study component.
4.1.1. Variance from Study Plan
There was one variance in 2014 to the Study Plan for this study component. This involved the
collection of opportunistic water quality samples while performing the Upper River
reconnaissance. This variance will enhance AEA’s ability to meet objectives of the Water
Quality Baseline Study (5.5) and Fish Distribution and Abundance in the Upper Susitna River
(9.5) by providing additional water quality data.
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4.2. Study Component: Bed Load and Suspended-load Data
Collection at Tsusena Creek, Gold Creek, and Sunshine Gage
Stations on the Susitna River, Chulitna River near Talkeetna
and the Talkeetna River near Talkeetna
In accordance with RSP 6.5.4.2, this study component consists of data collection by the USGS to
characterize sediment transport conditions in the Susitna River and its major tributaries within
the Study Area. In 2014, USGS continued data collection at all of the 2013 sites. This effort was
performed per methods described in ISR Study 6.5 Section 4.2. This study component is
complete.
4.2.1. Variance from Study Plan
As described in ISR Part A Section 4.2.3, collection of bedload samples from the Tsusena Creek
gage site were terminated after 2012 due to logistical and safety concerns. This variance was
proposed as a modification to the study (ISR Part C Section 7.1.2.2) and was implemented in
2014 as a variance to the Study Plan. This variance did not affect AEA’s ability to meet the
objectives of this study component.
4.3. Study Component: Sediment Supply and Transport Middle and
Lower Susitna River Segments
This study component (RSP Section 6.5.4.3) consists of several tasks to characterize the
sediment supply and transport conditions in the Susitna River between the Watana Dam site
(PRM 187.1) and Susitna Station (PRM 29.9). This effort provided the sediment input from the
mainstem and major Susitna River tributaries for the bed evolution modeling efforts performed
in the Fluvial Geomorphology Modeling Study (RSP Section 6.6). Tasks include Middle and
Lower Susitna River sediment balance (RSP Sections 6.5.4.3.2.1 and 6.5.4.3.2.2),
characterization of bed material mobilization (RSP Section 6.5.4.3.2.3), and determination of
effective discharge (RSP Section 6.5.4.3.2.4).
The 2014 activities for this study component included performing a more detailed pre-Project
sediment balance for the Middle Susitna River Segment than presented in an earlier technical
memorandum (Tetra Tech 2013a). This activity was performed with methods identified in ISR
Part A Section 4.3 and further discussed in the technical memorandum filed September 17, 2014
(Tetra Tech 2014b).
Although not identified in the Study Plan, the availability of helicopter flight time provide d the
opportunity for the Geomorphology Study (6.5) to collect video of the Susitna River to support
identification of mass wasting and sediment supply within the channel for both the Middle and
Lower Susitna River segments. The videos are a mechanism to characterize tributaries and their
contributing watersheds in terms of bed rock controls, lateral sediment sources, and potential
sediment sinks. This data will support a more detailed pre-Project sediment balance for the
Middle and Lower Susitna River segments.
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4.3.1. Variance from Study Plan
Two variances in the methods related to sediment transport calculations were continued in 2014.
These were also described as variances in 2013 (Study 6.5 ISR Part A Section 4.3.3) and were
proposed as modifications to the Study Plan (see Study 6.5 ISR Part C Section 7.1.2.3). One
variance involved the time period for calculating total sediment load and the resulting sediment
balance and the other involved a calculation procedure for effective discharge. These variances,
as described in ISR Part C Section 7.1.2.3, were implemented in 2014. The entire available flow
record (61 years) was used to evaluate sediment loads rather than only representative dry,
average and wet years and equal arithmetic bins were used to evaluate effective discharge rather
than logarithmic bins. These variances did not affect AEA’s ability to meet the objectives of this
study component.
A third variance involved collecting videos during reconnaissance trips on the Middle and Lower
Susitna River. These videos help document conditions of tributaries and potential sources of
sediment from mass wasting along the mainstem Susitna River. These opportunistically collected
videos from aerial reconnaissance enhance AEA’s ability to meet the objectives of this study
component.
4.4. Study Component: Assess Geomorphic Change Middle and
Lower Susitna River Segments
This study component compared existing, 1980s, and 1950s geomorphic feature data mapped
from analysis of aerial photography to characterize channel stability and change and the
distribution of geomorphic features under unregulated flow conditions (RSP Section 6.5.4.4).
The 2014 activities for this study component included completing the mapping of geomorphic
features in the Middle and Lower River segments from 1950s photography, assessing channel
change between 2012 and 2013 aerial photography, completing the turnover analysis in the
Middle and Lower River segments and revising the previously developed technical
memorandum (Tetra Tech 2013g) (ISR Study 6.5, Part C, Section 7.2.1.4). The results are
presented in September 26, 2014 filed technical memorandum Mapping of Geomorphic Features
and Turnover within the Middle and Lower Susitna River Segments from 1950s, 1980s, and
Current Aerials (Tetra Tech 2014c). These activities were performed with methods identified in
ISR Study 6.5 Section 4.4 and are presented in further detail in the 2014 developed technical
memorandum (Tetra Tech 2014c). This study component has been completed.
4.4.1. Variance from Study Plan
There were no variances in 2014 to the Study Plan for this study component.
4.5. Study Component: Riverine Habitat versus Flow Relationship
Middle Susitna River Segment
This study component delineated current and 1980s riverine macrohabitat types and developed
wetted habitat area data over a range of flows. The effort is broken into three tasks: acquisition
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and processing of aerial photography, digitization of riverine macrohabitat types and riverine
macrohabitat analysis (RSP Section 6.5.4.5).
The 2014 activities for this study component included expanding the mapping of aquatic
macrohabitat types to 100 percent of the Middle River Segment, coordinating with Study 9.9 and
Study 8.5 to ensure consistent mapping, and updating the aquatic macrohabitat technical
memorandum (Tetra Tech 2013f) (ISR Study 6.5, Part C, Section 7.2.1.5). The results are
presented in September 26, 2014 Updated Mapping of Aquatic Macrohabitat Types in the Middle
Susitna River Segment from 1980s and Current Aerials (Tetra Tech 2014d). These activities
were performed with methods identified in ISR Study 6.5, Part A, Section 4.5 and further
discussed in the 2014 developed technical memorandum (Tetra Tech 2014d). This study
component has been completed.
4.5.1. Variance from Study Plan
There is one variance identified for this study component that was also described as a variance in
ISR Study 6.5, Part A, Section 4.5.3 and was proposed as a modification in ISR Study 6.5, Part
C, Section 7.1.2.5. It involves the collection of aerial photography in the Middle and Lower
Susitna River Segments. In 2012 and again in 2013, aerial photography was acquired at a single
target flow rather than the three flows identified in the RSP (Section 6.5.4.5.2.1). The Study Plan
identified acquisition of three sets of aerial photography in 2012 approximately corresponding to
the following discharges: 23,000, 12,500, and 5,100 cfs. The actual aerial photography coverage
of the Middle River obtained in 2012 was comprised of 50 percent at 12,900 cfs (PRM 143.6 to
PRM 102.4) and 50 percent at 17,000 cfs (PRM 187.1 to PRM 143.6). In 2013, it was decided to
acquire additional aerial photographs for only the 12,500-cfs target discharge in the Middle
River. Aerials were obtained for about 60 percent of the Middle River at 11,300 cfs and
40 percent at 6,200 cfs.
One goal of acquiring three sets of 2012 aerials was to compare the macrohabitat versus flow
relationships from current conditions to 1980s information and determine if there is a difference
in the habitat areas for current conditions from those mapped in the 1980s at similar flows. This
goal was met by collection of the single set of aerial photography in 2012. Using the 2012 aerial
photography, AEA concluded that the macrohabitat areas were appreciably different from those
mapped in the 1980s (Tetra Tech 2013f). Subsequently, AEA also concluded that aerial
photography collected at multiple specified discharges to develop macrohabitat versus flow
relationships was not necessary for meeting the overall objectives of the Study Plan as the
combination of the 2-D hydraulic modeling, bathymetry and topography collected in the Focus
Areas will provide direct determination of the area of the various macrohabitat types over the
range of flows of interest. Therefore, development of macrohabitat area versus flow relationships
from aerial photographs collected at specified discharges as identified as a goal of this study
component are not needed. This variance and the alternative approach were presented at both the
September 25, 2013 and December 2, 2013 Technical Work Group meetings. The objectives of
the study will be met without collecting additional aerials at three flows as specified in the RSP
(Section 6.5.4.5.2.1).
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4.6. Study Component: Reconnaissance-Level Assessment of
Project Effects on Lower and Middle Susitna River Segments
This study component utilizes comparison of pre- and Post-Project flows and sediment transport
conditions to estimate the potential for post-Project channel change in the Lower and Middle
Susitna River segments. Specific tasks under this study component included a stream flow
assessment (RSP 6.5.4.6.2.1), a sediment transport assessment (RSP Section 6.5.4.6.2.2), the
identification of geomorphic reach response through the integration of the stream flow and
sediment transport assessments (RSP Section 6.5.4.6.2.3), and a literature review of downstream
effects of dams (RSP Section 6.5.4.6.2.4).
The primary 2014 activities for this study component included refining the sediment transport
assessment results for the pre-Project scenarios and completion of a technical memorandum on
the downstream effects of dams in conjunction with Study 8.6 (ISR Study 6.5, Part C, Section
7.2.1.6). These activities were performed with methods identified in ISR Study 6.5, Part A,
Section 4.6.2.2 and 4.6.2.4, respectively. The results of these activities are presented in Dam
Effects on Downstream Channel and Floodplain Geomorphology and Riparian Plant
Communities and Ecosystems – A Critical Literature Review (R2 and Tetra Tech 2014) filed
November 14, 2014 and Update of Sediment-Transport Relationships and a Revised Sediment
Balance for the Middle and Lower Susitna River Segments (Tetra Tech 2014b) filed September
17, 2014.
In support of the decision as to whether to continue the 1-D bed evolution model downstream of
PRM 29.9, Project related changes in the magnitude of peak flows at Sunshine and Susitna
station and changes in flow duration at Susitna Station were determined based on comparison of
pre-Project and Max LF OS-1b flows. This effort is a continuation of the streamflow assessment
identified in Study 6.5 ISR, Part A, Section 4.6.2.1. The annual peak flows to perform the
frequency analysis and the daily flows to perform the flow duration analysis for the Max LF OS-
1b condition were developed using the routed flows from the 1-D bed evolution model as
described in Section 4.2.3 of the technical memorandum Decision Point on Fluvial
Geomorphology Modeling of the Susitna River below PRM 29.9 (Tetra Tech 2014g) filed
September 26, 2014. The methods for developing the peak flow and flow duration analyses are
presented in Section 4.3.1 of Tetra Tech (2014g).
4.6.1. Variances from Study Plan
In the RSP Section 6.5.4.6.2.1 and the ISR Study 6.5, Part A, Section 4.6.3, it was indicated that
hydrologic analysis of operational scenarios beyond the initial streamflow assessment would be
performed in the Fish and Aquatics IFS (Study 8.5). However, in 2014 in support of the decision
on whether to extend the 1-D bed evolution model downstream of PRM 29.9, hydrologic
analyses of Max LF OS-1b were performed in the Geomorphology Study (6.5). The analysis is
documented in Tetra Tech (2014g). Therefore in 2014, there was not a variance related to
performance of hydrologic analysis by the Geomorphology Study (6.5).
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4.7. Study Component: Riverine Habitat Area versus Flow Lower
Susitna River Segment
This study component consists of an initial assessment of the potential for Project effects
associated with changes in stage to alter Lower Susitna River Segment riverine habitat (RSP
Section 6.5.4.7). This study component was completed in 2013 and the methods and results are
summarized in the ISR 6.5 Section 4.7 and Section 5.7., respectively. The detailed results were
presented in three technical memoranda filed in February and March 2013 titled Stream Flow
Assessment. Susitna-Watana Hydroelectric Project (Tetra Tech 2013d), Synthesis of 1980s
Aquatic Habitat Information (Tetra Tech 2013e), and Mapping of Aquatic Macrohabitat Types at
Selected Sites in the Middle and Lower Susitna River Segments from 1980s and 2012 Aerials
(Tetra Tech 2013f). As described in ISR Section 4.7.3, there were no variances to the Study Plan.
4.8. Study Component: Reservoir Geomorphology
This study component consists of characterizing geomorphic changes resulting from conversion
of the channel and portions of the river valley to a reservoir. Specific tasks under this study
component include: estimation of reservoir trap efficiency and sediment accumulation rates (RSP
Section 6.5.4.8.2.1), estimation of the formation of tributary deltas in the reservoir fluctuation
zone (RSP Section 6.5.4.8.2.2), assessment of reservoir erosion (RSP Section 6.5.4.8.2.3), and
bank and boat wave erosion downstream of Watana Dam (RSP Section 6.5.4.8.2.4).
The 2014 activities for this study component involve three of the four study tasks (ISR Study 6.5,
Part C, Section 7.2.1.8). The first set of activities fell under the Reservoir Trap Efficiency and
Sediment Accumulation task and included coordinating with the Water Quality Modeling Study
(Study 5.6) and the sediment transport aspects of the reservoir modeling and supplying trap
efficiency estimates to the Fluvial Geomorphology Modeling Study (Study 6.6). The sediment
trap efficiency estimates were used in Study 6.6 to modify the sediment supply to the Middle
River Segment for modeling of the with-Project conditions.
In addition, an analysis of the potential changes to sediment delivery from the upper Susitna
watershed into the reservoir from glacial surges was performed. This effort was added as a result
of the February 1, 2013 FERC SPD. The methods to conduct this effort are documented in the
technical memorandum Assessment of the Potential for Changes in Sediment Delivery to Watana
Reservoir Due to Glacial Surges filed November 14, 2014 (Tetra Tech. 2014e).
Under the Delta Formation task an aerial reconnaissance of selected tributaries for potential delta
formation was performed. The purpose of this effort was to assist in developing plans for field
data collection efforts.
For the third task, Reservoir Erosion, the 2014 activities consisted of performing coordination
with the Geology and Soils Characterization Study (Study 4.5). These activities were performed
with methods identified in ISR Study 6.5, Part A, Section 4.8.
4.8.1. Variance from Study Plan
There were no variances in 2014 to the Study Plan for this study component.
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4.9. Study Component: Large Woody Debris
This study component, as identified in RSP Section 6.5.4.9, assesses the potential for Project
construction and operation to affect the input, transport, and storage of large woody debris
(LWD) in the Susitna River. Data development efforts to support the assessment of Project
effects include inventory of LWD from aerial photography and inventory of LWD from field
surveys.
The 2014 activities for this study component include digitizing large woody debris from 2012,
2013, and 1983 aerial photography in the Lower, Middle, and Upper river segments, and
completing a field inventory of LWD within the remaining LWD sample areas downstream of
PRM 187.1 (ISR Study 6.5, Part C, Section 7.2.1.9). These activities were performed with
methods identified in ISR Study 6.5 Section 4.9.
4.9.1. Variance from Study Plan
There were no variances to the Study Plan related to the work carried out in 2014 for this study
component.
4.10. Study Component: Geomorphology of Stream Crossings along
Transmission Lines and Access Alignments
This study component as identified in RSP Section 6.5.4.10 consists of characterizing the
existing geomorphic conditions at stream crossings along access road/transmission line
alignments and to determine potential geomorphic changes resulting from construction,
operation, and maintenance of the roads and stream crossing structures.
The 2014 activities for this study component include an aerial field reconnaissance to identify
conditions along the corridors and refinement of remaining field data collection (ISR Study 6.5,
Part C, Section 7.2.1.10).
4.10.1. Variance from Study Plan
No variances from the Study Plan occurred in 2014.
4.11. Study Component: Integration of Fluvial Geomorphology
Modeling below Watana Dam Study with the Geomorphology
Study
This study component as identified in RSP Section 6.5.4.11 consists of two-way integration
between the Geomorphology Study and the Fluvial Geomorphology Modeling Study (Study 6.6).
The efforts of the Geomorphology Study identify the specific geomorphic (and habitat-related)
processes that require further quantification, identify a significant portion of the data needs, and
provides the basic information and context for performing the Fluvial Geomorphology Modeling
Study. The Geomorphology Study (6.5) will apply its results to help guide the development and
application of the various modeling efforts. After completion of the modeling, the study team
will use the results from both studies in an integrated manner to provide interpretations with
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respect to the issues that must be addressed, including predictions of potential changes to key
geomorphic features that comprise the aquatic and riparian habitat.
The 2014 activities for this study component included reviewing the initial pre-Project and post-
Project 1-D model run in the Middle and Lower Susitna River segments, interpreting results in
terms of geomorphic response, and refining conceptual models describing the system, where
necessary (ISR Study 6.5, Part C, Section 7.2.1.11). These activities were performed with
methods identified in ISR Study 6.5 Section 4.11.
To support study component objectives, an initial framework for integration of the studies was
developed based on the First- and Second-order impacts components of the four-order
hierarchical evaluation of dam-related impacts identified in the Technical Memorandum - Dam
Effects on Downstream Channel and Floodplain Geomorphology and Riparian Plant
Communities and Ecosystems – A critical Literature Review (Figure 1) (R2 Resource
Consultants and Tetra Tech 2014). First-order impacts are changes to the primary physical
drivers of the fluvial system: hydrology, sediment supply and ice processes. Second-order
impacts result from changes in hydrology, sediment transport, ice process dynamics and channel
and floodplain morphology. Third-order impacts are the ecological responses to the altered
physical habitat and Fourth-order impacts describe biogeomorphic feedback between ecological
responses and physical processes.
4.11.1. Variance from Study Plan
There were no variances to the Study Plan related to the work carried out in 2014 for this study
component.
5. RESULTS
In 2014, activities for 10 of the 11 study components of the Geomorphology Study (6.5) were
performed and associated results are reported in this section. In many cases, the results are
reported in technical memoranda filed in 2014. In these cases, reference is made to the technical
memoranda presenting the results. A list of all data filed in association with the performance of
the Geomorphology Study (6.5) is provided in Table 5-1. This table is cumulative and includes
data from 2012, 2013 and 2014. Each of the 9 columns of Table 5-1 are described below. The
table is broken into two primary columns: (1) Active Data, and (2) Previously Submitted Data
(now superseded). Each of these primary columns has sub-columns that further describe the data.
To describe Table 5-1 below, the column headings are bolded and underlined, while the
description of the contents of each column follow after the colon.
Column heading: description of contents
Active Data
Data: Title of data delivered
Data Type: The type of data delivered (i.e. ArcGIS Shapefile, JPEG, Excel Spreadsheet,
MP4 Videos, LRV files, AVCHD Videos, PDF, GeoTIFF or MrSID)
File name: Submitted name of data file.
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Location (URLs in footnotes): Alphabetical letter noted. Each letter corresponds to a
URL of where to find the data. Locations of the data may be found at the following:
a: http://gis.suhydro.org/isr/06-Geomorphology/6.5-Geomorphology/
b: http://gis.suhydro.org/Post_ISR/06-Geomorphology/6.5-Geomorphology/
c: http://gis.suhydro.org/raster-data
d: http://gis.suhydro.org/SIR/06-Geomorphology/6.5-Geomorphology/
e:http://gis.suhydro.org/SIR/06-Geomorphology/6.6-
Fluvial_Geomorphology_Modeling/
f: http://pubs.usgs.gov/sir/2012/5210/
Folder Nesting: The folder nesting sequence to locate the specified data at the
corresponding URL.
Study 6.5 Study Component: Study component number associated with Study 6.5. The
study component number corresponds to the number identified in the first decimal
position of the RSP, ISR, or SIR section number (i.e. Section X.Y) where X identifies the
section number (i.e. methods, results, or discussion) and Y identifies the study component
associated with Study 6.5.
Data described in following report: Report where data is discussed. Using the indicated
report, and study component number (where applicable), one can identify where in the
specified report, data is further discussed.
Previously submitted Data (now superseded):
File Name: Submitted name of data file
Location: Alphabetical letter associated with URLs listed in footnotes.
In 2014 three of the Geomorphology Study (6.5) study components were completed. These study
components were Bed Load and Suspended-load Data Collection at Tsusena Creek, Gold Creek,
and Sunshine Gage Stations on the Susitna River, Chulitna River near Talkeetna and the
Talkeetna River near Talkeetna (RSP Section 6.5.4.2), Assess Geomorphic Change Middle and
Lower Susitna River Segments (RSP Section 6.5.4.4) and Riverine Habitat versus Flow
Relationship Middle Susitna River Segment (RSP Section 6.5.4.5).
No activities were performed in 2014 on the Riverine Habitat Area versus Flow Lower Susitna
River Segment (RSP Section 6.5.4.7) study component as it was completed in 2013.
5.1. Study Component: Delineate Geomorphically Similar
(Homogeneous) Reaches and Characterize the Geomorphology
of the Susitna River
5.1.1. Initial Geomorphic Reach Classification System
No work was performed in 2014 for this task. As identified in ISR Study 6.5 Section 7.2.1.1.1,
this task has been completed and reported on in two technical memoranda memorandums (TM).
This includes the May 2014 filing of the technical memorandum Geomorphic Reach Delineation
and Characterization, Upper, Middle and Lower Susitna River Segments (Tetra Tech 2014a)
which was an update to the 2012 Study Technical Memorandum, Initial Geomorphic Reach
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Delineation and Characterization, Middle and Lower Susitna River Segments (Tetra Tech
2013a).
5.1.2. Initial Geomorphic Delineation
As identified in Study 6.5 ISR Section 7.2.1.1.2, bed-material data in the Upper, Middle, and
Lower Susitna River segments as part of Study 6.6 was collected during the 2014 study season
and was used to update morphometric parameters in the geomorphic reaches. The updated data
are presented in Table 5.2-2 of the technical memorandum presented in Attachment 1 titled
Geomorphic Reach Delineation and Characterization, Upper, Middle and Lower Susitna River
Segments – 2015 Update. Further, thalweg profile data in the Middle and Lower Susitna River
segments as part of Study 8.5 were collected during the 2014 study season and used to update the
profiles in the Middle and Lower Susitna River segments in Figure 5.1-1, Figure 5.4-2, and
Figure 5.5-2 of Attachment 1.
5.1.3. Geomorphic Characterization of the Susitna River
Further investigation of the geomorphic surfaces in the 7 Geomorphic Assessment Areas studied
in 2013 to ground-truth aerials and LiDAR-based mapping (Section 4.1 Activity 3) and
integration of turnover analysis results with FA dynamics (Section 4.1 Activity 6) has initiated
an analysis of geomorphic surface heights and flow overtopping frequencies (Section 4.1
Activity 1). The analysis involved comparing geomorphic surface heights derived from 2014
LiDAR to the 100-year water surface elevations from the 1-D Hydraulic Model developed in
Study 6.6. Surfaces above the 100-year water surface elevation, by definition, are defined as
terraces. These channel-adjacent surfaces were identified throughout the Middle River below
Devils Canyon as a result of ground-based observation of surface heights as well as the
vegetation assemblage. Using turnover analysis results, the terrace surfaces were evaluated for
main channel erosion (i.e., bank retreat) since the 1950s, dissection of the terrace surface since
its formation (i.e., relationship to formation of side sloughs), and overall percentage of valley
bottom area occupied by the terraces (i.e., the non-fluvial component of the valley floor).
The percentages the terrace units occupy, by geomorphic reach, compared to the overall valley
bottom area, in addition to the percent compared to non-channel valley bottom area, are
presented in Table 5.1-1. The summaries for the erosion and dissection for each geomorphic
reach are presented in Table 5.1-2. These results are part of an initial investigation of
geomorphic surface heights and overtopping frequencies and as such the results are preliminary
and are intended to be updated in a technical memorandum.
As identified in ISR Study 6.5, Part C, Section 7.2.1.1.3 an Upper River Reconnaissance and
Characterization was performed during the 2014 field study season (Section 4.1 Activities 7, 8,
and 9). This effort was conducted by boat between the Denali Bridge at PRM 292 and the
Watana Dam site at PRM 187.1. As part of the characterization effort, lateral controls of the
channel planform, sediment storage zones and the caliber of the stored sediments, erosional
areas, and areas of active landslides (sediment sources) were mapped for the entire Upper
Susitna River Segment.
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In addition, the area between the Denali Bridge and the official start of the Upper River Segment
at the Maclaren River confluence was also characterized. This reconnaissance included
investigating sources of sand that are a volumetrically significant fraction of the sediment load of
the Middle River. Further data on sediment size fractions transported through the Susitna River
Segments were developed as part of Study Component 3 and presented in Tetra Tech 2014b.
These data were collected in the field with a Trimble GeoExplorer 6000 GeoXH GPS unit, noted
in field books, and on field maps and documented with georeferenced photographs. The results
of this effort are summarized in a series of maps; Figure 5.1-1 through Figure 5.1-9. Figures are
referenced by geomorphic reach.
While the area above the Maclaren River confluence is not part of the Study Area (PRM 0- PRM
261.3), this section of the river was still investigated as it contributes sediment and flow to the
Upper River Segment. Thus, the section between the Denali Bridge (PRM 292) and Maclaren
River confluence (PRM 261.3) is noted as the “Upstream of Maclaren River Confluence”
section and is discussed in further detail in Section 5.3.7 of Attachment 1 with representative
photographs presented in Section 1 of Appendix A. Overall, upstream of the Maclaren River
confluence, there is a relatively mild slope of roughly 6 ft/mile, mostly fine-grained lateral
sediment sources with some gravel and cobble, limited presence of mid-channel islands in
expansion zones, with very-low sediment delivering, small tributaries. These geomorphic
variables indicate that delivered sediment composition to the Upper River Segment are mostly
fine-grained materials from active glaciers and fine to coarse-grained materials derived from
erosion and failure of the glacio-fluvial deposits that form the channel banks for most of the
section.
With the absence of bathymetric data in the Upper River Segment, depths of the channel were
estimated with a boat-mounted fathometer during the 2014 reconnaissance and are identified in
Figure 5.1-10 through Figure 5.1-13. Sediment data collected during the 2014 reconnaissance
effort is described and presented in the Study 6.6 Study Implementation Report.
As part of the Upper River Reconnaissance, opportunistic water quality parameters were
collected. This included water depth, water temperature, conductivity, turbidity, and reduction
potential (ORP). The parameters were sampled on a YSI 556MPS water quality meter and
MicroTPW turbidity meter. A summary table of the water quality parameters collected are
compiled in Table 5.1-3.
In addition, geomorphic surface mapping was performed for the remaining 3 Focus Areas (FA-
151 Portage Creek, FA-173 Stephan Lake Complex, and FA-184 Watana Dam). The results of
this mapping effort are presented in Section 5.1 Field Data Collection of the Study 6.6 Study
Implementation Report. This effort included identifying the Geomorphic Assessment Area
(GAAs) (ISR Study 6.5, Part A, Section 4.1.2.3.2) for each studied Focus Area. These
boundaries are compiled in Table 5.1-4.
Activities identified in ISR Study 6.5, Part C, Section 7.2.1.1.3 including integration of ice-
modeling efforts with geomorphic surfaces and system dynamics (Study 7.6) (Section 4.1
Activity 2), integration of data from riparian investigations including vegetation mapping and
aging to better define age constraints in FAs (Section 4.1 Activity 4), and analysis of the spatial
distribution of geomorphic surfaces and channel types within different aged components of the
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FAs (Section 4.1 Activity 5) are part of an ongoing effort. In addition to these characterization
efforts, the technical memorandum Susitna River Historical Cross Section Comparison (Tetra
Tech. 2014a) was filed on September 17, 2014. This technical memorandum provides a
comparison of cross sections that were surveyed in the 1980s with those surveyed in 2012 and
2013. This effort was part of the third task of this study component identified in Study 6.5 RSP
Section 6.5.4.1.2.3.
5.2. Study Component: Bed Load and Suspended-load Data
Collection at Tsusena Creek, Gold Creek, and Sunshine Gage
Stations on the Susitna River, Chulitna River near Talkeetna
and the Talkeetna River near Talkeetna
As identified in ISR Study 6.5 Section 7.1 and Section 7.2.1.2, two prior years (2012 and 2013)
of data collection had been performed by the USGS and the USGS continued to perform
suspended-sediment and bed-load measurements and to the extent that conditions allow, bed-
material samples in 2014. The dates of collected sediment samples in 2014 are compiled in Table
5.2-1. Locations and types of USGS sediment transport data collected for the period of study
from 2012 through 2014 are presented in Table 5.2-2. Tables 5.2-3, 5.2-4 and 5.2-5 provide the
data collected for all three years; 2012, 2013 and 2014; for suspended sediment, bed-load and
bed material, respectively. The reporting of the sediment transport data from the 2012, 2013 and
2014 collected by the USGS completes this study component.
5.3. Study Component: Sediment Supply and Transport Middle and
Lower Susitna River Segments
As identified in ISR Study 6.5 Section 7.2.1.3, a more detailed pre-Project sediment balance for
the Middle Susitna River Segment between the proposed Watana Dam site (PRM 187.1) and the
Three rivers Confluence (PRM 102.4) than presented in an earlier technical memorandum (Tetra
Tech 2013a) using hydraulic and sediment transport modeling results for this portion of the study
area from the 1-D bed evolution model developed in Study 6.6. This task was completed and
reported on in the September 17, 2014 posted Technical Memorandum, Update of Sediment-
Transport Relationships and a Revised Sediment Balance for the Middle and Lower Susitna
River Segments (Tetra Tech 2014b).
To support estimates of the contributions to the sediment supply from mass wasting, bank
erosion and tributaries in the Middle and Lower Susitna River segments (ISR Study 6.5, Part C,
Section 7.2.1.3), aerial videos were collected in August and September 2014. This data collection
effort was conducted in conjunction with aerial reconnaissance of selected reservoir tributaries
identified in the reservoir geomorphology study component (ISR Study 6.5, Part C, Section
7.2.1.8). Opportunistic video of the Susitna River was collected in this process in order to
support identification of mass wasting and sediment supply within the channel for both the
Middle and Lower Susitna River segments. The videos are a mechanism to characterize
tributaries and their contributing watersheds in terms of bed rock controls, lateral sediment
sources, and potential sediment sinks. This data will support a more detailed pre-Project
sediment balance for the Middle and Lower Susitna River segments.
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5.4. Study Component: Assess Geomorphic Change Middle and
Lower Susitna River Segments
This study component was completed in 2014. The results of the completed study are presented
in September 26, 2014 filed technical memorandum Mapping of Geomorphic Features and
Turnover within the Middle and Lower Susitna River Segments from 1950s, 1980s, and Current
Aerials (Tetra Tech 2014c).
5.5. Study Component: Riverine Habitat versus Flow Relationship
Middle Susitna River Segment
This study component was completed in 2014. The results are presented in September 26, 2014
Updated Mapping of Aquatic Macrohabitat Types in the Middle Susitna River Segment from
1980s and Current Aerials (Tetra Tech 2014d).
5.6. Study Component: Reconnaissance-Level Assessment of
Project Effects on Lower and Middle Susitna River Segments
As identified in RSP Section 6.5.4.6.2.4 and ISR Study 6.5 Section 7.2.1.6 a Literature Review
on the downstream effects of dams has been integrated into technical memorandum developed
jointly by the Riparian Instream Flow Study (Study 8.6) and the Geomorphology Study (6.5).
This technical memorandum, the Dam Effects on Downstream Channel and Floodplain
Geomorphology and Riparian Plant Communities and Ecosystems – A Critical Literature
Review (R2 Resource Consultants and Tetra Tech 2014) was filed November 14, 2014. The
results of this effort helped in the development of an initial framework presented in Section 5.11
to qualitatively and semi-quantitatively identify the anticipated trends and levels of project
effects.
As identified in ISR Study 6.5 Section 7.2.1.6, a refinement of the sediment transport assessment
results for the pre-Project condition was performed. This included an update of the rating curves
for bedload transport and suspended-load transport. The results of this effort are presented in the
technical memorandum Update of Sediment-Transport Relationships and a Revised Sediment
Balance for the Middle and Lower Susitna River Segments (Tetra Tech 2014b) filed September
17, 2014. These rating curves were used in the development of the 1-D bed evolution model as
presented in Study 6.6 SIR Attachment 1 2014 Fluvial Geomorphology Modeling Model
Development Technical Memorandum (Tetra Tech 2015b).
In support of the decision as to whether to continue the 1-D bed evolution model downstream of
PRM 29.9, Project related changes in the magnitude of peak flows at Sunshine and Susitna
station and changes in flow duration at Susitna Station were determined based on comparison of
pre-Project and Max LF OS-1b flows. The effort to quantify these changes in flows is a
continuation of the streamflow assessment identified in Study 6.5 ISR Section 4.6.2.1. The
results of this effort are reported in Section 5.1 of the technical memorandum Decision Point on
Fluvial Geomorphology Modeling of the Susitna River below PRM 29.9 (Tetra Tech 2014g) filed
September 26, 2014.
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5.7. Study Component: Riverine Habitat Area versus Flow Lower
Susitna River Segment
This study component was completed in 2013. The results are described in three technical
memoranda filed in 2013: Mapping of Aquatic Macrohabitat Types at Selected Sites in the
Middle and Lower Susitna River Segments from 1980s and 2012 Aerials Technical
Memorandum (Tetra Tech 2013f), Stream Flow Assessment Technical Memorandum (Tetra
Tech 2013d), and Synthesis of the 1980s Lower Susitna River Segment Aquatic Habitat
Information Technical Memorandum (Tetra Tech 2013e).
5.8. Study Component: Reservoir Geomorphology
5.8.1. Reservoir Trap Efficiency and Sediment Accumulation Rates
Estimates of reservoir trap efficiency for this study component were used by the Fluvial
Geomorphology Modeling Study (6.6) to adjust the upstream sediment supply for the 1-D bed
evolution model as described in Study 6.5 ISR, Part C, Section 7.2.1.8. The sediment sizes
routed by the 1-D modeling effort include sand, gravels and cobbles. For these sizes, a trap
efficiency of 100 percent was utilized as estimated in Study 6.5 ISR Section 5.8.1.
An analysis of the potential changes to sediment delivery from the upper Susitna watershed into
the reservoir from glacial surges was performed. The results of this effort are documented in the
technical memorandum Assessment of the Potential for Changes in Sediment Delivery to Watana
Reservoir Due to Glacial Surges filed November 14, 2014 (Tetra Tech. 2014e).
Based on the results of this analysis it was concluded that no further geomorphic investigations
were warranted for flow or sediment production from glacial surges (Tetra Tech 2014e). This
included a recommendation to not include a glacial surge sediment loading scenario in the
reservoir sediment trap efficiency and sediment accumulation modeling in the reservoir trap
efficiency and sediment accumulation rates task (RSP Section 6.5.4.8.2.1) in Reservoir
Geomorphology study component of the Geomorphology Study (6.5).
5.8.2. Delta Formation
As identified in ISR 6.5, Part C, Section 7.2.1.8, an aerial reconnaissance of selected tributaries
was performed during the 2014 field season. These data include aerial reconnaissance videos of
Oshetna River, Goose Creek, Jay Creek, Kosina Creek, Watana Creek, and Deadman Creek. The
aerial reconnaissance of selected reservoir area tributaries for potential delta formation,
performed on September 29, 2014, was carried out under the Delta Formation task. The primary
objective of this reconnaissance was to support planning of field data collection efforts.
Specifically, the potential formation of deltas is expected within the fluctuation zone of the
proposed Watana Reservoir (i.e., between elevations of 1,850 feet and 2,050 feet, NAVD88). In
addition to the aerial reconnaissance, opportunistic ground reconnaissance of the six reservoir
area tributaries was performed during the Upper Susitna River Reconnaissance effort noted in
Section 4.1 of this SIR. A summary of these observations from both reconnaissance efforts is
presented in Table 5.8-1. The reconnaissance information will further support planning of the
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field data collection effort associated with the reservoir tributary deltas (ISR Study 6.5, Part C,
Section 7.2.1.8).
The aerial reconnaissance provided a means to identify locations for field teams deployed in
helicopters to safely access the tributaries near the areas where deltas may form so that sediment,
primarily bed material, can be sampled and channel geometry surveyed. These data will be used
to estimate sediment supplied to the potential deltas so formation of the deltas can be modeled.
Starting from upstream and proceeding downstream, some observations concerning the selected
tributaries are summarized in the following paragraphs. The mouth of the Oshetna River is at an
elevation above 2,050 feet. While the flow in the creek was relatively clear (Figure 5.8-1), the
channel splits in the upstream direction with larger gravel bars and a more active planform,
indicating potential for substantial gravel yield. Safe landing sites and access were noted near the
mouth of the Oshetna River (Figure 5.8-2).
The elevation of the mouth of Goose Creek is about 2,050 feet. Goose Creek flows from a lower
relief valley than the downstream tributaries, and exhibits stable hillslopes and a coarse plane
bed channel (Figure 5.8-3). Safe access was identified at sites on the fan at the mouth of Goose
Creek (Figure 5.8-4).
Jay Creek transports large woody debris and gravel as it flows through a narrow valley (elevated
sediment yield may be driven by landslides and colluvial input from the hillslopes) (Figure 5.8-
5). Safe landing sites were noted on the fan at the mouth of Jay Creek (Figure 5.8-6), upstream
of elevation 1,850 feet and at an elevation of 2,050 feet.
Upon entering Kosina Creek, the multi-channel planform was apparent, which transitions into a
sinuous channel in an unconfined valley in the upstream direction. Safe landing sites were
identified at the confluence with the Susitna River (Figure 5.8-7), near elevations of 1,850 feet
and 2,050 feet.
Large gravel bars, ample large woody debris, and evidence of an active channel transporting
sediment and reworking deposits were observed in Watana Creek (Figure 5.8-8). Along Watana
Creek, many safe landing sites were noted at the confluence with the Susitna River (Figure 5.8-
9) near elevations of 1,850 feet and 2,050 feet.
A steep confined channel was observed in Deadman Creek near the confluence with the Susitna
River (Figure 5.8-10), and the creek opens into an unconfined meadow in the upstream direction.
Safe access was identified at the confluence with the Susitna river (Figure 5.8-11), and within the
reservoir fluctuation zone along Deadman Creek either (1) in the creek channel if flows are low
enough, or (2) on the left bank terrace.
5.8.3. Reservoir Erosion
In 2014, as identified in ISR 6.5, Part C, Section 7.2.1.8 the preliminary results of the Study 4.5
Reservoir Slope Stability Assessment and associated GIS coverages of preliminary soil and mass
wasting conditions around the proposed reservoir site were reviewed to help plan field efforts to
assess potential areas and types of reservoir shoreline erosion. Coordination between the Study
4.5 and the assessment of reservoir erosion (RSP Section 4.5.4.8.2.3) will continue.
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5.8.4. Bank and Boat Wave Erosion downstream of Watana Dam
No work was performed on this task in 2014.
5.9. Study Component: Large Woody Debris
As identified in Study 6.5 ISR Section 7.2.1.9 the large woody debris (LWD) analysis completed
in 2014 included finalizing the inventory of wood from the 1983, 2012, and 2013 aerial
photographs and a field inventory of wood in six LWD sample areas in the Middle and Lower
Susitna River to determine wood loading, input mechanisms, input and transport frequency,
species, and function in the river. Methods followed those described in the RSP.
5.9.1. Aerial Photograph Inventory
LWD and log jams were digitized in the selected areas/geomorphic units listed in the RSP from
the 1983, 2012, and 2013 aerial photographs (Table 5.9-1). The resolution of the 1950s aerial
photographs was not adequate to differentiate LWD. The resolution of the 1980s aerial
photographs upstream of PRM 159.5 was also not adequate to differentiate LWD so no digitizing
was attempted for those years/areas. There were deep shadows in some areas of the channel that
made differentiation of LWD and log jams difficult, particularly along southern shorelines where
tall trees or topography created shadows.
5.9.2. Field Inventory
LWD sample areas at PRM 9-13, FA-151 Portage Creek, PRM 169, PRM 171, FA-173 Stephan
Lake, and FA-184 Watana Dam were inventoried during the summer of 2014. A total of 525
individual pieces of LWD over 20 feet in length and 94 log jams (containing 466 pieces of
LWD) were inventoried within the six LWD sample areas. Figures 5.9-1 through 5.9-5 show the
characteristics of the combined 2013 and 2014 LWD field data. Maps showing the location of
LWD within the six sample areas are included as Figures 5.9-6 through 5.9-11.
5.10. Study Component: Geomorphology of Stream Crossings along
Transmission Lines and Access Alignments
An aerial reconnaissance of the recently identified Denali East access corridor and portions of
the Denali West corridor was made on August 14, 2014 to identify the general geomorphic
condition of streams that the corridor crosses and help with logistical planning of field work at
each crossing. This task was identified in Study 6.5 ISR, Part C, Section 7.2.1.10. The access
routes were flown in a helicopter. A GPS point was taken at each crossing and information on
estimated stream width, confinement, substrate, and the potential for helicopter landing sites was
determined from the air. A photo was also taken of each crossing.
The route of the aerial reconnaissance flight and each stream crossing identified from the air is
shown on Figure 5.10-1. Stream crossings were numbered sequentially as noted on the figure and
correspond to the stream condition information recorded at each crossing in Table 5.10-1. All
have easy helicopter landing zones nearby.
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5.11. Study Component: Integration of Fluvial Geomorphology
Modeling below Watana Dam Study with the Geomorphology
Study
Continual refinement of geomorphic surfaces and interpretation and integration of model results
has been performed between the Geomorphology Study and Fluvial Geomorphology Study in
2014 (ISR 6.5, Part C, Section 7.2.1.11). As identified in Section 4.11, an initial framework for
integration of the Geomorphology Study and the Fluvial Geomorphology Study has evolved
from the hierarchical evaluation of dam impacts presented in the technical memorandum Dam
Effects on Downstream Channel and Floodplain Geomorphology and Riparian Plant
Communities and Ecosystems – A Critical Literature Review (R2 Resource Consultants and
Tetra Tech 2014). The initial framework is used to identify qualitatively and semi-quantitatively
the anticipated trends and levels of Project effects (Table 5.11-1). The Project effects are divided
into First-order (Table 5.11-2), or primary effects related to the Project and Second-order effects
(Table 5.11-3) that result from the First-order change in geomorphic drivers. The trends
(increasing or decreasing) and level of effects (little or no change, or anticipated low, medium, or
high change) are identified for each category of potential effects. Development of the
framework will continue resulting in its refinement, expansion and further quantification as more
study results became available. It is anticipated that results from the Ice Processes in the Susitna
River Study (7.6) and Riparian Instream Flow Study (8.6) will provide valuable information with
which to refine, expand and further quantify the framework.
The integrating framework for the Geomorphology (Study 6.5) and Fluvial Geomorphology
Modeling (Study 6.6), that is based on the hierarchical evaluation of dam effects (R2 Resource
Consultants and Tetra Tech 2014), uses the findings and results of both studies to assess the most
likely Project-induced physical trends in the three Susitna River segments. While most of the
trend trajectories are presented qualitatively or semi-quantitatively, based on existing
information, further results from the 1-dimensional and 2-dimensional bed evolution modeling of
pre- and post-Project scenarios will enable quantification of Project impacts. It is highly unlikely
that any of the Project scenarios will change the trajectory of the trends, but the magnitude of the
individual changes will be dependent on the selected scenarios.
Integration of the Geomorphology (Study 6.5) and Fluvial Geomorphology Modeling (Study 6.6)
study results within the framework of First- and Second-order responses to dams provides the
expected changes to the physical system and hence the physical habitat within the channel and
floodplain system. This in turn provides the basis for assessing Third-order impacts to the
biological communities and the ecosystem and the Fourth-order biogeomorphic feedback
between ecological responses and physical processes that are being investigated within the
Riparian Instream Flow Study (Study 8.6) and Fish and Aquatics Instream Flow Study (Study
8.5), and Study of Fish Barriers in the Middle and Upper Susitna River and Susitna Tributaries
(Study 9.12).
6. DISCUSSION
To date significant progress has been made in achieving the objectives of the Geomorphology
Study (6.5) and its 11 study components. Discussion of the results for each of the 11 study
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components is presented in this section. Much of the progress in conducting these studies has
been presented in the technical memoranda filed in 2012, 2013 and 2014. The Geomorphology
Study 6.5 ISR Part A and its associated appendices also provided considerable information
developed in the studies.
6.1. Study Component: Delineate Geomorphically Similar
(Homogeneous) Reaches and Characterize the Geomorphology
of the Susitna River
The vast majority of this study component has been completed. There is a thorough discussion of
the progress in Study 6.5 ISR Section 6.1 through the early 2014. Since the reporting in the ISR,
the most significant efforts involved the reconnaissance of the Upper Susitna River Segment and
the associated update of the Geomorphic Reach Delineation and Characterization, Upper,
Middle and Lower Susitna River Segments – 2015 Update include as Attachment 1 to this SIR
(Note: Two earlier versions of this technical memorandum were filed in 2013 [Tetra Tech 2013a
and 2014 (Tetra Tech 2014a)].
The Upper River reconnaissance effort was conducted to better understand the conditions
upstream of the Watana Dam site that currently result in the upstream sediment supply to the
Middle Susitna River segment. From this effort is was determined that the source of the large
sand load in the Susitna River is primarily the glaciated watersheds upstream of the Middle
River. In addition, through observations on this trip and in conducting field work in the Middle
and Lower Susitna Rivers, it was determined that there is a progression of the relative influence
of ice processes versus fluvial processes in determining the morphology of the Susitna River. In
the Upper River segment ice processes tend to be dominant. Where coarse bed materials are
present there is extensive paving of the bed and banks and there are extensive coarse grained ice
deposits on the tops of lower terraces and floodplain segments. An ice trim line on the
vegetation is frequently 10 to15 feet above the low-water surface. In the Middle River Segment
the form and dynamics of the various order channels, bars and islands as well as floodplains and
terraces are the result of the combined effects of both ice and fluvial processes. Ice processes,
including ice damming and ice-jam failures, appear to be more important in alluvial reaches
located upstream of valley floor constrictions. In the Lower River Segment, while ice processes
occur, the widths of the valley bottoms tends to mitigate their effects, and hence the segment is
fluvially dominated.
The 2014 field season allowed mapping of geomorphic surfaces in the 3 Focus Areas upstream
of Portage Creek to complete the effort that was started in 2013 with the mapping of the 7 Focus
Areas downstream of Portage Creek.
On September 17, 2014 the technical memorandum Susitna River Historical Cross Section
Comparison (Tetra Tech. 2014a) was filed. This technical memorandum provides a comparison
of cross section that were surveyed in the 1980s with those surveyed in 2012 and 2013. This
information has been used by the Fluvial Geomorphology Modeling Study (6.6) to help in the
validation of the 1-D bed evolution model in the Middle Susitna River segment. A significant
conclusion from the technical memorandum relates to the relatively small amount of cross
section change over the past three decades. In the conclusions of the technical memorandum
(Tetra Tech 2014a) it is stated:
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Overall, the results show that the Middle Susitna River was generally stable in terms of
bed elevation change over the 3 decade period between the 1980s studies and the current
effort. Changes were typically on the order of several feet or less and there was not a
consistent trend toward aggradation (bed elevation increase) or degradation (bed
elevation decrease) throughout the Middle River segment. The area with the most
consistent trend were geomorphic reaches MR-7 and MR-8 in which the majority of the
length was aggradational; however, there were still cross sections within these two
reaches that showed degradation over the period of comparison. MR-2 showed the least
change, with all cross sections having minimal change in bed elevation and area with the
exception of the cross section at PRM 179.5, which aggraded by 2.3 ft and increased in
area by 490 sq. ft. The remaining reaches had more of a mix between aggradation and
degradation.
With the completion of the updated technical memorandum (Attachment 1) and the Technical
memorandum on historical cross section comparison (Tetra Tech 2014a), the overall objective of
this study component to “Geomorphically characterize the Project-affected river channels and
floodplain” and the specific objectives listed in the 4 sub-bullets in Section 2 have been largely
met. Work remaining involves further development of the characterization by interaction with
others studies as results of their analysis and modeling efforts become available. Of particular
importance are findings from the Fluvial Geomorphology Modeling Study (6.6), Riparian
Instream Flows Study (8.6), and the Ice Processes in the Susitna River Study (7.6).
6.2. Study Component: Bed- and Suspended-load Data Collection at
Tsusena Creek, Gold Creek, and Sunshine Gage Stations on
the Susitna River, Chulitna River near Talkeetna and the
Talkeetna River near Talkeetna
A thorough discussion of this effort based on the data collected in 2012 and 2013 was presented
in the Study 6.5 ISR Section 6.2. Since that discussion, the USGS collected the 2014 sediment
transport data. The collection of data in 2014 provides and additional year of data not originally
anticipated in the RSP (Section 6.5.4.2). Using the sediment transport earlier USGS data from
the 1980s along with the 2012 and 2013 data, the Fluvial Geomorphology Study has been able to
develop a 1-D bed evolution model that extends from the Watana Dam Site (PRM 187.1)
downstream to Susitna Station (PRM 29.9). The development, calibration and validation of this
model are presented in Attachment 1 to the Study 6.6 SIR (Tetra Tech 2015b). The 1980s and
current data have also provided the basis for analysis of sediment transport related issues in five
technical memoranda [(Tetra Tech 2013a), (Tetra Tech 2013c), (Tetra Tech 2014b), (Tetra Tech
2014g), and (Tetra Tech 2015b)].
With the delivery of the 2014 sediment transport data by the USGS, this study component is
complete and the study objective to, “Collect sediment transport data to supplement historical
data to support the characterization of Susitna River sediment supply and transport” has been
met.
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6.3. Study Component: Sediment Supply and Transport Middle and
Lower Susitna River Segments
The Study 6.5 ISR Section 6.3 presents a discussion of the status and progress of this study
component through the spring of 2014. Since the ISR, the primary work in this study component
included an update of the sediment transport relationships developed from the USGS data and an
updated of the sediment balance. Both of these efforts are documented in the technical
memorandum Update of Sediment-Transport Relationships and a Revised Sediment Balance for
the Middle and Lower Susitna River Segments filed September 17, 2014 (Tetra Tech 2014b). The
updated sediment transport relationships were used in the development, calibration and
validation of the latest version of the 1-D bed evolution model presented in Attachment 1 to the
Study 6.6 SIR (Tetra Tech 2015b).
As part of this effort, the sediment transport data collected by the USGS in 2012 and 2013 were
added to the data collected in the 1980s. In Tetra Tech (2014b) it was concluded from the plots
of the various components of the sediment load (bedload, suspended load, total load) combined
1980s and current data that, “The data collected in 2012 and 2013 are very similar to previous
data.” It is noted that the results of the 2014 data collected by the USGS were not available at the
time the technical memorandum was developed. This data will be plotted with the previously
collected 1980s, 2012 and 2013 data and the comparison repeated to again evaluate whether the
relationships need to be updated for the 2014 data. It is further indicated in Tetra Tech (2014b):
Although the regression analyses included in this TM generally produce lower slopes
than the earlier USGS relationships, it is the improved method of analysis, rather than
the data, that produces the change. The sediment rating curves were updated to include
all the data and are considered more representative of transport conditions than the
earlier rating curves. The data and rating curves are sufficient for all remaining
analyses.
Another important finding that helps advance the understanding of the Susitna River sediment
transport conditions and the development of the modeling performed in Study 6.6 were the
findings Tetra Tech (2014b) concerning tributary sediment loading in the Middle Susitna River
segment.
A significant change in this analysis from the initial sediment balance analysis (Tetra
Tech 2013a) is in the estimates of ungaged tributary loads. In the initial sediment
balance the loads were estimated based on assuming sediment loading in proportion to
drainage area. This is appropriate for reasonably similar basin conditions, but in this
instance does not address differences in glaciated versus non-glaciated basins. Field
observations indicate that other than the Chulitna, Talkeetna, and Yentna Rivers, the
Middle and Lower River tributaries are clearwater supplying virtually no wash load and
little sand to the Susitna River. Data were collected by the USGS at Portage Creek and
Indian River in 1984 and are presented in Table 6.0-1. These data are in significant
contrast to the mainstem sediment conditions. Where the mainstem and major tributaries
are dominated by wash load and sand with orders of magnitude less gravel, the Middle
River tributaries have negligible amounts of wash load (silt/clay), slightly higher
amounts of sand, and yet larger amounts of gravel. (Tetra Tech 2014b)
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Since the submittal of the ISR, significant progress has been made in meeting the objective of
this study component to “Determine sediment supply and transport in Middle and Lower Susitna
River Segments.” Important progress that support the objectives include determination that the
2012 and 2013 sediment transport data collected by the USGS are comparable to data collected
in the 1980s, development of revised sediment transport relationships that have been successfully
used to support development of the 1-D bed evolution model, and update of the sediment balance
that provides a better understanding of the contribution of tributaries to sediment loading within
the Middle Susitna River segment. Efforts remaining to complete the study will further add to the
robustness and utility of the information produced by this study component. These activities
include an update of the sediment balance to include tributary data collected in 2014 and
estimates of sediment loading from mass wasting and bank erosion to be developed from the
turnover analysis (Tetra Tech 2014c), and comparison of the 1980 sediment transport data to
data collected in 2014 by the USGS. In terms of the latter item, the sediment transport
relationships will be revised if the comparison indicates adjustment is warranted. Based on the
previous comparison of the 2012 and 2013 sediment transport data with the 1980s data, it is
expected that adjustment of the relationships will not be necessary.
6.4. Study Component: Assess Geomorphic Change Middle and
Lower Susitna River Segments
Since the spring of 2014 and the filing of the ISR the technical memorandum Mapping of
Geomorphic Features and Turnover within the Middle and Lower Susitna River Segments from
1950s, 1980s, and Current Aerials (Tetra Tech. 2014c) was filed September 26, 2014. This
technical memorandum and the effort associated with producing it completed the Assess
Geomorphic Change in the Middle and Lower Susitna River Segments study component. This
effort was an update to an earlier technical memorandum Mapping of Geomorphic Features
within the Middle and Lower Susitna River Segments from 1980s and 2012 Aerials (Tetra Tech
2013g). There were two major updates to the technical memorandum. The first was the extension
of the period of channel documentation by an additional 30 years through acquisition, processing
and incorporation of 1950s aerial photographs. The second update involved inclusion of a
turnover analysis. Both of these study components were included in the RSP (Study 6.5 RSP
Section 6.5.4.4.2) as a result of consultation with licensing participants. Other less substantial
updates included items indicated in Study 6.5 ISR, Part C, Section 7.2.1.4.
The turnover analysis provided both a qualitative visual and numerically quantifiable method of
describing geomorphic change in the Middle and Lower Susitna River segments. When
comparing channel or floodplain features over time, increases in vegetation and narrowing of
channels is associated with net channel to floodplain turnover. A net floodplain to channel
turnover indicates an increase in channel width and a removal of vegetation by erosion. As each
geomorphic reach varies in length, turnover was presented as normalized rates so that turnover in
different geomorphic reaches could be compared to each other. Turnover rates were calculated
by dividing the calculated turnover areas by the length of each reach and the span of time
between each set of aerials: 30 years for the 1950s to 1980s and 1980s to 2012 analyses, and 60
years for the 1950s to 2012 analysis. Some of the conclusions from the technical memorandum
(Tetra Tech 2014c) are summarized below:
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The previous technical memorandum (Tetra Tech 2013g) identified increased vegetation
as the primary factor in geomorphic change, the turnover analysis described in this
technical memorandum further validates that conclusion, identifying greater channel to
floodplain turnover throughout the Middle and Lower Susitna River segments.
In the Middle River, net channel to floodplain turnover rates increased between the
periods of the 1950s to 1980s and the 1980s to 2012 for MR-4 through MR-8. Net
channel to floodplain turnover rates decreased in MR-1 through MR-3 over the same two
periods.
Compared to the Middle River, the Lower River had a stronger trend of increasing
channel to floodplain turnover between the two periods of the 1950s to 1980s and 1980s
to 2012. Five out of six of the Lower River geomorphic reaches had an increase in net
channel to floodplain rate between those two periods. LR-4 was the exception. During the
1950s to 1980s, LR-2 and LR-4 were the only Lower River reaches to have a net channel
to floodplain turnover rate. For comparison, during the 1980s to 2012 period, LR-1, LR-
2, LR-3, LR-4, and LR-6 all had net channel to floodplain turnover rates.
Among the Middle River geomorphic reaches, MR-6, MR-7, and MR-8 exhibited the
greatest amounts of turnover during the period of the 1980s to 2012. The net channel to
floodplain turnover rate exceeded 7,000 ft2/yr/mile between 1980s to 2012 for MR-6,
MR-7, and MR-8. All the other Middle River geomorphic reaches had net turnover rates
less than 4,000 ft2/yr/mile.
The mapping of channel change that occurred between 2012 and 2013 indicates that
erosion was the primary process contributing to channel change in LR-1, the Middle
River and the Three Rivers Confluence, as opposed to vegetation establishment or
encroachment. These two sets of recent aerial photographs provide an understanding of
short-term channel change in relation to a large flow event.
The technical memorandum Mapping of Geomorphic Features and Turnover within the Middle
and Lower Susitna River Segments from 1950s, 1980s, and Current Aerials (Tetra Tech 2013c)
represent the completion of the goals and objectives listed in RSP Study 6.5 Section 6.5.4.4 and
ISR Study 6.5, Part C, Section 7.2.1.4 “Assess Geomorphic Change Middle and Lower Susitna
River Segments.” The turnover results data presented in this 2014 technical memorandum have
been used to support the bed evolution modeling and evaluation of the bank energy index in ISR
Study 6.6 Section 7.2.2.1 and documented in Tetra Tech 2015b. The information will also
support the finalization of the sediment balance as part of this Study (See Section 6.3 above), the
Riparian Instream Flow Study (Study 8.6), and Ice Processes Study (Study 7.6).
6.5. Study Component: Riverine Habitat versus Flow Relationship
Middle Susitna River Segment
A thorough discussion of this effort based on the data collected and analysis performed in 2012
and 2013 was presented in the Study 6.5 ISR Section 6.5. Since early 2014, three activities
identified in Study 6.5 ISR Section 7.2.1.5 were performed to complete this study component.
The activities included increasing the percentage of the Middle River below Devils Canyon
mapped for aquatic macrohabitat from 50 percent to 100 percent, updating the macrohabitat
analysis presented in Tetra Tech (2013f) based on the additional mapping, and coordination with
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Studies 9.9 and 8.5 to ensure consistency between the macrohabitat types mapped across the
three studies. The results of the 2014 efforts are documented in the update to the 2013 technical
memorandum filed September 26, 2014 and titled Updated Mapping of Aquatic Macrohabitat
Types in the Middle Susitna River Segment from 1980s and Current Aerials. The filing of this
technical memorandum completed the Riverine Habitat versus flow Relationships Middle
Susitna River Segment component of the Geomorphology Study (6.5).
As a result of analysis of the aquatic macrohabitat mapping performed in 2012, AEA concluded
that there had been considerable change in the area of the various aquatic macrohabitat type at
specific location within the Middle River that the aerial photography of the 1980s was not an
accurate representation of current macrohabitat types at specific locations within the Middle
Susitna River. Based on the original objective of this study component to characterize the surface
area versus flow relationships for riverine macrohabitat types (1980s main channel, side chann el,
side sloughs, upland sloughs, tributaries and tributary mouths) over a range of flows in the
Middle Susitna River Segment, additional aerial photographs would be collected to establish
current aquatic macrohabitat area versus flow relationships. Subsequently, AEA also concluded
that aerial photography collected at multiple specified discharges to develop macrohabitat versus
flow relationships was not necessary for meeting the overall objectives of the Study Plan as the
combination of the 2-D hydraulic modeling, bathymetry and topography collected in the Focus
Areas will provide direct determination of the area of the various macrohabitat types over the
range of flows of interest. Therefore, development of macrohabitat area versus flow relationships
from aerial photographs collected at specified discharges as identified as a goal of this study
component are not needed. This change to the objectives and methods of this study component
was presented as a variance in Study 6.5 ISR, Part A, Section 4.5.3 and as a proposed
modification to the Study Plan in Study 6.5 ISR, Part C, Section 7.1.2.5.
Though the original specific objectives of the study component were not met, this will not
interfere with AEA’s ability to meet the overall objectives of the Geomorphology Study (6.5)
since the modeling approach adopted by fluvial geomorphology Modeling Study (6.6) will
provide more rigorous information than the aquatic macrohabitat area versus flow relationships
that would have been developed under the original objectives. However, the effort does provide
useful information on how aquatic macrohabitat areas have changed at specific locations
between the 1980s and present in relation to the evolution of the various geomorphic features
and channel change. For example, in Tetra Tech (2013f) it was determined that aquatic
macrohabitat changes in the Middle River due to changes in morphology were primarily related
to the biogeomorphic processes of vegetation establishment and beaver dam building. Overall,
these processes contributed to a 42 percent reduction in side slough habitat and an18 percent
reduction in upland slough habitat for 17 sites studied. Other noticeable physical changes
included minor variation in channel location (bank erosion or accretion) or width between the
1983 and 2012 aerials. Localized main and side channel narrowing appears to have been caused
by sediment deposition within the Middle Susitna River Segment habitat sites and changed the
amount of habitat area available in a few sites.
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6.6. Study Component: Reconnaissance-Level Assessment of
Project Effects on Lower and Middle Susitna River Segments
This effort has been divided into 4 tasks: streamflow assessment, sediment transport assessment,
framework for identification of geomorphic reach response and literature review on downstream
effects of dams. Much of the early work was part of the 2012 studies and was geared to provide
information to guide development of the RSP and to support the decision on whether to extend
the downstream limits of the Fluvial Geomorphology Modeling Study (6.6) downstream of PRM
79 (9 miles downstream of Sunshine) to PRM 29.9 (Susitna Station). In all, three technical
memoranda were produced as part of the effort from 2012 through early 2014 as documented in
Study 6.5 ISR Sections 5.6 and 6.6. These technical memorandums were: Development of
Sediment Transport Relationships and an Initial Sediment Balance for the Middle and Lower
Susitna River Segments (Tetra Tech 2013a), Reconnaissance Level Assessment of Potential
Channel Change in the Lower Susitna River Segment (Tetra Tech 2013c), and Stream Flow
Assessment (Tetra Tech 2013d).
As a result of analyses of six criteria, AEA confirmed that geomorphic studies would be
expanded into a portion of the Lower River Segment. During the February 14, 2013 TWG
meeting, this decision was noted and an initial plan presented for commencing such studies in
2013 and completing the studies in 2014 (R2 2013). The sixth criterion considered in defining
the downstream extent of the study area in the Lower River Segment was based on the
Reconnaissance Level Assessment of Potential Channel Change in the Lower Susitna River
Sediment (Tetra Tech 2013c). This technical memorandum evaluated potential Project-related
changes in morphology of the Lower River to determine whether portions of the Fluvial
Geomorphology Modeling Study and other studies need to be extended downstream in the
Lower River. Results from the evaluation served as the basis for the conclusion that the 1-D Bed
Evolution Modeling should be extended approximately 50 miles farther downstream to Susitna
Station (PRM 29.9). This conclusion was based largely on initial results suggesting the portion
of the Lower River Segment below Sunshine could tend toward degradation and channel
narrowing, which warranted more detailed analyses to further investigate potential Project effects
below Sunshine (PRM 88).
Since early 2014, significant additional progress has been made toward the completion of this
study component. The effort is documented in the two technical memorandums Update of
Sediment-Transport Relationships and a Revised Sediment Balance for the Middle and Lower
Susitna River Segments filed (Tetra Tech 2014b) filed September 17, 2014 and Dam Effects on
Downstream Channel and Floodplain Geomorphology and Riparian Plant Communities and
Ecosystems – A Critical Literature Review (R2 and Tetra Tech 2014) filed November 14, 2014.
This work was identified in Study 6.5 ISR, Part C, Section 7.2.1.6. The latter technical
memorandum (R2 and Tetra Tech 2014) was prepared jointly between the Riparian Instream
Flow Study (8.6) and the Geomorphology Study (6.5). It includes a draft First- and Second-order
analysis of dam effects on river morphology which is being expanded on in Study Component 11
(Section 6.11). The former technical memorandum (Tetra Tech 2014b) supported development
of the 1-D bed evolution model and its subsequent application to provide metrics to base the
discussion on whether to extend the 1-D bed evolution modeling downstream of Susitna Station
(PRM 29.9). The actual application of the model was performed in the Fluvial Geomorphology
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Modeling Study (6.6) and the application and decision to not extend the modeling downstream of
Susitna Station is documented in the technical memorandum Decision Point on Fluvial
Geomorphology Modeling of the Susitna River below PRM 29.9 (Tetra Tech. 2014g) filed
September 26, 2014.
Efforts remaining in this study component involve support in interpreting results from the
modeling efforts in the Fluvial Geomorphology Modeling Study (6.6). This includes continued
application of the First- and Second-order framework to support evaluation of geomorphic reach
response as 1-D bed evolution model results for post-Project scenarios become available and
performing a concurrent flow and stage analysis in the Three Rivers Confluence area (Study 6.5
ISR, Part C, Section 7.2.2.6).
Based on the work conducted to date, the objective of this study component to “Conduct a
reconnaissance-level geomorphic assessment of potential Project effects on the Lower and
Middle Susitna River Segments considering Project-related changes to stream flow and sediment
supply and a conceptual framework for geomorphic reach response” has been met and exceeded.
The approach and tools developed for the initial assessment have proven valuable to subsequent
evaluation of modeling results to interpret potential Project effects.
6.7. Study Component: Riverine Habitat Area versus Flow Lower
Susitna River Segment
This study component was completed in 2013 and no work was conducted in 2014. A thorough
discussion of the results of this study component were presented in Study 6.5 ISR, Part A,
Section 6.7.
6.8. Study Component: Reservoir Geomorphology
As described in Study 6.8 ISR Section 7.2.1.8 minor activities in three of the four tasks in this
study component were conducted in 2014.
6.8.1. Reservoir Trap Efficiency and Sediment Accumulation Rates
Estimates of sediment trap efficiency from 2013 of 100 percent for sands, gravels and cobbles
were confirmed for use in the 1-D bed evolution modeling conducted in the Fluvial
Geomorphology Modeling Study (6.6) in 2014.
An analysis of the potential changes to sediment delivery from the upper Susitna watershed into
the reservoir from glacial surges was performed. The results of this effort are documented in the
technical memorandum Assessment of the Potential for Changes in Sediment Delivery to Watana
Reservoir Due to Glacial Surges filed November 14, 2014 (Tetra Tech. 2014e); the following
conclusions were presented:
Two large surging-type glaciers with a surge cycle of about 50 years are located within
the Upper Susitna River Basin. The West Fork Glacier surged in 1935/1937 and again in
1987/1988. The Susitna Glacier surged in 1952/1953 and was expected to surge again in
the first decade of the 21st century. The fact that it has not surged again could be taken as
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evidence that surging is not required to maintain glacial equilibrium under the warming
climatic regime (W.D. Harrison, personal communication, 2012). However, the effects of
climate warming on the frequency and magnitude of glacial surge cycles are as yet
unknown (Turrin 2014).
Glacial surges result in increased ablation losses and increased runoff from the glacier.
Analysis of the hydrologic record at the USGS Gold Creek gage indicated that the
1952/1953 and 1987/1988 surges had no apparent effect on either the mean annual
discharge, the average May-September discharge or the maximum daily discharge and
thus would have had no significant influence on the volume of sand transported to the
Watana Reservoir.
Glacial surges also increase the suspended sediment discharge from the glacier for
relatively short periods of time by an order of magnitude. Measurements at the outlet to
the West Fork Glacier during the 1987/1988 surge indicated suspended sediment
concentrations of up to 30,000 ppm which is an order of magnitude higher than under
non-surge conditions (3-4,000 ppm) and 30 times higher than the average measured
annual suspended sediment concentration (1,000 ppm) at the USGS Denali gage under
non-surge conditions.
If a glacial surge was to occur within the Upper Susitna Basin that is very conservatively
estimated as producing 30,000 ppm concentrations for an entire open water flow period
(OWFP) during the year, then the elevated silt-clay fraction of the annual suspended
sediment load could result in 55 years of sediment delivery to the proposed Watana
Reservoir within a 50 year period. This could reduce the longevity of the dead storage
pool of the reservoir by approximately 10 percent from 850 to 770 years. If the elevated
concentrations are applied to the measured duration of approximately 2 weeks, the surge
could reduce reservoir dead storage pool longevity by about 1 percent (850 to 840 years).
Based on this review and evaluation, no further geomorphic investigations are warranted
for flow or sediment production from glacial surges. This includes a recommendation to
not include a glacial surge sediment loading scenario in the reservoir sediment trap
efficiency and sediment accumulation modeling.
6.8.2. Delta Formation
Aerial reconnaissance provided determination that all six of the tributaries within the reservoir
zone can be access by helicopter both in the fluctuation zone as well as at their current
confluence with the Susitna River. This information will help plan field activities. In addition,
the observations on conditions in the tributaries in relation to the potential for sediment
production and delta formation will also be useful in planning the field activities.
6.8.3. Reservoir Erosion
Coordination between the Geology and Soils Characterization Study (4.5) (RSP Section
4.5.4.8.2.3) and the assessment of reservoir erosion task provided information that will be used
in planning field activities. The coordination between the two studies and data/analyses to be
performed will support the study objectives of analyzing the effect of proposed reservoir
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operations on erosion and mass wasting as well as developing appropriate protection, mitigation
and enhancement measures (PMEs) for erosion.
6.8.4. Bank and Boat Wave Erosion Downstream of Watana Dam
No work on this task was performed in 2014.
6.9. Study Component: Large Woody Debris
The large woody debris (LWD) study component in 2013 and 2014 included two data collection
strategies: an inventory of LWD from 1983, 2012, and 2013 aerial photographs; and a field
inventory of LWD in selected sample areas to provide more detailed data on LWD
characteristics. A total of 5,295 individual pieces of LWD were counted on the 2012/2013
aerials between the mouth and PRM 263. The majority of the wood in the Middle River was
located along the margins of the channel; in the lower river the majority was located on mid-
channel bars. During the LWD field inventory, total of 2,115 individual pieces of LWD over 20
feet in length and 405 log jams (containing an additional 3,107 pieces of LWD) were inventoried
in the Middle and Lower Susitna River. These wood data show that the size, species, decay
class, and source/input mechanism of LWD in the Susitna River changes along the river,
providing important insights into how LWD may be affected by Project operations.
The species of LWD shifted from primarily White Spruce upstream of PRM 181 to a mix of
Balsam Poplar and Spruce between PRM 169-181 to primarily Balsam Poplar downstream of
PRM 151. Concurrently, the dominant input mechanism for LWD was ice processes upstream of
PRM 151, and bank erosion downstream of PRM 151. These data reflect the geomorphology of
the river system as it shifts from a confined river with White Spruce-lined banks upstream of
approximately PRM 151 to a wider, alluvial system with a broad floodplain populated by Balsam
Poplar that enter the river by bank erosion processes. The majority of LWD was located on the
sides of the channel or bars above the low flow wetted channel. The wood generally did not have
an obvious aquatic habitat function, but pieces with large root wads did form scour pools, and
pieces in upland or side sloughs were more stable and provided cover. Some wood was observed
to move at flows over approximately 30,000 cfs (measured at the Gold Creek gage), and pieces
of LWD in the main channel had been moved downstream between the 2013 and 2014 field
seasons, likely the result of pushing by ice.
These data provide information on the location, species, size, input mechanism, and function of
large woody debris in the Susitna River downstream of the proposed dam site which is a goal of
the LWD study component. These data, in combination with field data collection to be
performed between PRM 184-263, will provide the necessary information to assess current LWD
input, loading, and function in the Susitna River as well as potential effects of the proposed
Project facilities and operation on LWD in the system.
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6.10. Study Component: Geomorphology of Stream Crossings along
Transmission Lines and Access Alignments
The assessment of the geomorphology of stream crossings along transmission lines and access
alignments has not been performed. The reconnaissance information collected in 2014 will be
used to plan appropriate field access and field equipment needs for each crossing.
6.11. Study Component: Integration of the Fluvial Geomorphology
Modeling below Watana Dam Study with the Geomorphology
Study
The framework developed from the First- and Second-order elements of the dam effects
technical memorandum (R2 Resources and Tetra Tech 2014) provides the vehicle with which to
integrate the results of the Fluvial Geomorphology and Fluvial Geomorphology Modelling
studies and apply them to qualitative and semi-quantitative prediction (Table 5.11-1) of the
Project effects on the Upper, Middle and Lower River Segments.
First-order effects are summarized in Table 5.11-2. First-order drivers for geomorphic change
include: hydrology, sediment supply, ice processes and geology. The Upper River produces
about 16 percent of the average annual flow of the Susitna River at the Susitna Station gauge, but
since it is located upstream of the reservoir it will be unaffected by hydrologic changes and
hence there will be no hydrologic (peak or base flow) effects on the morphology of the river. In
contrast, within the Middle River Segment peak flows will be reduced by about 40 percent and
base flows will be increased by an as yet undetermined amount that will depend on selected
operational scenarios (Tetra Tech 2013d and Tetra Tech 2014g). Reductions in peak flows are
likely to result in a moderate reduction in channel size, most likely the result of vegetation
encroachment into the channel, but this could be counteracted by ice processes depending on the
Project ice regime (Dam Effects on Downstream Channel and Floodplain Geomorphology and
Riparian Plant Communities and Ecosystems – A Critical Literature Review (R2 Resource
Consultants and Tetra Tech 2014), Moderate increases in base flows are unlikely to have any
significant effects on channel morphology since they are below thresholds for sediment transport
(SIR Study 6.6). An approximately 20 percent reduction in peak flows in the Lower River
segment is likely to have a low impact on channel morphology, and the low, but as yet
undetermined increase, in base flows is likely to have very little effect on channel morphology.
Approximately 11 percent of the average annual bed material load of the Susitna River at Susitna
Station gauge is derived from the Upper River segment, but more importantly, 99 percent of the
Upper River bed material load is composed of sand and only 1 percent is gravel (Tetra Tech
2014b). The Upper River morphology will be unaffected by the Project except in the localized
area of the delta at the upstream end of the reservoir. In the Middle River segment, the channel
morphology is likely to experience little impact from the reduction in sediment load since the
amount of gravel and cobble supplied to and trapped in the dam is quite low. The bulk of the bed
material load supplied to the reservoir is sand which does not contribute significantly to the
channel boundary materials (Tetra Tech 2014b). However, the reduction in sand delivery from
the Upper River is likely to have a moderate effect on floodplain/island construction in the
Middle River because the bulk of the floodplain sediments are sand sized and finer. The
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reduction of the sand fraction in the Middle River will likely not result in channel narrowing as a
result of sediment deposition, although vegetation encroachment could result in channel
narrowing. Although about 92 percent of the average annual bed material load above the Three
Rivers confluence under existing conditions is composed of sand, the Middle Susitna River only
contributes about 27 percent of the sand load at the Three Rivers confluence (Tetra Tech 2014b).
Therefore the reduction in sand due to the Project is likely to have a minor morphological effect
on the Lower River because the combined input of sand from the Chulitna and Talkeetna Rivers
represents about 73 percent of the average annual sand load at the Sunshine gauge. In terms of
gravel contributions, the other component of the bed material load, at the Three Rivers
confluence the Chulitna supplies 87 percent the Talkeetna 9 percent and the Susitna River the
remaining 4 percent (Tetra Tech 2014b); therefore, the Project effects will be even less on the
gravel supply than on the sand supply below the Three Rivers confluence.
Reductions in peak flow and the sediment supplied by the Chulitna and Talkeetna Rivers are
likely to result in a channel narrowing of about 10 percent in the Lower River (Tetra Tech 2013d
and Tetra Tech 2014g). Downstream of the Yentna River confluence the Project effects are
likely to be even further muted because the Yentna River produces about 40 percent of the
average annual flow and 55 percent of the average annual bed material load at the Susitna Station
gauge. Estimates of Project related channel narrowing below the Yentna River Confluence are
reduced to about 5% of the current channel width (Tetra Tech 2014g).
The role of ice and fluvial processes in shaping the river morphology varies with the segment in
question. Based on field observations, the Upper River is an ice-dominated regime (Tetra Tech
2015a), whereas the Middle River has a mixed fluvial and ice regime and the Lower River is
fluvially dominated. The Project will have no influence on ice processes in the Upper River,
except locally at the head of the reservoir. In the Middle River, the Project is likely to delay
freeze up and the ice cover will be less extensive but there are likely to be only minor effects on
river morphology. During break up there will be no Project effects on the Upper River and the
potential morphologic effects on the Middle River will depend on whether the break up is
thermal or dynamic. In either case, there are likely to be only low to moderate impact s on river
morphology. A reduced ice regime on the Middle River is likely to reduce the impacts of ice
processes on channel avulsions, bank erosion and overbank sedimentation. However, experience
with other cold regions hydropower project operations suggest that the ice regimes both at freeze
up and break up can be manipulated by Project operations (HDR 2014, R2 Resource Consultants
and Tetra Tech 2014). There are likely to be no ice-related effects on the morphology of the
Lower River.
The potential for morphological responses to the Project depends to a large extent on the lability
(Grant et al. 2003) or sensitivity (Schumm 1991) of the river and two of the determinants of
lability or sensitivity are the erodibility of the bed and banks as influenced by their cohesiveness
and/or the prevalence of bedrock or other less erodible materials and the opportunity for lateral
mobility as determined by the overall width and topography of the valley floor. The Upper River
segment is laterally and vertically constrained by extensive bedrock outcrop and the presence of
extensive glacial deposits that significantly affect the adjustability of the river. Similarly, the
presence of both bedrock outcrop and coarse grained glacial deposits constrain the Middle River
segment that lies within a relatively narrow valley (Tetra Tech 2015a). Further, within the
Middle River, there are extensive coarse boulder lag deposits within the river bed that
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significantly reduce the potential for bed mobilization and vertical change (Tetra Tech 2015a and
2015b) and thus the potential for Project impacts on the river morphology. The large tributaries
within the Lower River segment, the Chulitna and Talkeetna rivers at the upstream end and the
Yentna River near the downstream end, exert the dominant control on the morphology of the
river that is less constrained by the presence of coarse grained glacial deposits or bedrock
outcrop and occupies a much wider valley than the Upper and Middle rivers.
Second-order effects are summarized in Table 5.11-3. The Second-order effects result from the
changes in the primary First-order drivers that included hydrology, sediment supply and ice
processes and are reflected in the channel and floodplain morphology and connectivity as well as
fluvially-driven hydraulics and sediment transport processes. With the exception of the reservoir
pool, where there will be about 3,000,000 tons of sediment deposited annually (Study 6.5 ISR
Part A Section 5.8.1), there will be no Second-order impacts in the Upper River segment. In the
Middle River Segment, channel impacts are likely to include minor aggradation of gravel,
primarily at or downstream of tributary confluences, reduced channel width as a result of
vegetation encroachment into the channel and moderately to highly reduced flow/sediment
variability as reflected by the ratios of the 2-year peak flows pre- and post-Project and the pre-
and post-Project sediment loads (Tetra Tech 2014g). In the Middle River, the bed material load
will be reduced, primarily as a result of the significant reduction in the volume of sand available
for transport. In the Lower River segment, channel effects are limited because of the tributary
contributions of both sediment and water. Existing aggradational trends will continue, but the
rate of aggradation is likely to be reduced (Tetra Tech 2014g). Channel width is likely to be
reduced by about 10 percent because of the availability of sand required for deposition and
stabilization by vegetation. Flow/sediment variability effects are muted by the tributary
contributions of both flow and sediment (Tetra Tech 2014g).
The Project will have no impacts on the floodplain and floodplain-related processes, accretion,
erosion and inundation, in the Upper River Segment. In the Middle River Segment, the
substantial reduction in the sand supply will likely have a moderate impact on floodplain and
island formation. Erosion rates are likely to be reduced due to the reduction in peak flows and
the frequency and duration of inundation of floodplain/island surfaces will be reduced during the
open-water season. However, depending on the ice regime, especially during break up,
inundation of geomorphic surfaces could either be increased or decreased. In the Lower River
segment, there is unlikely to be a significant impact on either the floodplain or floodplain
processes because of the mitigating influence of the sediment supply from the large tributaries.
The Project will have no impact on the planform of the Upper River segment expect in the area
of delta formation at the upstream end of the reservoir. Depending on the ice-regime the number
of low-order channels (sloughs and side channels) could be reduced in the Middle River
segment. No impacts on the river planform are expected in the Lower River segment.
In the Upper River segment there will be no Project impacts on turbidity. However, depending
on the season there are likely to be low to moderate impacts on turbidity in the Middle River
segment. During the iced-over period, turbidity is likely to increase as reservoir stored flows are
released. During the open-water period there is likely to be a reduction in the turbidity because
of fine sediment trapping and storage in the reservoir (Tetra Tech. 2014b). There are likely to be
very small increases in the turbidity during the iced-over period and very small reductions in the
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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FERC Project No. 14241 Page 35 October 2015
open-water period within the Lower River Segment because of the mitigating effects of the
tributaries.
Tributary impacts in the Upper River Segment are restricted to the reservoir. Depending on the
volume and timing of sediment supply from the tributary and the reservoir elevation, it is
possible that small transient deltas could form within the reservoir. Modeling of the tributaries
and their delta formation potential will address this issue (Study 6.5 ISR Part A Section 4.8.2.2
Reservoir Geomorphology). In the Middle River Segment, it is likely that there could be minor
tributary impacts related to progradation of the tributary fans into the river and creation of
upstream backwater on the river that could affect upstream water-surface elevations and ice jam
formation. There are unlikely to be any tributary impacts in the Lower River segment.
7. CONCLUSION
In summary, significant progress has been made in 2014. Four of the eleven study components
are now complete including: Bed Load and Suspended-load Data Collection at Tsusena Creek,
Gold Creek, and Sunshine Gage Stations on the Susitna River, Chulitna River near Talkeetna and
the Talkeetna River near Talkeetna (Study Component 2), Assess Geomorphic Change Middle
and Lower Susitna River Segments (Study Component 4), Riverine Habitat versus Flow
Relationship Middle Susitna River Segment (Study Component 5), and Riverine Habitat Area
versus Flow Lower Susitna River Segment (Study Component 7) which was completed in 2013.
One study component, Delineate Geomorphically Similar (Homogeneous) Reaches and
Characterize the Geomorphology of the Susitna River (Study Component 1), is nearly complete,
but requires results from the 2-D hydraulic modeling in the focus areas from Study 6.6 to map
inundation of the geomorphic surfaces. Three study components will continue throughout the
study effort as they participate in the evaluation of post-Project scenarios: Sediment Supply and
Transport Middle and Lower Susitna River Segments (Study Component 3), Reconnaissance-
Level Assessment of Project Effects on Lower and Middle Susitna River Segments (Study
Component 6), and Integration of the Fluvial Geomorphology Modeling below Watana Dam
Study with the Geomorphology Study (Study Component 11). There are three study components
that the majority of the work effort remain to be completed: Reservoir Geomorphology (Study
Component 8), Large Woody Debris (Study Component 9), and Geomorphology of Stream
Crossings along Transmission Lines and Access Alignments (Study Component 10). For these
three studies, 2014 activities involved coordination with other studies and aerial reconnaissance
to support planning of field data collection efforts.
Given the combination of 2012, 2013 and 2014 efforts, variances (see SIR Study 6.5 Section 4),
and the plans for completing Study 6.5 with modifications (see Section 7.2), AEA will achieve
the approved objectives (SIR Study 6.5 Section 2) for the Geomorphology Study.
7.1. Decision Points from Study Plan
There was one decision Points beyond those described in Study 6.5 ISR Part C Section 7.1.1 that
was established and it involved investigation of the potential for increased sedimentation in
Watana Reservoir due to glacial surge. This decision point was established and completed in
2014. The effort associated with this decision point is documented in the technical memorandum
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 36 October 2015
Assessment of the Potential for Changes in Sediment Delivery to Watana Reservoir Due to
Glacial Surges (Tetra Tech 2014e) filed November 14, 2014.
In the February 1, 2013 SPD FERC recommended that in support of the Glacier and Runoff
Changes Study (Study 7.7) that AEA “analyze the potential changes to sediment delivery from
the upper Susitna watershed into the reservoir from glacial surges.” To address the FERC
recommendation in the February 1, 2013 SPD, the Geomorphology Study (Study 6.5) included
the following effort to provide for the potential analysis of the influence of glacial surge on
reservoir sediment accumulation rates in RSP Section 6.5.4.8.2.1 if sediment from glacial surge
can actually be delivered to the reservoir:
Potential additional sediment loading resulting from glacial surge will be investigated in
the Glacier and Runoff Changes Study ([RSP] Section 7.7.4.4, Analyze Potential Changes
in Sediment Delivery to Watana Reservoir). If this investigation indicates that the
increased sediment load can actually be delivered in substantial quantities to Watana
Reservoir, more detailed analyses of the increased loading will be performed and a
sediment loading scenario accounting for glacial surge will be added to the reservoir
trap efficiency and sediment accumulation analysis. This would include an estimate of the
reduction in reservoir life that could result from sediment loading associated with
periodic glacial surges.
As a result of performing this analysis it was concluded that no further geomorphic
investigations were warranted for flow or sediment production from glacial surges (Tetra Tech
2014e). This included a recommendation to not include a glacial surge sediment loading scenario
in the reservoir sediment trap efficiency and sediment accumulation modeling in the reservoir
trap efficiency and sediment accumulation rates task (RSP Section 6.5.4.8.2.1)in Reservoir
Geomorphology study component of the Geomorphology Study (6.5).
7.2. Modifications to Study Plan
The following modifications to the Study Plan beyond those described in Study 6.5 ISR Part C
Section 7.1.2 are proposed to complete the study.
7.2.1. Study Component: Sediment Supply and Transport Middle and Lower
Susitna River Segments
It is proposed that calculation of the effective discharge associated with operation scenarios to be
analyzed not be performed for the Middle River. Due to the supply limited nature of the Middle
River (Tetra Tech 2015b), calculation of effective discharge is not meaningful. In terms of the
Lower River the effective discharge will be determined, but instead of using sediment transport
rating curves, the 1-D bed evolution model sediment transport results will be used to determine
effective discharge. This will be accomplished by placing the sediment transport rates from the
1-D bed evolution model for each time increment into bins of equal water discharge and
determining which discharge interval transports the largest portion of the sediment load . This
will be performed at Sunshine and Susitna Station (represents geomorphic reach LR-5). One
representative cross section in each of the four other Lower River geomorphic reaches
represented in the 1-D bed evolution model (geomorphic reaches LR-1, LR-2, LR-3 and LR-4)
will be used to determine the effective discharge.
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 37 October 2015
7.2.2. Study Component: Reconnaissance-Level Assessment of Project Effects
on Lower and Middle Susitna River Segments
Two Study Plan modifications are proposed for this study component. One addresses the use of
the modified braiding index (MBI) and the other the application of the Grant et al. (2003)
framework for interpreting downstream effects of dams.
In the first modification, it is proposed that determination of the MBI not be performed. Its use
is not applicable to the Middle River segment because the planform does not consist of dynamic
multiple bar-braided channels within a braid plain. The Middle River does have areas with
multiple channels upstream of valley floor constrictions, but these are less dynamic island-
braided channels. The vegetated islands and channels have been very stable over the last 60
years (Tetra Tech 2014c). Results from the 1-D bed evolution model have shown that in the
Lower River, the sediment regime is not substantially altered by the Project (Tetra Tech 2014g
and Tera Tech 2015b). The large inflow of sediment and water at the Three Rivers confluence,
primarily from the Chulitna River, substantially attenuates the alteration in sediment transport
and stream flow that occurs on the Middle River due to the proposed Project. The application of
the MBI, which is an index of braiding potential, in the Lower River will not produce useful
information that would add to the assessment of potential Project impacts beyond what is
proposed in this section with the streamflow assessment, sediment transport assessment and
framework for First-order and Second-order analysis of dam effects on river morphology.
The second proposed modification is to replace the Grant et al. (2003) framework for analyzing
the downstream impact of the Project with the framework for First- and Second-order analysis of
dam effects on river morphology (See Section 5.11 above) that was developed as part of the
Geomorphology Study (6.5) specifically for the conditions on the Susitna River. For example,
the framework in this study recognizes the influence of ice on the morphology of the Susitna
River and includes more parameters that the Project will affect than Grant et al. (2003). The
proposed framework developed in this study will have a higher level of sensitivity to Project
effects and the ability to discern differences between various Project scenarios since it was
specifically designed to utilize a wide range of information that will be provided from the
modeling and analysis efforts conducted in the Fluvial Geomorphology Modeling Study (6.6),
the Riparian Instream Flow Study (8.6) and the Ice Processes Study (7.6). The Grant et al. (2003)
framework provided a useful tool to help with the decision on whether to extend the 1-D bed
evolution model downstream of Sunshine in the Lower River (Tetra Tech 2013c) but does not
have the resolution to ascertain differences between alternative Project scenarios that has been
incorporated into the First- and Second-order Project effects framework developed specifically
as part of the Geomorphology Study (6.5) and that are available from the 1-D model results from
Fluvial Geomorphology Modeling Study (6.6).
7.2.3. Study Component: Reservoir Geomorphology
One modification is proposed for this study component regarding the reservoir tributary delta
formation task. Based on comments at the Initial Study Report (ISR) Meeting held October 16,
2014 in Anchorage, it was decided to develop a 1-D model to determine the depositional
characteristics of the sand and larger sediment fraction of the sediment inflow to the reservoir for
various operations scenarios in the upper end of the reservoir. Previously, the results of the
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 38 October 2015
Environmental Fluid Dynamics Code (EFDC) model from the Water Quality Modeling Study
(5.6) were designated to serve this purpose. The proposed 1-D model will be similar to the 1-D
bed evolution model developed for the Middle and Lower Susitna River segments in the Fluvial
Geomorphology Modeling Study (6.6). The model will extend from just below the downstream
limits of the reservoir fluctuation zone to a distance approximately 5 miles upstream of the
Oshetna River confluence. The upstream limit places the model approximately 8 miles upstream
of the upper limit of the reservoir inundation zone. This effort would require survey of cross
sections in the model domain, collection of bed material samples and measurement of water
surface elevations for model calibration. Data collection needs will be similar to those identified
in Study 6.6 RSP Section 6.6.4.1.2.9.1. The model would be developed and run for the pre-
Project condition as well as the with-Project operations scenarios.
8. LITERATURE CITED
Grant, Gordon E., John C. Schmidt, and Sarah L. Lewis. 2003. A Geological Framework for
Interpreting Downstream Effects of Dams on Rivers. In Water Science and Application
Series Volume 7 A Peculiar River: Geology, Geomorphology, and Hydrology of the
Deschutes River, Oregon, Pg 203-219.
Harrison, W.D. 2012. Personal Communication – teleconference with M.D. Harvey and W.T.
Fullerton, September 10, 2012.
HDR. 2014. White Paper: Review and Compilation of Existing Cold Regions Hydropower
Project Operations Effects. Study 7.6, ISR Part C – Appendix C. Susitna-Watana
Hydroelectric Project FERC Project No. 14241. Prepared for Alaska Energy Authority.
June 2014.
R2 Resource Consultants, Inc. (R2). 2013. Selection of Focus Areas and Study Sites in the
Middle and Lower Susitna River for Instream Flow and Joint Resource Studies- 2013 and
2014, Susitna-Watana Hydroelectric Project FERC Project No. 14241. Prepared for
Alaska Energy Authority. March 1, 2013
R2 Resource Consultants, Inc. and Tetra Tech 2014. Dam Effects on Downstream Channel and
Floodplain Geomorphology and Riparian Plant Communities and Ecosystems – A
Critical Literature Review. Technical Memorandum. November 14, 2014. Susitna-
Watana Hydroelectric Project. Prepared for the Alaska Energy Authority. Anchorage,
Alaska.
Schumm, S.A. 1991. To Interpret the Earth: Ten Ways to be Wrong. Cambridge University
Press, 133 p.
Tetra Tech. 2013a. Development of Sediment Transport Relationships and an Initial Sediment
Balance for the Middle and Lower Susitna River Segments. Susitna-Watana
Hydroelectric Project. 2012 Study Technical Memorandum. Prepared for the Alaska
Energy Authority. Anchorage, Alaska.
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 39 October 2015
Tetra Tech. 2013b. Initial Geomorphic Reach Delineation and Characterization, Middle and
Lower Susitna River Segments. Susitna-Watana Hydroelectric Project. 2012 Study
Technical Memorandum. Prepared for the Alaska Energy Authority. Anchorage, Alaska.
Tetra Tech. 2013c. Reconnaissance Level Assessment of Potential Channel Change in the Lower
Susitna River Segment. Susitna-Watana Hydroelectric Project. 2012 Study Technical
Memorandum. Prepared for the Alaska Energy Authority. Anchorage, Alaska.
Tetra Tech. 2013d. Stream Flow Assessment. Susitna-Watana Hydroelectric Project. 2012 Study
Technical Memorandum. Prepared for the Alaska Energy Authority. Anchorage, Alaska.
Tetra Tech. 2013e. Synthesis of 1980s Aquatic Habitat Information. Susitna-Watana
Hydroelectric Project. 2012 Study Technical Memorandum. Prepared for the Alaska
Energy Authority. Anchorage, Alaska.
Tetra Tech. 2013f. Mapping of Aquatic Macrohabitat Types at Selected Sites in the Middle and
Lower Susitna River Segments from 1980s and 2012 Aerials. Susitna-Watana
Hydroelectric Project. 2012 Study Technical Memorandum. Prepared for the Alaska
Energy Authority. Anchorage, Alaska.
Tetra Tech. 2013g. Mapping of Geomorphic Features and Assessment of Channel Change in the
Middle and Lower Susitna River Segments from 1980s and 2012 Aerials. Susitna-Watana
Hydroelectric Project. 2012 Study Technical Memorandum. Prepared for the Alaska
Energy Authority. Anchorage, Alaska.
Tetra Tech. 2013h. Fluvial Geomorphology Modeling Approach. Draft Technical Memorandum.
Revised June 30, 2013. Susitna-Watana Hydroelectric Project. Prepared for the Alaska
Energy Authority. Anchorage, Alaska.
Tetra Tech. 2013i. Field Assessment of Underwater Camera Pilot Test for Sediment Grain Size
Distribution. Field Report. Review Draft: June 30. Susitna-Watana Hydroelectric Project.
Prepared for the Alaska Energy Authority. Anchorage, Alaska.
Tetra Tech. 2014a. Susitna River Historical Cross Section Comparison. Technical Memorandum.
September 17, 2014. Susitna-Watana Hydroelectric Project. Prepared for the Alaska
Energy Authority. Anchorage, Alaska.
Tetra Tech. 2014b. Update of Sediment-Transport Relationships and a Revised Sediment
Balance for the Middle and Lower Susitna River Segments. Technical Memorandum.
September 17, 2014. Susitna-Watana Hydroelectric Project. Prepared for the Alaska
Energy Authority. Anchorage, Alaska.
Tetra Tech. 2014c. Mapping of Geomorphic Features and Turnover within the Middle and
Lower Susitna River Segments from 1950s, 1980s, and Current Aerials. Technical
Memorandum. September 26, 2014. Susitna-Watana Hydroelectric Project. Prepared for
the Alaska Energy Authority. Anchorage, Alaska.
Tetra Tech. 2014d. Updated Mapping of Aquatic Macrohabitat Types in the Middle Susitna
River Segment from 1980s and Current Aerials. Technical Memorandum. September 26,
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 40 October 2015
2014. Susitna-Watana Hydroelectric Project. Prepared for the Alaska Energy Authority.
Anchorage, Alaska.
Tetra Tech 2014e. Assessment of the Potential for Changes in Sediment Delivery to Watana
Reservoir Due to Glacial Surges. Technical Memorandum. November 14, 2014. Susitna-
Watana Hydroelectric Project. Prepared for the Alaska Energy Authority. Anchorage,
Alaska.
Tetra Tech. 2014f. Geomorphic Reach Delineation and Characterization, Upper, Middle and
Lower Susitna River Segments. Updated Technical Memorandum. 1st Revision May
2014. Susitna-Watana Hydroelectric Project. Prepared for the Alaska Energy Authority.
Anchorage, Alaska.
Tetra Tech. 2014g. Decision Point on Fluvial Geomorphology Modeling of the Susitna River
below PRM 29.9. Technical Memorandum. September 26, 2014. Susitna-Watana
Hydroelectric Project. Prepared for the Alaska Energy Authority. Anchorage, Alaska.
Tetra Tech. 2015a. Geomorphic Reach Delineation and Characterization, Upper, Middle and
Lower Susitna River Segments – 2015 Update. Technical Memorandum. Attachment 1 of
Study 6.5 SIR. Susitna-Watana Hydroelectric Project. Prepared for the Alaska Energy
Authority. Anchorage, Alaska.
Tetra Tech. 2015b. 2014 Fluvial Geomorphology Modeling Model Development, Technical
Memorandum. Attachment 1 of Study 6.6 SIR. Susitna-Watana Hydroelectric Project.
Prepared for the Alaska Energy Authority. Anchorage, Alaska.
Turrin, J.B. 2014. Flow Instabilities of Alaskan Glaciers. PhD Dissertation, University of Utah,
Department of Geography, August.
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 41 October 2015
9. TABLES
Table 5-1: Summary of cumulative data collected as part of the Geomorphology Study (Study 6.5) with URLs to access datasets, notes to find description of data in associated report, and identification if data has previously been submitted and superseded.
Active Data Previously Submitted Data (now superseded)
Data Data Type File name
Location
(URLs in
footnotes)
Folder Nesting
Study 6.5
Study
Component*
Data described
in following
report
File name Location
Geomorphic Reach Breaks ArcGIS Shapefile ISR_6_5_GEO_GeomorphicReaches.shp a N/A 1 Initial Study
Report n/a
Opportunistic Water Quality
Parameter Sampling Word Document SIR_6_5_GEO_SuWa TtGeo 2014 OpportunisticWQ QC3 LWZ 20140309.doc d
DATA AND
SPREADSHEETS
>
OPPORTUNISTIC
WQ
1
Study
Implementation
Report
n/a
Opportunistic Water Quality
Parameter Sampling Photos JPEG SIR_6_5_GEO_SuWa Tt Geo DATA + photo date + photo number d
DATA AND
SPREADSHEETS
>
OPPORTUNISTIC
WQ > PHOTOS
1
Study
Implementation
Report
n/a
Upper River Channel Depth
Estimations Excel Spreadsheet SIR_6_6_FGM_2014_TetraTech_Upper River Cross-Sections QC3 LWZ 20141219.xlsx e
DATASHEETS
AND
SPREADSHEETS
> CROSS-
SECTION DATA
> SUSITNA
1aa
Study
Implementation
Report
n/a
Upper River Approximate Cross-
Sections Shapefile SIR_6_6_FieldData_UR_xsecs.shp e SHAPEFILES 1aa
Study
Implementation
Report
n/a
Bed Load and Suspended-load
measurements at select gage
locations on the Susitna River,
Chulitna River, and Talkeetna
River
Excel Spreadsheet SIR_6_5_GEO_USGS_sediment_data.xlsx d
DATASHEETS
AND
SPREADSHEETS
> BED LOAD
AND
SUSPENDED
SEDIMENT
2
Study
Implementation
Report
n/a
Tributary Aerial Reconnaissance
Videos - 8/30/2014
MP4 Video and LRV
files
Middle River Tributary Videos:
Unnamed Tributary PRM 123 at Oxbow II, Deadhorse Creek (PRM 124.4), 5th of July
Creek (PRM 127.3), Skull Creek (PRM 128.1), Sherman Creek (PRM 134.1), 4th of July
Creek (PRM 134.3), Gold Creek (PRM 140.1), Indian River (PRM 142.1), Unnamed
Tributary PRM 144.0, Jack Long Creek (PRM 148.3), Portage Creek (PRM 152.3),
Cheechako Creek (PRM 155.9), Chinook Creek (PRM 160.5), Devil Creek (PRM 164.8),
Unnamed Tributary PRM 173.8, Unnamed Tributary PRM 174.3, Fog Creek (PRM
179.3), Unnamed Tributary PRM 184.0, Tsusena Creek (PRM 184.6)
Upper River Tributary Videos:
Deadman Creek (PRM 189.4), Watana Creek (PRM 196.9)
d
DATASHEETS
AND
SPREADSHEETS
> TRIBUTARY
AERIAL RECON
> 8-30 RECON
3 (Middle
River)
8 (Upper
River)
Study
Implementation
Report
n/a
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 42 October 2015
Active Data Previously Submitted Data (now superseded)
Data Data Type File name
Location
(URLs in
footnotes)
Folder Nesting
Study 6.5
Study
Component*
Data described
in following
report
File name Location
Tributary Aerial Reconnaissance
Photos - 8/30/2014 JEPG SIR_6_5_GEO_SuWa TtGeo DATA 20140830 + Location + Photo + Photo Number +
QC2 ALS 2014MMDD.jpeg. d
3 (Middle
River)
8 (Upper
River)
Study
Implementation
Report
n/a
Reconnaissance Middle and
Upper Susitna River Tributaries
Notes - 8/30/14
Excel Spreadsheet SIR_6_5_GEO_SuWa_TtGeo_Susitna 8-30-14 Trib Recon Notes – Summary.xlsx d
3 (Middle
River)
8 (Upper
River)
Study
Implementation
Report
n/a
Tributary Aerial Reconnaissance
Videos - 9/28 and 9/29/2014 AVCHD Videos SIR_6_5_GEO_SuWa TtGeo Aerial Recon Video# + camera assigned file number d
DATASHEETS
AND
SPREADSHEETS
> TRIBUTARY
AERIAL RECON
> 9-28 AND 9-
29 RECON
3 (Lower and
Middle
River)
8 (Upper
River)
Study
Implementation
Report
n/a
Tributary Aerial Reconnaissance
Video File Number List and Notes
on Video Location - 9/28 and
9/29/2014
Excel Spreadsheet SIR_6_5_GEO_SuWa TtGeo 9-28 and 9-29-14 Aerial Recon Video Locations.xlsx d
3 (Lower and
Middle
River)
8 (Upper
River)
Study
Implementation
Report
n/a
Tributary Aerial Reconnaissance
Photos - 9/28 and 9/29/2014 JPEG SIR_6_5_GEO_SuWa_TtGeo_Aerial Recon + photo number d
3 (Lower and
Middle
River)
8 (Upper
River)
Study
Implementation
Report
n/a
Aerial Reconnaissance Lower,
Middle, and Upper Susitna River
Tributaries Field Notes - 9/28 and
9/29/2014
PDF SIR_6_5_GEO_9-28-15 and 9-29-15 Recon Fieldnotes DPizzi.pdf d
3 (Lower and
Middle
River)
8 (Upper
River)
Study
Implementation
Report
n/a
1950s Middle River Mapped
Geomorphic Features Shapefile ISR_MTG_6_5_GEO_1950s_MR_GeomFeat.shp b
N/A
4
Mapping of
Geomorphic
Features and
Turnover within
the Middle and
Lower Susitna
River Segments
from 1950s,
1980s, and
Current Aerials
filed with FERC
(Tetra Tech
2014c).
n/a
1950s Lower River Mapped
Geomorphic Features Shapefile ISR_MTG_6_5_GEO_1950s_LR_GeomFeat.shp b 4 n/a
1980s Middle River Mapped
Geomorphic Features Shapefile ISR_MTG_6_5_GEO_1980s_MR_GeomFeat.shp b 4 ISR_6_5_GEO_1980sM_GeoFeAqMHab.shp a
1980s Lower River Mapped
Geomorphic Features Shapefile ISR_MTG_6_5_GEO_1983_LR_GeomFeat.shp b 4 ISR_6_5_GEO_1983_L_GeomFeat.shp a
2012 Middle River Mapped
Geomorphic Features Shapefile ISR_MTG_6_5_GEO_2012_MR_GeomFeat.shp b 4 ISR_6_5_GEO_2012M_GeoFeAqMHab.shp a
2012 Lower River Mapped
Geomorphic Features Shapefile ISR_MTG_6_5_GEO_2012_LR_GeomFeat.shp b 4 ISR_6_5_GEO_2012_L_GeomFeat.shp a
2013 Middle River (Three Rivers
Confluence area) Mapped
Geomorphic Features
Shapefile ISR_MTG_6_5_GEO_2013_MR_3RC_GeomFeat.shp b 4 n/a
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 43 October 2015
Active Data Previously Submitted Data (now superseded)
Data Data Type File name
Location
(URLs in
footnotes)
Folder Nesting
Study 6.5
Study
Component*
Data described
in following
report
File name Location
2013 Lower River (Three Rivers
Confluence area) Mapped
Geomorphic Features
Shapefile ISR_MTG_6_5_GEO_2013_LR_3RC_GeomFeat.shp b 4 n/a
2012 to 2013 Middle River
Channel Erosion in Three Rivers
Confluence Area
Shapefile ISR_MTG_6_5_GEO_2012to2013_MR_ChannelErosion.shp b 4 n/a
2012 to 2013 Lower River
Channel Erosion in Three Rivers
Confluence Area
Shapefile ISR_MTG_6_5_GEO_2012to2013_3RC_ChannelErosion.shp b 4 n/a
Middle River Turnover Shapefile ISR_MTG_6_5_GEO_MR_Turnover.shp b 4 n/a
Lower River Turnover Shapefile ISR_MTG_6_5_GEO_LR_Turnover.shp b 4 n/a
Middle River Geomorphic Feature
Tabulation Excel Spreadsheet ISR_MTG_6.5_GEO_GEOMORPH_MR_TABLES_QC3_MRM_20141013.xlsx b 4 n/a
Lower River Geomorphic Feature
Tabulation Excel Spreadsheet ISR_MTG_6.5_GEO_GEOMORPH_LR_TABLES_QC3_MRM_20141013.xlsx b 4 n/a
Middle and Lower River Turnover
Tabulation Excel Spreadsheet ISR_MTG_6.5_GEO_TURNOVER_QC3_MRM_20141013.xlsx b 4 n/a
1950s Aerial Photography GeoTIFF 1950s USGS Historical Susitna Imagery c
N/A
4 Initial Study
Report n/a
1980s Aerial Photography MrSID and GeoTIFF 1983 Historical Susitna Imagery c 4 Initial Study
Report n/a
2012 Aerial Photography MrSID and GeoTIFF 2012 Susitna Riverflow Geomophology c 4 Initial Study
Report n/a
2013 Aerial Photography MrSID and GeoTIFF 2013 Susitna Riverflow Geomorphology c 4 Initial Study
Report n/a
1980s Middle River Mapped
Aquatic Macrohabitat Shapefile ISR_MTG_6_5_GEO_1980s_MR_AqMHab.shp b
N/A
5 Updated
Mapping of
Aquatic
Macrohabitat
Types in the
Middle Susitna
River segment
from 1980s and
Current Aerials
filed with FERC
( Tetra Tech
2014d).
ISR_6_5_GEO_1980sM_GeoFeAqMHab.shp a
1980s Lower River Mapped
Aquatic Macrohabitat Shapefile ISR_MTG_6_5_GEO_1980s_LR_AqMHab.shp b 5 & 7 ISR_6_5_GEO_1983_Lower_AqMHab.shp a
Current (2012/2013) Middle River
Mapped Aquatic Macrohabitat Shapefile ISR_MTG_6_5_GEO_Current_MR_AqMHab.shp b 5 n/a
2013 Middle River Mapped
Aquatic Macrohabitat Shapefile ISR_MTG_6_5_GEO_2013_MR_AqMHab.shp b 5 ISR_6_5_GEO_2012M_GeoFeAqMHab.shp a
2012 Lower River Mapped
Aquatic Macrohabitat Shapefile ISR_MTG_6_5_GEO_2012_LR_AqMHab.shp b 5 & 7 ISR_6_5_GEO_2012_Lower_AqMHab.shp a
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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FERC Project No. 14241 Page 44 October 2015
Active Data Previously Submitted Data (now superseded)
Data Data Type File name
Location
(URLs in
footnotes)
Folder Nesting
Study 6.5
Study
Component*
Data described
in following
report
File name Location
Middle and Lower River Aquatic
Macrohabitat Tabulation Excel Spreadsheet ISR_MTG_6.5_GEO_AQHAB_TABLES_QC3_MRM_20141013.xlsx b 5 n/a
Streamflow Record Extension for
Selected Streams in the Susitna
River Basin, Alaska (USGS 2012)
PDF Report f N/A 6 Initial Study
Report n/a
Extended and Observed
Streamflow Records for Water
Years 1950–2010 for Selected
Streamgages, Susitna River Basin,
Alaska
Excel Spreadsheet Appendix B f N/A 6 Initial Study
Report n/a
Upper River Tributary Field
Reconnaissance Photos JPEGs
Tributary field photos (divided into subfolders by tributary name):
Deadman Creek (PRM 189.4), Watana Creek (PRM 196.9), Kosina Creek (209.1), Jay
Creek (PRM 211.0), Unnamed Tributary PRM 228.5, Goose Creek (PRM 232.8),
Oshetna River (PRM 235.1)
d DATASHEETS
AND
SPREADSHEETS
> UR TRIB FIELD
RECON
8
Study
Implementation
Report
n/a
Upper River Tributary Field
Reconnaissance Photo Logs PDF
Goose Ck and UNT 228.5 - Photo Log.pdf
Jay Ck - Photo Log.pdf
Oshetna - Notes and Photo Log.pdf
Watana Ck - Notes and Photo Log.pdf
d 8
Study
Implementation
Report
n/a
Cumulative (2013 & 2014) Large
Woody Debris Sample Areas Shapefile ISR_6_5_GEO_All_LWD_SampAreas.shp a
DATA AND
SHAPEFILES >
LARGE WOODY
DEBRIS
9 Initial Study
Report n/a
Cumulative (2013 & 2014) Large
Woody Debris Field Inventory Shapefile SIR_6_5_GEO_All_LWD_Piece_Field.shp d 9
Study
Implementation
Report
ISR_6_5_GEO_2013_LWD_Field.shp a
Cumulative (2013 & 2014) Log
Jam Field Inventory Shapefile SIR_6_5_GEO_All_Log_Jam_Field.shp d 9
Study
Implementation
Report
ISR_6_5_GEO_2013_Log_Jam_Field.shp a
1983 Large Woody Debris Aerial
Photography Inventory Shapefile SIR_6_5_GEO_LWD_1983_Aerials.shp d 9
Study
Implementation
Report
n/a
1983 Log Jam Aerial Photography
Inventory Shapefile SIR_6_5_GEO_LJam_1983_Aerials.shp d 9
Study
Implementation
Report
n/a
2012 Large Woody Debris Aerial
Photography Inventory Shapefile SIR_6_5_GEO_LWD_2012_Aerials.shp d 9
Study
Implementation
Report
n/a
2012 Log Jam Aerial Photography
Inventory Shapefile SIR_6_5_GEO_LJam_2012_Aerials.shp d 9
Study
Implementation
Report
n/a
2013 Large Woody Debris Aerial
Photography Inventory Shapefile SIR_6_5_GEO_LWD_2013_Aerials.shp d 9
Study
Implementation
Report
n/a
2013 Log Jam Aerial Photography
Inventory Shapefile SIR_6_5_GEO_LJam_2013_Aerials.shp d 9
Study
Implementation
Report
n/a
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 45 October 2015
Active Data Previously Submitted Data (now superseded)
Data Data Type File name
Location
(URLs in
footnotes)
Folder Nesting
Study 6.5
Study
Component*
Data described
in following
report
File name Location
Access Corridor Reconnaissance
Locations - Stream Crossings Shapefile SIR_6_5_GEO_SuWa_TtGEO_Access_2014_Recon_Streams.shp d
DATA AND
SHAPEFILES >
ACCESS
CORRIDOR
RECON >
SHAPEFILES
10
Study
Implementation
Report
n/a
Access Corridor Reconnaissance
Locations - Route Shapefile SIR_6_5_GEO_SuWa_TtGEO_Access_2014_Recon_Route.shp d 10
Study
Implementation
Report
n/a
Access Corridor Reconnaissance
Photographs JPEG SIR_6_5_GEO_Access_Recon_Photo Number d
DATA AND
SHAPEFILES >
ACCESS
CORRIDOR
RECON >
PHOTOS
10
Study
Implementation
Report
n/a
Notes:
* Further information about data can be found within referenced report and corresponds to study component listed herein. The study component number corresponds to sections identified in the first decimal position. (i.e. Section X.Y) where X identifies the initial section n umber
and Y identifies the study component.
aa Data collected in collaboration with Study 6.6 therefore posted with Study 6.6 data
Location, a: http://gis.suhydro.org/isr/06-Geomorphology/6.5-Geomorphology/
Location, b: http://gis.suhydro.org/Post_ISR/06-Geomorphology/6.5-Geomorphology/
Location, c: http://gis.suhydro.org/raster-data
Location, d: http://gis.suhydro.org/SIR/06-Geomorphology/6.5-Geomorphology/
Location, e: http://gis.suhydro.org/SIR/06-Geomorphology/6.6-Fluvial_Geomorphology_Modeling/
Location, f: http://pubs.usgs.gov/sir/2012/5210/
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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FERC Project No. 14241 Page 46 October 2015
Table 5.1-1: Total Valley Bottom Area, Non-channel Valley Bottom Area, and Terrace Areas for Middle River geomorphic reaches below Devils Canyon.
Geomorphic
Reach
Total Valley
Bottom Area1
(ac.)
Non-Channel Valley
Bottom Area2
(ac.)
Total Terrace Area3
(ac.)
Terrace Area
as Percent of
the Total
Valley Area
Terrace Area as
Percent of the
Non-Channel
Valley Area
MR-5 810 480 160 20% 34%
MR-6 7,950 4,900 2,660 33% 54%
MR-7 4,000 2,460 1,410 35% 57%
MR-8 5,250 4,480 1,390 27% 31%
MR-84 5,250 4,480 2,550 49% 57%
Notes:
1 Total valley bottom area is the total area within 20 feet vertically of the water elevation present at the time of the 2011 Matanuska-Susitna Borough LiDAR.
2 Non-channel valley bottom area is the land area of the valley bottom. It was determined by removing 2012 delineated geomorphic channel (main channel, side channel, side
sloughs, and upland sloughs) from total valley bottom area.
3 Total terrace area is the summation of land units and the channels within the land units that are approximately between 0 feet to 5 feet above the 100-year water surface elevation
from the Study 6.6 1-D hydraulic model. Total terrace area is approximated from the 1950s delineation in the Middle River Turnover shapefile.
4 Total terrace area summation is calculated with the inclusion of intermediate terrace units (i.e. terrace unit surface heights that are greater than 5 feet above the 100-year water
surface elevation from the Study 6.6 1-D hydraulic model).
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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Table 5.1-2 Area and percentage of dissection and erosion of terrace units in Middle River geomorphic reaches below Devils Canyon.
Geomorphic
Reach
Total Terrace
Area1
(Land Area +
Dissection Area
+ Erosion Area)
(ac)
Land Area2
(ac)
Dissection Area3
(ac)
Erosion Area4
(ac)
Erosion as
Percent of
Terrace Area
Dissection as
Percent of
Terrace Area
Destruction
(Erosion and
Dissection)
as Percent
of Terrace
Area
MR-5 160 140 10 10 8% 3% 11%
MR-6 2,660 2,040 440 170 7% 17% 23%
MR-7 1,410 1,340 40 40 3% 3% 5%
MR-8 1,390 1,320 20 50 4% 2% 5%
Notes:
1 Total terrace area is the summation of land units and the channels within the land units that are approximately between 0 f eet to 5 feet above the 100-year water surface elevation
from the Study 6.6 1-D hydraulic model. Total terrace area is approximated from the 1950s delineation in the Middle River Turnover shapefile (Section 5.4.1).
2 Area of Land within a Terrace Area.
3 Dissection Area is channel area within terrace units plus any erosion within the terrace units since the 1950s determined from the Middle River Turnover Shapefile (Section
5.4.1).
4 Erosion Area since the 1950s was determined from the Middle River Turnover Shapefile (Section 5.4.1).
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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Table 5.1-3 Opportunistic water quality parameters.
Date
Time
Location
(Northing /
Easting) Location Description Photo #s Description
Water Quality
Water
Depth
(ft)
Water
Temp.
(C)
Cond. (µS/cm) Turbidity
(NTU)
Comments
Corr. UnCorr.
8/12/14
3182906.9 N
2102963.5 E
PRM 245.5 – inside of
bed (R) single channel
9443 – view u/s TRB
9444- view d/s TRB
9445 – view down bank
TRB
9446 – view across xsec
TRB - TLB
1 9.92 101 142 162.7
Sample site is d/s
of high erosion site
on glaciolacustrine
near PRM 248
1200
8/12/14 3165795.6 N
2080675.6 E
Oshetna TLB above
confluence w/ Susitna [No photos recorded] 2 11.37 113 153 9.14
1815
8/13/14 3167056.3 N
2071826.8 E
Upstream Goose Ck
confluence – Susitna
MC TLB
9801 – view d/s from
sample site
9802 – view u/s from samp
site
9803 – view up Goose ck
1 9.83 108 152 125.1
1440
8/13/14 3167128.7 N
2071782.6 E Goose Ck TRB
9817 – view d/s fan TRB
9806 – view d/s Goose ck
9807 – view of Goose
confluence
1 10.43 79 57 1.16
Cond. Corrected
reading was with
“C” on measuring
inst. 1455
8/13/14 3185288.9 N
2066896.9 E
Upstream UNT 228.5
confluence – Susitna
MC TRB
1050- view u/s UNT 228.5
1048- view d/s TLB from
conf.
1047 – view u/s UNT 228.5
1.8
9.91
151 107 118.0 “
1610
8/13/14 3185316.1 N
2066802.0 E UNT 228.5 mouth
1050- view u/s UNT 228.5
1048- view d/s TLB from
conf.
1047 – view u/s UNT 228.5
1 9.86 199 141 0.84
1625
8/14/14 3188082.7 N
2033425.7 E
Susitna PRM 221 TRB
u/s trib
1147 –view u/s, people at
sample site 1 8.85 151 105 135.8 1530
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Date
Time
Location
(Northing /
Easting) Location Description Photo #s Description
Water Quality
Water
Depth
(ft)
Water
Temp.
(C)
Cond. (µS/cm) Turbidity
(NTU)
Comments
Corr. UnCorr.
8/14/14 3188191.4 N
2033354.2 E TRIB at PRM 221 1151- view u/s
1152 – view d/s 0.5 7.43 182 121 87.81
1535
8/15/14 3212845.0 N
1993984.9 E Jay Ck 1258 – view u/s at Ck
1257 – view d/s at Ck 1.0 7.39 204 135 2.83
Conducted in
lower most
channel of Jay Ck.
3’ from TLB. 15 ‘
above confluce
with Susitna. 5 cfs
on probe 1040
8/15/14 3212486.9 N
1994607.5 E Susitna R. 1279 – view u/s at site
1280 – view d/s at site 1.3 9.17 150 107 136.1
Conducted 40’
above beginning of
Jay Ck. 6’ from
TRB. 1 cfs on
probe 1100
8/15/14 3214453.2 N
1985341.0 E
Susitna R. u/s Kosina
Ck [No Photos recorded] 1.0 9.19 155 108 125.1
Conducted u/s of
upmost distributary
of Kosina Ck
1215
8/15/14 3214648.2 N
1985046.6 E Kosina Ck
1339, 1342 –view up
Kosina
1343, 1340 – view d/s to
mouth
1.3 10.18 85 61 0.51
Conducted 50’ u/s
of mouth with
Susitna
1220
8/16/14
3230358.7 N
1931795.5 E
Watana Ck
1407 – view u/s Watana
1409 – view d/s to mouth
1.0
7.77
188
126
12.75
Conducted 100’
u/s of mouth with
Susitna. 4’ from
TRB. 2 cfs on
probe 1122
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Date
Time
Location
(Northing /
Easting) Location Description Photo #s Description
Water Quality
Water
Depth
(ft)
Water
Temp.
(C)
Cond. (µS/cm) Turbidity
(NTU)
Comments
Corr. UnCorr.
8/16/14 3230253.5 N
1931948.4 E
Susitna R u/s Watana
Ck
1427 – view u/s on Su TRB
1428 – view d/s on Su TRB
1.8 9.18 150 105 115.8
Conducted u/s 50’
of above Watana
ck. 3’
From TRB. 2 cfs
of probe
1150
8/16/14 3229523.2 N
1895706.3E
Susitna R. u/s
Deadman Ck
504 – view u/s TRB
505 – view d/s TRB 1.5 9.55 148 105 125.6
Conducted 250’
u/s above Dead
man Ck mouth. 3’
from TRB. 1 cfs on
probe
1656
8/16/14 3229389.0 N
1895409.9 E Deadman Ck. 517 – view u/s
520 – view d/s ck. 2.2 11.08 65 48 0.66
Conducted 200’
u/s of confluence
with Susitna. 2’
from TLB. 1 cfs on
Probe
1700
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Table 5.1-4. Upstream and Downstream PRM Boundaries for Geomorphic Assessment Areas Studied in 2013 and 2014.
Geomorphic Assessment
Area
PRM Length Year of Geomorphic
Mapping Downstream Upstream mile
GAA-Whiskers Slough 104.2 107.4 3.2 2013
GAA-Oxbow I 113.6 115.3 1.7 2013
GAA-Slough 6A 115.3 117.3 2.0 2013
GAA-Slough 8A 128.1 130.4 2.3 2013
GAA-Gold Creek 137 140.1 3.1 2013
GAA-Indian River 140.1 143.6 3.5 2013
GAA-Slough 21 143.6 146.1 2.5 2013
GAA-Portage Creek 151.8 152.3 0.5 2014
GAA-Stephan Lake Complex 173.6 175.7 2.1 2014
GAA-Watana Dam 184.7 185.7 1.0 2014
Table 5.2 -1. Dates and Locations of Sediment Transport Data collected by the USGS in 2014.
Sediment
Sample
Type
Susitna
River
above
Tsusena
Creek
Gage no.
15291700
Susitna
River at
Gold
Creek
Gage no.
15292000
Susitna
River near
Talkeetna,
AK Gage
no.
15292100
Chulitna
River near
Talkeetna,
AK Gage
no.
15292400
Talkeetna
River at
Talkeetna,
AK Gage
no.
15292700
Susitna
River at
Sunshine
near
Talkeetna,
AK Gage
no.
15292780
Yentna
River near
Susitna
Station
Gage no.
15294345
Susitna
River near
Susitna
Station
Gage no.
15294350
Suspended
Sediment
5/29/2014,
7/16/2014,
9/10/2014,
9/29/2014
7/30/2014,
8/27/2014
5/12/2014,
5/21/2014,
6/30/2014,
7/30/2014,
9/17/2014
5/8/2014,
5/22/2014,
6/25/2014,
7/29/2014,
8/26/2014,
9/16/2014
5/6/2014,
5/20/2014,
6/24/2014,
6/26/2014,
7/28/2014,
8/25/2014,
9/25/2014
10/22/2013,
5/7/2014,
5/23/2014,
6/23/2014,
7/31/2014,
8/28/2014,
9/30/2014
5/15/2014,
5/28/2014,
8/6/2014,
9/4/2014,
9/15/2014
5/15/2014,
5/27/2014,
5/28/2014,
7/1/2014,
8/6/2014,
9/3/2014
Bedload N/A N/A
5/19/2014,
7/30/2014,
9/17/2014
N/A
5/6/2014,
5/20/2014,
6/24/2014,
7/28/2014,
9/25/2014
5/7/2014,
5/23/2014,
6/23/2014,
7/31/2014,
8/28/2014
5/15/2014,
5/28/2014,
7/2/2014,
8/7/2014,
9/4/2014,
9/15/2014
5/15/2014,
5/28/2014,
7/1/2014,
8/5/2014,
9/3/2014
Bed
Material 9/29/2014 N/A 9/30/2014 10/21/2013 9/25/2014 10/22/2014,
9/30/2014 N/A N/A
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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Table 5.2-2. Summary of Sediment Data Collected by USGS in 2012, 2013, and 2014.
Gage
Number Gage Name Year of
Collection
Discharge
Gage
Station
(Y/N)
Number of Samples Collected
Suspended
Sediment
Bedload
Sediment
Bed
Material
15291700 Susitna R above Tsusena Creek 2012 N 6 5 0
15291700 Susitna R above Tsusena Creek 2013 N 5 1 2
15291700 Susitna R above Tsusena Creek 2014 N 4 0 1
15292000 Susitna River at Gold Creek 2012 Y 0 0 0
15292000 Susitna River at Gold Creek 2013 Y 4 0 0
15292000 Susitna River at Gold Creek 2014 Y 2 0 0
15292100 Susitna River near Talkeetna, AK 2012 N 5 6 0
15292100 Susitna River near Talkeetna, AK 2013 N 5 4 1
15292100 Susitna River near Talkeetna, AK 2014 N 5 3 1
15292400 Chulitna River near Talkeetna, AK 2012 N 3 0 0
15292400 Chulitna River near Talkeetna, AK 2013 N 5 0 0
15292400 Chulitna River near Talkeetna, AK 2014 N 6 0 1
15292410 Chulitna River below Canyon near Talkeetna, AK 2012 N 5 4 0
15292410 Chulitna River below Canyon near Talkeetna, AK 2013 N 1 4 0
15292410 Chulitna River below Canyon near Talkeetna, AK 2014 N 0 6 0
15292700 Talkeetna River at Talkeetna, AK 2012 Y 0 0 0
15292700 Talkeetna River at Talkeetna, AK 2013 Y 8 5 1
15292700 Talkeetna River at Talkeetna, AK 2014 Y 7 5 1
15292780 Susitna River at Sunshine near Talkeetna, AK 2012 Y 9 6 0
15292780 Susitna River at Sunshine near Talkeetna, AK 2013 Y 5 4 0
15292780 Susitna River at Sunshine near Talkeetna, AK 2014 Y 7 5 2
15294345 Yentna River near Susitna Station 2012 N 0 0 0
15294345 Yentna River near Susitna Station 2013 N 5 4 0
15294345 Yentna River near Susitna Station 2014 N 5 6 0
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Gage
Number Gage Name Year of
Collection
Discharge
Gage
Station
(Y/N)
Number of Samples Collected
Suspended
Sediment
Bedload
Sediment
Bed
Material
15294350 Susitna River at Susitna Station 2012 Y 0 0 0
15294350 Susitna River at Susitna Station 2013 Y 5 4 0
15294350 Susitna River at Susitna Station 2014 Y 6 5 0
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Table 5.2-3. USGS Suspended Sediment Transport Data Collected in 2012, 2013, and 2014.
Gage
Number Gage Name Date of
Collection
Time of
Collection
Discharge
Suspended
Sediment
Concentration
Suspended
Sediment
Discharge,
Qs
Suspended Sediment Percent finer than size indicated, in millimeters
Silt
and
Clay
Sand
Sediment
Discharge,
Qs,
Silt and
Clay
Sediment
Discharge,
Qs,
Sand
(cfs) (mg/L) (tons/day) 0.001 0.002 0.004 0.008 0.016 0.031 0.0625 0.125 0.25 0.5 1 2 4 % % (tons/day) (tons/day)
15291700 Susitna River above Tsusena Creek 4/10/2012 13:50 1,090 3 9 54 54 46 5 4
15291700 Susitna River above Tsusena Creek 5/10/2012 15:20 8,610 321 7,460 0 8 13 19 27 38 47 62 83 97 100 100 100 47 53 3,506 3,954
15291700 Susitna River above Tsusena Creek 6/3/2012 13:00 14,200 151 5,790 0 0 0 0 0 0 21 28 48 91 99 100 100 21 79 1,216 4,574
15291700 Susitna River above Tsusena Creek 7/2/2012 19:00 20,600 283 15,700 13 19 26 35 46 57 62 69 78 95 100 100 100 62 38 9,734 5,966
15291700 Susitna River above Tsusena Creek 8/7/2012 11:10 14,000 184 6,960 10 16 24 33 42 50 55 62 73 94 100 100 100 55 45 3,828 3,132
15291700 Susitna River above Tsusena Creek 9/14/2012 10:30 8,170 44 971 35 46 67 91 99 100 100 35 65 340 631
15291700 Susitna River above Tsusena Creek 6/21/2013 10:50 25,400 799 54,800 27 39 52 64 74 80 83 88 93 98 99 99 100 83 17 45,484 9,316
15291700 Susitna River above Tsusena Creek 7/25/2013 10:40 17,400 766 36,000 81 85 91 98 100 100 100 81 19 29,160 6,840
15291700 Susitna River above Tsusena Creek 8/5/2013 17:10 14,900 637 25,600 24 32 44 59 71 78 83 86 92 99 100 100 100 83 18 21,128 4,473
15291700 Susitna River above Tsusena Creek 9/3/2013 18:30 18,200 312 15,300 39 51 67 92 99 100 100 39 61 5,967 9,333
15291700 Susitna River above Tsusena Creek 9/23/2013 17:50 7,810 70 1,480 39 51 69 92 100 100 100 39 61 577 903
15291700 Susitna River above Tsusena Creek 5/29/2014 17:55 10,500 140 3,970 25 32 48 91 100 100 100 25 76 955 3,015
15291700 Susitna River above Tsusena Creek 7/16/2014 18:35 22,200 363 21,750 13 26 38 45 50 55 58 63 72 93 100 100 100 58 43 12,506 9,245
15291700 Susitna River above Tsusena Creek 9/10/2014 18:35 13,100 73 2,565 19 25 41 81 96 100 100 19 82 473 2,092
15291700 Susitna River above Tsusena Creek 9/29/2014 15:35 8,500 36 826 33 42 62 95 100 100 100 33 68 268 558
15292000 Susitna River at Gold Creek 3/27/2013 16:10 1,510 498 26,900 44 44 56 2 2
15292000 Susitna River at Gold Creek 6/6/2013 14:30 41,700 375 30,500 54 54 46 33,696 28,704
15292000 Susitna River at Gold Creek 8/15/2013 15:40 19,300 334 25,200 80 86 93 99 100 100 100 80 20 25,120 6,280
15292000 Susitna River at Gold Creek 9/26/2013 14:30 11,500 227 10,800 60 75 87 96 100 100 100 60 40 373 248
15292000 Susitna River at Gold Creek 7/30/2014 17:10 19,900 412 22,100 91 93 96 99 100 100 100 91 9 20,111 1,989
15292000 Susitna River at Gold Creek 8/27/2014 15:20 19,000 129 6,620 46 54 70 94 100 100 100 46 54 3,045 3,575
15292100 Chulitna River near Talkeetna, AK 5/17/2012 14:30 7,940 244 5,230 56 56 44 2,929 2,301
15292100 Susitna River near Talkeetna, AK 5/23/2012 12:10 20,000 498 26,900 0 6 10 14 22 33 43 61 79 98 100 100 100 43 57 11,567 15,333
15292100 Susitna River near Talkeetna, AK 6/5/2012 11:30 30,100 375 30,500 0 6 10 13 18 26 34 50 80 99 100 100 100 34 66 10,370 20,130
15292100 Susitna River near Talkeetna, AK 7/10/2012 13:50 27,900 334 25,200 14 20 29 42 56 67 71 77 87 99 100 100 100 71 29 17,892 7,308
15292100 Susitna River near Talkeetna, AK 8/14/2012 16:50 17,700 227 10,800 29 40 52 65 77 84 87 91 94 99 100 100 100 87 13 9,396 1,404
15292100 Susitna River near Talkeetna, AK 9/25/2012 14:20 43,700 857 101,000 23 29 37 45 54 63 67 78 93 99 100 100 100 67 33 67,670 33,330
15292100 Susitna River near Talkeetna, AK 6/4/2013 17:36 54,400 905 133,000 13 17 22 28 36 45 53 69 90 99 100 100 100 53 47 70,490 62,510
15292100 Susitna River near Talkeetna, AK 7/10/2013 20:00 22,400 334 20,200 18 31 42 56 70 78 83 90 96 100 100 100 100 83 17 16,766 3,434
15292100 Susitna River near Talkeetna, AK 8/13/2013 19:30 17,700 528 25,200 23 36 48 62 75 86 91 95 98 100 100 100 100 91 9 22,932 2,268
15292100 Susitna River near Talkeetna, AK 9/5/2013 12:40 32,200 417 36,300 52 65 86 99 100 100 100 52 48 18,876 17,424
15292100 Susitna River near Talkeetna, AK 9/25/2013 12:40 11,300 20 610 67 78 90 100 100 100 100 67 33 409 201
15292100 Susitna River near Talkeetna, AK 5/12/2014 21:25 22,000 469 27,850 17 21 26 33 42 54 63 75 90 99 100 100 100 63 38 17,407 10,444
15292100 Susitna River near Talkeetna, AK 5/21/2014 19:00 14,200 63 2,420 48 62 81 98 100 100 100 48 52 1,170 1,250
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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FERC Project No. 14241 Page 55 October 2015
Gage
Number Gage Name Date of
Collection
Time of
Collection
Discharge
Suspended
Sediment
Concentration
Suspended
Sediment
Discharge,
Qs
Suspended Sediment Percent finer than size indicated, in millimeters
Silt
and
Clay
Sand
Sediment
Discharge,
Qs,
Silt and
Clay
Sediment
Discharge,
Qs,
Sand
(cfs) (mg/L) (tons/day) 0.001 0.002 0.004 0.008 0.016 0.031 0.0625 0.125 0.25 0.5 1 2 4 % % (tons/day) (tons/day)
15292100 Susitna River near Talkeetna, AK 6/30/2014 19:50 28,700 252 19,500 25 25 75 4,863 14,637
15292100 Susitna River near Talkeetna, AK 7/30/2014 13:35 19,500 140 7,345 20 38 49 56 61 66 68 75 85 99 100 100 100 68 32 4,997 2,348
15292100 Susitna River near Talkeetna, AK 9/17/2014 12:05 22,100 274 16,350 37 49 57 65 71 76 79 84 92 99 100 100 100 79 22 12,827 3,524
15292400 Chulitna River near Talkeetna, AK 6/7/2012 16:20 19,700 1120 59,600 62 62 38 36,952 22,648
15292400 Chulitna River near Talkeetna, AK 9/19/2012 17:40 34,500 1510 141,000 53 53 47 74,730 66,270
15292400 Chulitna River near Talkeetna, AK 1/23/2013 15:00 1,490 9 36 70 70 30 25 11
15292400 Chulitna River near Talkeetna, AK 3/26/2013 16:30 980 5 13 42 42 58 6 8
15292400 Chulitna River near Talkeetna, AK 6/5/2013 15:25 23,350 880 55,500 31 41 52 62 68 71 79 82 90 98 100 100 100 79 22 43,572 11,928
15292400 Chulitna River near Talkeetna, AK 7/12/2013 19:00 23,700 1,720 110,000 21 29 41 54 66 77 82 91 97 100 100 100 100 82 18 90,200 19,800
15292400 Chulitna River near Talkeetna, AK 8/14/2013 15:10 24,700 1,590 106,000 23 32 57 67 74 78 84 91 98 100 100 100 78 22 82,680 23,320
15292400 Chulitna River near Talkeetna, AK 5/8/2014 14:45 11,700 248 7,533 17 22 30 38 45 50 55 63 75 93 99 55 46 4,068 3,465
15292400 Chulitna River near Talkeetna, AK 5/22/2014 14:12 11,700 461 14,567 22 29 39 48 55 60 62 68 79 96 100 100 100 62 38 9,031 5,535
15292400 Chulitna River near Talkeetna, AK 6/25/2014 18:15 20,900 498 22,300 65 65 36 14,422 7,879
15292400 Chulitna River near Talkeetna, AK 7/29/2014 13:25 21,700 562 31,950 19 26 37 46 54 60 64 72 82 96 100 100 100 64 36 20,346 11,604
15292400 Chulitna River near Talkeetna, AK 8/26/2014 15:25 16,900 595 31,700 27 32 42 50 58 63 66 72 81 94 100 100 100 66 35 20,471 11,229
15292400 Chulitna River near Talkeetna, AK 9/16/2014 15:45 20,700 1,520 82,100 42 56 70 78 83 86 88 91 95 99 100 100 100 88 13 71,543 10,557
15292410 Chulitna R bel. Canyon near Talkeetna, AK 5/17/2012 11:20 7,950 244 5,240 0 15 23 31 41 52 59 74 92 100 100 100 100 59 41 3,092 2,148
15292410 Chulitna R bel. Canyon near Talkeetna, AK 6/7/2012 13:50 19,800 940 50,300 0 29 41 52 61 66 70 81 91 98 100 100 100 70 30 35,210 15,090
15292410 Chulitna R bel. Canyon near Talkeetna, AK 7/11/2012 12:45 15,800 416 17,700 28 37 48 60 68 74 78 84 92 98 100 100 100 78 22 13,806 3,894
15292410 Chulitna R bel. Canyon near Talkeetna, AK 8/23/2012 16:55 15,600 452 19,000 26 33 42 51 61 69 74 80 90 99 100 100 100 74 26 14,060 4,940
15292410 Chulitna R bel. Canyon near Talkeetna, AK 9/19/2012 14:30 33,600 944 85,600 8 14 21 30 37 46 52 65 81 96 99 100 100 52 48 44,512 41,088
15292410 Chulitna R. bel. Canyon near Talkeetna, AK 9/10/2013 15:30 29,700 850 68,200 15 23 33 43 53 60 66 77 89 98 100 100 100 66 34 45,012 23,188
15292699 Talkeetna River at Talkeetna, AK 5/6/2014 18:00 6,700 292 5,285 28 29 31 32 36 40 26 47 74 95 100 100 100 19 82 978 4,307
15292700 Talkeetna River at Talkeetna, AK 10/16/2012 16:40 5,820 104 1,630 27 27 73 440 1,190
15292700 Talkeetna River at Talkeetna, AK 3/25/2013 17:00 470 3 4 65 65 35 2 1
15292700 Talkeetna River at Talkeetna, AK 5/8/2013 11:30 830 20 45 63 63 37 28 17
15292700 Talkeetna River at Talkeetna, AK 5/31/2013 14:40 25,400 1,560 107,000 51 51 49 54,570 52,430
15292700 Talkeetna River at Talkeetna, AK 7/10/2013 16:00 6,420 298 5,170 52 70 86 99 100 100 100 52 48 2,688 2,482
15292700 Talkeetna River at Talkeetna, AK 8/13/2013 12:00 8,130 1,280 28,100 9 1 19 27 36 45 52 71 90 98 100 100 100 52 48 14,612 13,488
15292700 Talkeetna River at Talkeetna, AK 9/5/2013 19:30 14,400 488 19,000 26 43 77 98 100 100 100 26 74 4,940 14,060
15292700 Talkeetna River at Talkeetna, AK 9/25/2013 17:50 5,240 104 1,470 31 54 82 99 100 100 100 31 69 456 1,014
15292700 Talkeetna River at Talkeetna, AK 5/20/2014 15:15 6,210 99 1,660 20 39 75 98 100 100 100 20 81 324 1,336
15292700 Talkeetna River at Talkeetna, AK 6/24/2014 15:35 9,160 189 4,675 36 36 64 1,683 2,992
15292700 Talkeetna River at Talkeetna, AK 6/26/2014 12:05 20,000 1,845 99,650 53 53 48 52,316 47,334
15292700 Talkeetna River at Talkeetna, AK 7/28/2014 17:55 6,790 342 6,260 4 15 27 31 37 42 46 53 70 96 100 100 100 46 55 2,848 3,412
15292700 Talkeetna River at Talkeetna, AK 8/25/2014 18:25 6,490 365 6,400 17 29 34 40 45 49 56 64 79 96 100 100 100 56 44 3,584 2,816
15292700 Talkeetna River at Talkeetna, AK 9/25/2014 14:15 5,590 67 1,003 22 37 68 98 100 100 100 22 79 216 787
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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FERC Project No. 14241 Page 56 October 2015
Gage
Number Gage Name Date of
Collection
Time of
Collection
Discharge
Suspended
Sediment
Concentration
Suspended
Sediment
Discharge,
Qs
Suspended Sediment Percent finer than size indicated, in millimeters
Silt
and
Clay
Sand
Sediment
Discharge,
Qs,
Silt and
Clay
Sediment
Discharge,
Qs,
Sand
(cfs) (mg/L) (tons/day) 0.001 0.002 0.004 0.008 0.016 0.031 0.0625 0.125 0.25 0.5 1 2 4 % % (tons/day) (tons/day)
15292780 Susitna River at Sunshine nr. Talkeetna, AK 10/6/2011 16:10 13,700 25 925 60 60 40 555 370
15292780 Susitna River at Sunshine nr. Talkeetna, AK 1/31/2012 17:10 3,580 8 77 26 26 74 20 57
15292780 Susitna River at Sunshine nr. Talkeetna, AK 3/19/2012 19:30 2,510 4 27 63 63 37 17 10
15292780 Susitna River at Sunshine nr. Talkeetna, AK 5/22/2012 16:40 35,100 421 39,900 0 9 14 19 27 37 46 62 81 98 100 100 100 46 54 18,354 21,546
15292780 Susitna River at Sunshine nr. Talkeetna, AK 6/5/2012 20:30 63,000 549 93,400 0 13 19 26 33 42 47 63 81 95 100 100 100 47 53 43,898 49,502
15292780 Susitna River at Sunshine nr. Talkeetna, AK 7/10/2012 18:30 53,900 383 55,700 17 25 35 46 57 63 66 74 88 99 100 100 100 66 34 36,762 18,938
15292780 Susitna River at Sunshine nr. Talkeetna, AK 8/13/2012 18:30 43,400 483 56,600 30 39 52 64 75 82 84 90 95 100 100 100 100 84 16 47,544 9,056
15292780 Susitna River at Sunshine nr. Talkeetna, AK 9/17/2012 17:30 69,200 823 154,000 11 19 28 38 47 54 58 74 91 99 100 100 100 58 42 89,320 64,680
15292780 Susitna River at Sunshine nr. Talkeetna, AK 9/22/2012 14:30 154,000 1680 699,000 16 23 31 40 52 63 68 83 96 99 100 100 100 68 32 475,320 223,680
15292780 Susitna River at Sunshine nr. Talkeetna, AK 9/22/2012 15:30 154,000 1680 699,000 0 23 31 40 52 63 68 83 96 99 100 100 100 68 32 475,320 223,680
15292780 Susitna River at Sunshine nr. Talkeetna, AK 3/25/2013 18:20 3,480 2 19 49 49 51 9 10
15292780 Susitna River at Sunshine nr. Talkeetna, AK 6/3/2013 18:25 115,000 1,002 311,000 13 19 26 36 45 54 60 73 90 99 100 100 100 60 41 185,015 125,985
15292780 Susitna River at Sunshine nr. Talkeetna, AK 7/11/2013 18:20 48,100 543 70,500 22 33 46 61 72 79 82 87 92 99 100 100 100 82 18 57,810 12,690
15292780 Susitna River at Sunshine nr. Talkeetna, AK 8/12/2013 15:50 49,700 783 105,000 19 30 40 52 63 73 79 89 96 99 100 100 100 79 21 82,950 22,050
15292780 Susitna River at Sunshine nr. Talkeetna, AK 9/6/2013 14:33 84,000 1,023 232,000 15 21 29 38 47 57 60 75 90 99 100 100 100 60 40 139,065 92,935
15292780 Susitna River at Sunshine nr. Talkeetna, AK 10/22/2013 12:30 29,600 125 9,990 42 52 70 93 99 100 100 42 58 4,196 5,794
15292780 Susitna River at Sunshine nr. Talkeetna, AK 5/7/2014 15:45 45,100 548 66,700 14 19 24 31 37 44 52 64 82 99 100 100 100 52 48 34,684 32,016
15292780 Susitna River at Sunshine nr. Talkeetna, AK 5/23/2014 13:05 29,000 291 22,767 34 40 46 51 56 58 61 66 80 98 100 100 100 61 39 13,998 8,768
15292780 Susitna River at Sunshine nr. Talkeetna, AK 6/23/2014 17:55 55,900 409 61,650 60 60 40 36,990 24,660
15292780 Susitna River at Sunshine nr. Talkeetna, AK 7/31/2014 14:05 48,600 497 65,250 22 30 42 53 63 70 75 82 91 100 100 100 100 75 26 48,610 16,640
15292780 Susitna River at Sunshine nr. Talkeetna, AK 8/28/2014 13:35 48,050 451 58,450 18 25 35 44 53 61 66 75 87 99 100 100 100 66 35 38,274 20,177
15292780 Susitna River at Sunshine nr. Talkeetna, AK 9/30/2014 15:25 24,000 172 11,150 70 75 86 100 100 100 100 70 31 7,773 3,377
15294345 Yentna River near Susitna Station 5/30/2013 18:30 68,500 988 183,000 15 21 28 38 48 57 61 76 90 99 100 100 100 61 39 111,630 71,370
15294345 Yentna River near Susitna Station 6/12/2013 15:10 60,500 830 136,000 24 32 39 47 54 60 63 73 88 99 100 100 100 63 37 85,680 50,320
15294345 Yentna River near Susitna Station 7/8/2013 18:30 58,500 788 124,000 19 26 36 48 58 68 73 83 93 99 100 100 100 73 27 90,520 33,480
15294345 Yentna River near Susitna Station 8/20/2013 13:45 46,500 896 112,000 15 23 32 42 50 56 61 69 80 94 99 100 100 61 39 68,320 43,680
15294345 Yentna River near Susitna Station 9/11/2013 17:40 80,100 972 210,000 12 17 24 33 44 56 63 78 93 100 100 100 100 63 37 132,300 77,700
15294345 Yentna River near Susitna Station 5/15/2014 10:15 32,200 537 46,650 17 20 25 30 37 41 47 56 85 99 100 100 100 47 54 21,677 24,973
15294345 Yentna River near Susitna Station 5/28/2014 12:20 33,350 437 39,300 18 22 27 32 38 42 47 58 82 99 100 100 100 47 53 18,495 20,805
15294345 Yentna River near Susitna Station 8/6/2014 15:10 39,950 470 50,700 25 32 42 52 60 65 69 76 88 99 100 100 100 69 32 34,727 15,973
15294345 Yentna River near Susitna Station 9/4/2014 10:30 24,900 362 24,300 14 22 30 39 47 53 58 69 87 99 100 100 100 58 42 14,094 10,206
15294345 Yentna River near Susitna Station 9/15/2014 16:05 64,950 2,170 380,500 26 37 50 64 74 81 84 91 97 100 100 100 100 84 16 319,655 60,845
15294350 Susitna River at Susitna Station 5/30/2013 14:50 194,000 1,850 967,000 12 17 22 28 34 41 47 65 84 99 100 100 100 47 53 454,490 512,510
15294350 Susitna River at Susitna Station 6/13/2013 14:35 138,000 644 240,000 25 33 43 53 61 66 69 78 96 100 100 100 100 69 31 165,600 74,400
15294350 Susitna River at Susitna Station 7/9/2013 19:50 100,000 581 156,688 17 25 34 43 50 55 58 68 89 100 100 100 100 58 42 90,879 65,809
15294350 Susitna River at Susitna Station 8/19/2013 18:25 89,700 806 195,000 20 30 43 58 71 79 83 88 95 100 100 100 100 83 17 161,850 33,150
15294350 Susitna River at Susitna Station 9/12/2013 16:45 177,000 846 404,000 10 16 23 32 42 54 62 75 91 99 100 100 100 62 38 250,480 153,520
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 57 October 2015
Gage
Number Gage Name Date of
Collection
Time of
Collection
Discharge
Suspended
Sediment
Concentration
Suspended
Sediment
Discharge,
Qs
Suspended Sediment Percent finer than size indicated, in millimeters
Silt
and
Clay
Sand
Sediment
Discharge,
Qs,
Silt and
Clay
Sediment
Discharge,
Qs,
Sand
(cfs) (mg/L) (tons/day) 0.001 0.002 0.004 0.008 0.016 0.031 0.0625 0.125 0.25 0.5 1 2 4 % % (tons/day) (tons/day)
15294350 Susitna River at Susitna Station 5/15/2014 19:50 79,000 361 76,900 17 24 29 35 41 46 50 59 79 99 100 100 100 50 51 37,936 38,964
15294350 Susitna River at Susitna Station 5/27/2014 19:15 59,800 293 47,300 20 26 17 38 43 46 50 60 80 99 100 100 100 50 50 23,666 23,634
15294350 Susitna River at Susitna Station 5/28/2014 18:15 69,300 390 72,967 12 19 26 32 38 44 49 59 80 99 100 100 100 49 51 35,724 37,243
15294350 Susitna River at Susitna Station 7/1/2014 16:10 134,000 559 202,500 66 66 34 133,650 68,850
15294350 Susitna River at Susitna Station 8/6/2014 11:10 90,950 465 114,000 22 29 39 49 57 62 65 71 86 99 100 100 100 65 36 73,500 40,500
15294350 Susitna River at Susitna Station 9/3/2014 15:30 65,100 321 56,400 21 25 32 39 45 51 55 67 88 99 100 100 100 55 45 31,020 25,380
STUDY IMPLEMENTATION REPORT GEOMORPHOLOGY STUDY (STUDY 6.5)
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FERC Project No. 14241 Page 58 October 2015
Table 5.2-4. USGS Bed Load Sediment Transport Data Collected in 2012, 2013, and 2014.
Gage
Number Gage Name Date of
Collection
Time of
Collection
Discharge Bedload Sediment
Discharge, Qs
Bedload Sediment,
Percent finer than size indicated, in millimeters Sand Gravel Sediment Discharge,
Qs, Sand
Sediment Discharge,
Qs, Gravel
(cfs) (tons/day) 0.0625 0.125 0.25 0.5 1 2 4 8 16 31.5 63 128 % % (tons/day) (tons/day)
15291700 Susitna R above Tsusena Creek 5/10/2012 14:40 9,140 142 0 0 1 57 81 90 93 95 98 100 100 100 90 10 128 14
15291700 Susitna R above Tsusena Creek 6/3/2012 11:00 13,700 900 0 0 1 40 70 79 83 87 92 94 100 100 79 21 711 189
15291700 Susitna R above Tsusena Creek 6/3/2012 11:50 13,700 658 0 0 1 45 83 93 96 98 99 100 100 100 93 7 612 46
15291700 Susitna R above Tsusena Creek 7/2/2012 17:10 20,600 488 0 0 0 45 79 89 94 97 99 100 100 100 89 11 434 54
15291700 Susitna R above Tsusena Creek 7/2/2012 18:00 20,600 601 0 0 0 35 60 67 70 74 82 93 100 100 67 33 403 198
15291700 Susitna R above Tsusena Creek 8/6/2012 18:30 16,000 328 0 0 0 48 82 92 95 98 100 100 100 100 92 8 302 26
15291700 Susitna R above Tsusena Creek 8/6/2012 19:00 16,000 307 0 0 1 52 86 94 96 97 98 100 100 100 94 6 289 18
15291700 Susitna R above Tsusena Creek 9/13/2012 16:50 7,650 31 0 0 0 44 78 91 94 96 96 100 100 100 91 9 28 3
15291700 Susitna R above Tsusena Creek 9/13/2012 17:30 7,650 13 0 0 0 55 89 97 99 100 100 100 100 100 97 3 13 0.4
15291700 Susitna R above Tsusena Creek 10/11/2012 15:50 12,200 74 0 0 1 73 92 95 96 97 97 100 95 5 70 4
15291700 Susitna R above Tsusena Creek 10/11/2012 16:20 12,100 126 0 0 1 54 80 90 94 96 99 100 90 10 113 13
15292100 Susitna River near Talkeetna, AK 5/23/2012 12:30 20,000 694 0 0 0 7 8 9 9 9 14 55 100 100 9 91 62 632
15292100 Susitna River near Talkeetna, AK 6/5/2012 13:30 30,100 852 0 1 1 53 71 74 76 77 79 86 100 100 74 26 630 222
15292100 Susitna River near Talkeetna, AK 7/10/2012 14:50 27,900 312 0 0 1 72 92 95 96 98 100 100 100 100 95 5 296 16
15292100 Susitna River near Talkeetna, AK 7/10/2012 15:30 27,700 290 0 0 1 74 94 96 96 98 100 100 100 100 96 4 278 12
15292100 Susitna River near Talkeetna, AK 8/14/2012 15:50 17,700 39 0 1 1 66 80 81 83 87 100 100 100 100 81 19 32 7
15292100 Susitna River near Talkeetna, AK 8/14/2012 16:20 17,700 18 0 0 2 78 98 99 99 100 100 100 100 100 99 1 18 0.2
15292100 Susitna River near Talkeetna, AK 8/24/2012 10:30 16,000 119 0 0 1 61 88 94 98 100 100 100 100 100 94 6 112 7
15292100 Susitna River near Talkeetna, AK 8/24/2012 11:05 16,000 56 0 0 0 76 98 99 100 100 100 100 100 100 99 1 55 1
15292100 Susitna River near Talkeetna, AK 9/25/2012 12:20 43,700 52 0 2 4 79 87 88 88 90 95 100 100 100 88 12 46 6
15292100 Susitna River near Talkeetna, AK 9/25/2012 13:10 43,700 347 0 1 18 59 68 71 73 79 89 100 100 100 71 29 246 101
15292100 Susitna River near Talkeetna, AK 7/10/2013 18:50 22,400 12 0 1 1 79 96 99 100 100 100 100 100 100 99 1 12 0.1
15292100 Susitna River near Talkeetna, AK 8/13/2013 17:50 17,700 32 0 0 1 80 98 99 100 100 100 100 100 100 99 1 32 0.3
15292100 Susitna River near Talkeetna, AK 8/13/2013 18:35 17,700 52 0 0 1 79 96 98 99 100 100 100 100 100 98 2 51 1
15292100 Susitna River near Talkeetna, AK 9/5/2013 14:00 32,200 107 0 0 11 51 66 70 72 74 77 77 100 100 70 30 75 32
15292100 Susitna River near Talkeetna, AK 9/5/2013 14:50 32,200 324 0 0 2 58 76 80 82 85 89 92 100 100 80 20 259 65
15292100 Susitna River near Talkeetna, AK 9/25/2013 13:40 11,300 4 0 1 4 89 99 100 100 100 100 100 100 100 100 0 4 0.0
15292100 Susitna River near Talkeetna, AK 9/25/2013 14:20 11,300 6 0 1 2 81 98 100 100 100 100 100 100 100 100 0 6 0.0
15292100 Susitna River near Talkeetna, AK 5/19/2014 21:15 19,600 110 0 0 0 80 99 100 100 100 100 100 100 100 100 0 110 0.0
15292100 Susitna River near Talkeetna, AK 5/19/2014 21:30 19,600 169 0 0 1 78 98 99 100 99 1 167 2
15292100 Susitna River near Talkeetna, AK 7/30/2014 12:27 19,500 89 0 0 2 69 86 88 89 92 96 88 12 78 11
15292100 Susitna River near Talkeetna, AK 9/17/2014 11:05 22,100 109 0 0 0 9 65 68 69 69 70 68 32 74 35
15292410 Chulitna R Below Canyon near Talkeetna, AK 6/7/2012 12:12 19,800 836 0 0 2 38 67 73 77 82 87 96 100 100 73 27 610 226
15292410 Chulitna R Below Canyon near Talkeetna, AK 7/11/2012 15:10 15,800 1,940 0 0 1 29 52 58 60 63 70 0 100 100 58 42 1,125 815
15292410 Chulitna R Below Canyon near Talkeetna, AK 7/11/2012 16:20 15,800 1,380 0 0 1 25 53 62 66 69 75 92 100 100 62 38 856 524
15292410 Chulitna R Below Canyon near Talkeetna, AK 8/23/2012 15:05 15,600 1,120 0 0 0 13 21 26 36 57 83 0 100 100 26 74 291 829
15292410 Chulitna R Below Canyon near Talkeetna, AK 8/23/2012 15:35 15,600 1,510 0 0 1 15 26 28 36 56 83 95 100 100 28 72 423 1,087
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FERC Project No. 14241 Page 59 October 2015
Gage
Number Gage Name Date of
Collection
Time of
Collection
Discharge Bedload Sediment
Discharge, Qs
Bedload Sediment,
Percent finer than size indicated, in millimeters Sand Gravel Sediment Discharge,
Qs, Sand
Sediment Discharge,
Qs, Gravel
(cfs) (tons/day) 0.0625 0.125 0.25 0.5 1 2 4 8 16 31.5 63 128 % % (tons/day) (tons/day)
15292410 Chulitna R Below Canyon near Talkeetna, AK 9/19/2012 12:30 33,600 3,700 0 0 1 11 20 24 33 54 75 94 100 100 24 76 888 2,812
15292410 Chulitna R Below Canyon near Talkeetna, AK 9/19/2012 13:20 33,600 7,750 0 0 1 8 15 18 29 47 70 91 100 100 18 82 1,395 6,355
15292410 Chulitna River below Canyon near Talkeetna, AK 6/5/2013 11:20 23,600 812 0 0 2 14 26 32 40 55 75 95 100 100 32 68 260 552
15292410 Chulitna River below Canyon near Talkeetna, AK 6/5/2013 12:20 23,600 1,180 0 0 3 15 30 43 53 63 75 90 100 100 43 57 507 673
15292410 Chulitna River below Canyon near Talkeetna, AK 7/12/2013 15:03 23,500 996 0 0 1 20 37 46 50 55 63 79 100 100 46 54 458 538
15292410 Chulitna River below Canyon near Talkeetna, AK 7/12/2013 15:50 23,500 2,150 0 0 1 26 46 52 56 60 68 84 100 100 52 48 1,118 1,032
15292410 Chulitna River below Canyon near Talkeetna, AK 8/14/2013 11:10 24,100 1,710 0 0 1 22 47 55 58 64 78 89 100 100 55 45 941 770
15292410 Chulitna River below Canyon near Talkeetna, AK 8/14/2013 11:55 24,100 4,070 0 0 1 15 38 52 57 62 70 85 100 100 52 48 2,116 1,954
15292410 Chulitna River below Canyon near Talkeetna, AK 9/10/2013 11:50 28,800 2,930 0 0 0 9 16 23 31 48 72 96 100 100 23 77 674 2,256
15292410 Chulitna River below Canyon near Talkeetna, AK 9/10/2013 12:40 28,800 6,100 0 0 0 8 18 24 30 44 65 83 98 100 24 76 1,464 4,636
15292410 Chulitna River below Canyon near Talkeetna, AK 5/8/2014 11:50 11,700 1,560 0 0 1 24 46 63 70 77 88 100 100 63 37 983 577
15292410 Chulitna River below Canyon near Talkeetna, AK 5/8/2014 12:20 11,700 1,370 0 0 2 36 68 76 82 87 92 100 100 76 24 1,041 329
15292410 Chulitna River below Canyon near Talkeetna, AK 5/22/2014 11:30 11,700 1,510 0 0 1 23 48 55 61 76 88 100 100 55 45 831 680
15292410 Chulitna River below Canyon near Talkeetna, AK 5/22/2014 12:20 11,700 1,640 0 0 2 29 49 58 67 80 90 100 100 58 42 951 689
15292410 Chulitna River below Canyon near Talkeetna, AK 6/25/2014 14:30 20,900 3,590 0 0 1 17 32 40 46 57 69 97 100 40 60 1,436 2,154
15292410 Chulitna River below Canyon near Talkeetna, AK 7/29/2014 11:57 21,200 2,250 0 0 1 14 28 36 41 53 69 100 100 36 64 810 1,440
15292410 Chulitna River below Canyon near Talkeetna, AK 8/26/2014 11:30 16,900 3,670 0 0 0 7 36 47 53 62 75 90 100 100 47 53 1,725 1,945
15292410 Chulitna River below Canyon near Talkeetna, AK 9/16/2014 13:15 20,700 2,680 0 0 0 5 19 29 35 44 62 88 100 100 29 71 777 1,903
15292700 Talkeetna River at Talkeetna, AK 5/31/2013 15:30 24,100 3,960 0 0 0 1 3 5 7 16 35 69 100 100 5 95 198 3,762
15292700 Talkeetna River at Talkeetna, AK 5/31/2013 16:30 24,200 4,770 0 0 1 3 7 15 22 32 47 74 100 100 15 85 716 4,055
15292700 Talkeetna River at Talkeetna, AK 7/10/2013 14:30 6,420 1,700 0 0 1 50 93 98 99 99 100 100 100 100 98 2 1,666 34
15292700 Talkeetna River at Talkeetna, AK 7/10/2013 15:05 6,420 1,470 0 0 2 51 94 99 100 100 100 100 100 100 99 1 1,455 15
15292700 Talkeetna River at Talkeetna, AK 8/13/2013 14:25 7,630 906 0 1 7 61 96 98 98 98 99 100 100 100 98 2 888 18
15292700 Talkeetna River at Talkeetna, AK 8/13/2013 15:05 7,500 1,470 0 0 4 47 88 96 96 97 98 100 100 100 96 4 1,411 59
15292700 Talkeetna River at Talkeetna, AK 9/5/2013 16:10 15,100 1,310 0 0 4 41 80 88 88 89 90 94 100 100 88 12 1,153 157
15292700 Talkeetna River at Talkeetna, AK 9/5/2013 16:50 15,100 643 0 0 4 62 89 94 94 95 97 100 100 100 94 6 604 39
15292700 Talkeetna River at Talkeetna, AK 9/25/2013 16:40 5,160 526 0 0 1 35 93 100 100 100 100 100 100 100 100 0 526 0.0
15292700 Talkeetna River at Talkeetna, AK 9/25/2013 17:20 5,190 949 0 0 2 39 96 100 100 100 100 100 100 100 100 0 949 0.0
15292700 Talkeetna River at Talkeetna, AK 5/6/2014 16:10 6,700 242 0 0 8 60 90 98 99 100 100 100 100 100 98 2 237 5
15292700 Talkeetna River at Talkeetna, AK 5/6/2014 17:10 6,700 260 0 0 4 64 98 100 100 100 100 100 100 100 100 0 260 0.0
15292700 Talkeetna River at Talkeetna, AK 5/20/2014 12:30 6,210 643 0 0 2 48 93 99 100 100 100 100 100 100 99 1 637 6
15292700 Talkeetna River at Talkeetna, AK 5/20/2014 13:20 6,210 519 0 0 2 36 81 96 98 99 100 100 100 100 96 4 498 21
15292700 Talkeetna River at Talkeetna, AK 6/24/2014 14:00 9,160 619 0 0 2 41 75 88 90 92 94 100 100 88 12 545 74
15292700 Talkeetna River at Talkeetna, AK 6/24/2014 14:34 9,160 1,460 0 0 2 28 69 88 92 95 98 88 12 1,285 175
15292700 Talkeetna River at Talkeetna, AK 7/28/2014 16:46 6,790 1,140 0 0 1 36 85 95 96 97 98 100 100 95 5 1,083 57
15292700 Talkeetna River at Talkeetna, AK 9/25/2014 10:50 5,590 393 0 0 0 21 83 99 100 100 100 100 100 100 99 1 389 4
15292780 Susitna River at Sunshine 5/22/2012 14:00 35,100 957 0 0 1 41 54 55 55 56 58 64 90 100 55 45 526 431
15292780 Susitna River at Sunshine 5/22/2012 16:10 35,100 779 0 0 0 11 13 14 14 16 23 40 100 100 14 86 109 670
15292780 Susitna River at Sunshine 6/5/2012 17:50 61,300 1,550 0 0 1 43 66 71 74 77 82 90 100 100 71 29 1,101 450
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Gage
Number Gage Name Date of
Collection
Time of
Collection
Discharge Bedload Sediment
Discharge, Qs
Bedload Sediment,
Percent finer than size indicated, in millimeters Sand Gravel Sediment Discharge,
Qs, Sand
Sediment Discharge,
Qs, Gravel
(cfs) (tons/day) 0.0625 0.125 0.25 0.5 1 2 4 8 16 31.5 63 128 % % (tons/day) (tons/day)
15292780 Susitna River at Sunshine 6/5/2012 18:30 61,300 1,500 0 1 2 40 57 61 65 69 75 86 100 100 61 39 915 585
15292780 Susitna River at Sunshine 7/10/2012 19:00 53,900 518 0 0 1 66 89 91 92 93 95 100 100 100 91 9 471 47
15292780 Susitna River at Sunshine 7/10/2012 19:40 53,900 648 0 1 2 70 90 93 94 96 99 100 100 100 93 7 603 45
15292780 Susitna River at Sunshine 8/13/2012 15:40 43,400 3,700 0 0 0 14 25 33 55 81 96 100 100 100 33 67 1,221 2,479
15292780 Susitna River at Sunshine 8/13/2012 16:20 43,400 2,250 0 0 0 15 41 47 54 65 81 91 100 100 47 53 1,058 1,193
15292780 Susitna River at Sunshine 8/24/2012 13:08 37,000 1,340 0 1 1 36 50 51 55 67 89 98 100 100 51 49 683 657
15292780 Susitna River at Sunshine 8/24/2012 13:40 37,000 579 0 0 1 43 69 73 74 77 87 100 100 100 73 27 423 156
15292780 Susitna River at Sunshine 9/17/2012 15:45 69,200 1,910 0 3 7 52 80 83 84 86 89 94 100 100 83 17 1,585 325
15292780 Susitna River at Sunshine 9/17/2012 16:30 69,200 1,840 0 0 2 40 62 65 68 74 85 98 100 100 65 35 1,196 644
15292780 Susitna River at Sunshine near Talkeetna, AK 6/3/2013 16:10 118,000 1,750 0 0 5 22 29 35 41 48 60 76 100 100 35 65 613 1,138
15292780 Susitna River at Sunshine near Talkeetna, AK 6/3/2013 17:00 116,000 2,450 0 0 3 19 24 28 38 50 65 90 100 100 28 72 686 1,764
15292780 Susitna River at Sunshine near Talkeetna, AK 7/11/2013 15:30 48,400 445 0 0 1 52 74 77 80 83 87 100 100 100 77 23 343 102
15292780 Susitna River at Sunshine near Talkeetna, AK 7/11/2013 16:12 48,400 93 0 0 0 20 25 27 30 40 56 64 100 100 27 73 25 68
15292780 Susitna River at Sunshine near Talkeetna, AK 8/12/2013 12:50 48,800 471 0 0 1 69 95 97 98 99 100 100 100 100 97 3 457 14
15292780 Susitna River at Sunshine near Talkeetna, AK 8/12/2013 13:30 49,000 643 0 0 0 34 50 53 56 59 66 83 100 100 53 47 341 302
15292780 Susitna River at Sunshine near Talkeetna, AK 9/6/2013 11:40 84,900 2,810 0 0 1 20 26 27 30 39 59 86 100 100 27 73 759 2,051
15292780 Susitna River at Sunshine near Talkeetna, AK 9/6/2013 12:30 85,000 2,640 0 0 2 35 52 56 59 63 72 82 100 100 56 44 1,478 1,162
15292780 Susitna River at Sunshine near Talkeetna, AK 5/7/2014 14:05 45,800 1,410 0 0 2 57 71 72 73 74 78 100 100 72 28 1,015 395
15292780 Susitna River at Sunshine near Talkeetna, AK 5/7/2014 14:40 45,800 2,200 0 0 2 31 45 48 51 57 71 100 100 48 52 1,056 1,144
15292780 Susitna River at Sunshine near Talkeetna, AK 5/23/2014 10:00 29,000 1,600 0 0 2 53 95 97 97 98 99 97 3 1,552 48
15292780 Susitna River at Sunshine near Talkeetna, AK 5/23/2014 10:50 29,000 2,650 0 0 2 66 92 94 95 96 97 94 6 2,491 159
15292780 Susitna River at Sunshine near Talkeetna, AK 6/23/2014 14:59 55,900 3,410 0 0 1 32 45 48 52 61 75 100 100 48 52 1,637 1,773
15292780 Susitna River at Sunshine near Talkeetna, AK 7/31/2014 10:58 48,600 1,880 0 0 1 25 37 39 40 46 65 100 100 39 61 733 1,147
15292780 Susitna River at Sunshine near Talkeetna, AK 8/28/2014 10:40 47,200 970 0 0 0 9 51 57 59 64 73 96 100 100 57 43 553 417
15294345 Yentna River near Susitna Station 6/12/2013 16:45 60,500 15,750 0 0 5 59 83 89 92 96 99 100 100 100 89 11 14,018 1,733
15294345 Yentna River near Susitna Station 6/12/2013 18:00 60,800 16,470 0 0 4 55 79 85 89 93 96 85 15 14,000 2,471
15294345 Yentna River near Susitna Station 7/9/2013 11:35 53,200 10,910 0 0 3 53 81 88 92 96 99 100 100 100 88 12 9,601 1,309
15294345 Yentna River near Susitna Station 7/9/2013 12:25 52,900 9,080 0 0 4 50 78 86 90 95 99 100 100 100 86 14 7,809 1,271
15294345 Yentna River near Susitna Station 8/20/2013 10:07 46,100 11,280 0 0 5 57 84 90 93 97 99 100 100 100 90 10 10,152 1,128
15294345 Yentna River near Susitna Station 8/20/2013 11:00 46,000 7,270 0 0 4 48 79 87 90 95 98 100 100 100 87 13 6,325 945
15294345 Yentna River near Susitna Station 9/11/2013 12:40 79,700 3,970 0 0 7 52 79 85 89 94 98 100 100 100 85 15 3,375 596
15294345 Yentna River near Susitna Station 9/11/2013 13:50 80,000 7,260 0 0 7 54 81 88 92 98 98 100 100 100 88 12 6,389 871
15294345 Yentna River near Susitna Station 5/15/2014 11:55 32,500 3,440 0 0 5 52 78 88 93 97 99 88 12 3,027 413
15294345 Yentna River near Susitna Station 5/15/2014 12:45 32,500 4,580 0 0 2 45 77 86 90 93 98 86 14 3,939 641
15294345 Yentna River near Susitna Station 5/28/2014 9:40 33,800 4,830 0 0 4 48 78 86 91 96 99 86 14 4,154 676
15294345 Yentna River near Susitna Station 5/28/2014 10:20 33,800 5,290 0 0 5 50 83 90 94 98 100 100 100 100 90 10 4,761 529
15294345 Yentna River near Susitna Station 7/2/2014 10:32 57,100 5,100 0 0 3 47 75 84 88 92 98 84 16 4,284 816
15294345 Yentna River near Susitna Station 8/7/2014 9:29 45,400 7,390 0 0 3 51 86 92 95 97 99 100 100 100 92 8 6,799 591
15294345 Yentna River near Susitna Station 9/4/2014 9:13 26,800 3,790 0 0 1 28 72 85 91 96 100 100 100 100 85 15 3,222 569
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Gage
Number Gage Name Date of
Collection
Time of
Collection
Discharge Bedload Sediment
Discharge, Qs
Bedload Sediment,
Percent finer than size indicated, in millimeters Sand Gravel Sediment Discharge,
Qs, Sand
Sediment Discharge,
Qs, Gravel
(cfs) (tons/day) 0.0625 0.125 0.25 0.5 1 2 4 8 16 31.5 63 128 % % (tons/day) (tons/day)
15294345 Yentna River near Susitna Station 9/15/2014 13:45 65,000 2,620 0 0 1 12 52 66 73 83 96 100 100 100 66 34 1,729 891
15294350 Susitna River at Susitna Station 6/13/2013 10:55 140,000 6,210 0 0 7 22 43 58 66 76 87 97 100 100 58 42 3,602 2,608
15294350 Susitna River at Susitna Station 6/13/2013 11:42 139,000 4,850 0 0 3 26 55 68 75 84 92 99 100 100 68 32 3,298 1,552
15294350 Susitna River at Susitna Station 7/9/2013 14:40 100,000 5,990 0 0 5 70 86 89 92 95 99 100 100 100 89 11 5,331 659
15294350 Susitna River at Susitna Station 7/9/2013 15:30 100,000 7,140 0 0 17 89 96 97 97 98 99 100 100 100 97 3 6,926 214
15294350 Susitna River at Susitna Station 8/19/2013 12:14 88,000 6,680 0 0 13 73 89 92 93 95 97 98 100 100 92 8 6,146 534
15294350 Susitna River at Susitna Station 8/19/2013 13:23 88,500 3,780 0 0 7 67 89 92 93 96 98 100 100 100 92 8 3,478 302
15294350 Susitna River at Susitna Station 9/12/2013 10:40 176,000 8,430 0 0 6 37 63 75 82 88 94 98 100 100 75 25 6,323 2,108
15294350 Susitna River at Susitna Station 5/15/2014 14:15 79,000 5,350 0 0 2 46 86 93 96 97 99 93 7 4,976 375
15294350 Susitna River at Susitna Station 5/15/2014 15:00 79,000 1,350 0 0 1 30 67 86 93 98 100 100 100 86 14 1,161 189
15294350 Susitna River at Susitna Station 5/28/2014 16:50 72,700 6,470 0 0 2 51 77 84 88 92 98 84 16 5,435 1,035
15294350 Susitna River at Susitna Station 5/28/2014 17:30 72,700 6,760 0 0 3 46 71 79 84 89 96 79 21 5,340 1,420
15294350 Susitna River at Susitna Station 7/1/2014 17:55 134,000 8,180 0 0 5 50 75 81 83 88 93 100 100 81 19 6,626 1,554
15294350 Susitna River at Susitna Station 8/5/2014 13:43 90,900 4,560 0 0 7 50 71 79 84 89 95 99 100 100 79 21 3,602 958
15294350 Susitna River at Susitna Station 9/3/2014 12:42 65,100 1,720 0 0 1 37 81 88 91 95 99 100 100 100 88 12 1,514 206
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Table 5.2-5. USGS Bed Material Data Collected in 2012, 2013, and 2014.
Gage
Number Gage Name Date of
Collection
Time of
Collection
Discharge Bed Material Sediment,
Percent finer than size indicated, in millimeters Sand Gravel
(cfs) 0.125 0.25 0.5 1 2 4 8 16 32 64 128 256 512 1024 % %
15291700 Susitna R above Tsusena Creek 10/12/2012 13:30 10,100 0 16 18 18 18 18 19 20 33 52 75 92 96 100 18 82
15291700 Susitna R above Tsusena Creek 9/4/2013 10:30 20,800 0 26 26 26 26 26 26 28 33 42 57 74 92 100 26 74
15291700 Susitna R above Tsusena Creek 9/29/2014 16:30 8,420 22 25 33 42 61 84 97 99 22 88
15292100 Susitna River near Talkeetna, AK 9/25/2013 13:00 11,300 0 0 12 12 12 12 13 20 36 60 86 96 99 100 12 88
15292100 Susitna River near Talkeetna, AK 9/30/2014 19:00 7 13 30 49 82 96 98 100 7 93
15292400 Chulitna River near Talkeetna, AK 10/21/2013 13:00 15,500 0 0 36 36 36 36 38 44 53 65 80 91 96 100 36 64
15292700 Talkeetna River at Talkeetna, AK 9/9/2013 15:40 11,200 0 0 0 0 0 0 0 0 0 59 100 100 100 100 0 100
15292700 Talkeetna River near Talkeetna, AK 9/25/2014 15:00 5,590 52 75 97 100 100 100 0 100
15292780 Susitna River at Sunshine near Talkeetna, AK 10/22/2013 15:00 29,100 0 0 23 23 23 24 31 40 60 89 99 100 100 100 23 77
15292780 Susitna River at Sunshine near Talkeetna, AK 9/30/2014 13:10 23,700 0 0 20 22 26 40 60 84 99 100 100 100 20 80
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Table 5.8-1. Geomorphic notes of Upper River tributaries previously selected for study of potential delta formation.
Tributary PRM Bank
Presence of
Fan during
August
2014 Recon
~El. @
Mouth
(ft.
NAVD88)
Evidence
of recent
sedimen-
tation
Frequency
sediment
loading Notes
Oshetna
River 235.1 LB yes 2,100 yes
annual-
high
loading
Plane bed river that has incised into its fan. Heavily armored and vertically stable. Ice
scars are present about 10 feet above water surface elevation or more. Appears to be
a substantial sediment source.
Goose
Creek 232.8 LB yes 2,060 unclear episodic
Uniform lag deposits (boulder and cobble) and imbricate material (gravel and cobble)
on large fan. Ice effect on left bank of tributary in moraine which could be source for
the sediment deposited at the mouth. Tributary likely not producing much sediment;
appears deposition occurs because Goose Creek mouth is just upstream of a
constriction on the Susitna River. The constriction, combined with ice effects, likely
dire fan formation. Large cobbles and boulders on fan with some gravel.
Jay Creek 211 RB yes 1,700 yes episodic
Recent episodic event caused avulsion up tributary and sheet flooding downstream.
Event transported material about 128 mm in diameter. Large presence of sand.
Channel downcutting through fan deposits but has been filled with sediment and LWD
from a recent event. Thus, current channel now perched above previous channel
causing sheet flow and less sediment transport. Very unstable channel.
Kosina
Creek 209.1 LB yes 1,680 no episodic
Very stable, granite dominated channel with well-defined floodplain. Boulders greater
than 3 ft present. Channel does not appear to produce much sediment but has high
transport capacity. Presence of some fan in Susitna River that is boulder armored.
Creek appears to have incised down into its fan. Boulders at mouth of creek combined
with bedrock on Susitna river right provide enough constriction for a backwater and
sediment storage zone upstream on the Susitna River.
Watana
Creek 196.9 RB yes 1,550 yes
annual -
high
loading
Recent landslides upstream in tributary basin that are still failing. Large presence of
source material in lower portion of tributary basin; till with boulders up side valleys.
Wide valley, many bars, and fairly open floodplain. Large landslide dammed the river
then had dam break which resulted in huge deposition area. Erosion through landslide
creating turbidity. Older landslides further upstream. Presence of scarps and slumps
all over basin. Presence of mudstones and sedimentary rocks.
Deadman
Creek 189.4 RB yes 1,510 yes
episodic -
low loading
Stable channel. Coarse material at mouth. Doesn't appear to be producing much
sediment. Major waterfalls up tributary. Bedrock controlled sinuosity. Some till
producing sediment, otherwise coarse material. Flatter (upstream) reach has some
sand and fine gravel. Tributary meanders through till deposits where the smaller
material has been cleaned out and a boulder dominated channel is left. Upper
watershed has sand over coarse bed. Very low gradient, high sinuosity in upper
watershed but doesn't seem to be transported to lower reaches. Channel fluctuates to
boulder dominated with sand deposits intermittent up to Deadman Lake.
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Table 5.9-1. Large Woody Debris (LWD) Digitized from Aerial Photographs.
Aerial
photograph
year
Date(s) of aerial photographs Area (PRM) Entire area or LWD sample area?
1950s n/a n/a Not digitized – poor resolution
1983 9/6/1983, 9/11/1983 PRM 3.3 to PRM 159.5 LWD sample areas
2012 9/30/2012, 10/10/2012 PRM 3.3 to PRM 69 LWD sample areas
9/30/2012, 10/10/2012 PRM 69 to PRM 143.6 Entire area
9/30/2012, 10/20/2012 PMR 143.6 to PRM 250 LWD sample areas
2013 9/20/2013 PRM 3.3 to PRM 69 Entire area
9/20/2013, 9/24/2013 PRM 69 to PRM 143.6 LWD sample areas
9/16/2013, 9/20/2013, 9/24/2013,
11/6/2013
PMR 143.6 to PRM 260 Entire area
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Table 5.10-1. Characteristics of stream crossings along the Denali East and portions of the Denali West access routes.
Crossing
Number
Description Estimated
Width (ft)
Confinement Substrate Meandering? LWD
Potential
Photos
1
(Deadman
Creek)
Rapids 80 Unconfined Boulder/Cobble Yes Low 128-131
2 Step Pool 6 Moderately
Confined
Boulder/Cobble No Low 132-133
3 (Delusion
Creek)
Low Gradient
Beaver Ponds,
very wet area
10, braided Unconfined Fines Moderate Moderate 135-137
4 Riffle Run 12 Unconfined Boulder/Cobble Low Low 140-144
5 Riffle Run with
beaver dams
10 Unconfined Gravel/Cobble Moderate Low 147-150
6
(Deadman
Creek
tributary)
Step
Pool/Cascade
8, braided Varies Boulder/Cobble Varies Low/Moderate 154-156
7 Boulder
Cascade
10 Moderately
Confined
Boulder/Cobble Low Moderate 157-158
8 Riffle Run 12 Unconfined Gravel/Cobble Moderate Low 159-160
9 Step
Pool/Cascade
– 2 channels
6, 3 Unconfined Boulder/Cobble Moderate Moderate 165-166
10 Step
Pool/Cascade
4 Unconfined Coble Low Low 167-168
11 Step
Pool/Cascade
– 2 channels
6, 2 Varies Boulder/Cobble Low Moderate 171-173
12 Riffle Cascade
– 2 channels,
high sediment
load
6, braided Varies Boulder/Cobble/
Gravel
Moderate Moderate 175-177
13 Braided Riffle /
Cascade, high
sediment load
8 braided Unconfined Boulder/Cobble/
Gravel
High High 179-181
14 Braided Riffle /
Cascade
8 braided Unconfined Boulder/Cobble/
Gravel
High High 184-186
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Crossing
Number
Description Estimated
Width (ft)
Confinement Substrate Meandering? LWD
Potential
Photos
15 Step Pool 10 Moderately
Confined
Boulder/Cobble Low Moderate/High 189
16 Step
Pool/Cascade
8 Unconfined Boulder/Cobble Low High 218-220
17 (Seattle
Creek)
Step
Pool/Cascade
10 Unconfined Boulder/Cobble Moderate High 223-226
18 (Brush
Kana
Creek)
Beaver
Meadow
n/a Unconfined n/a n/a n/a 227-230
19 Riffle Run
10 Unconfined Cobble/Gravel Moderate Moderate 231-233
20 Riffle Run
50 Unconfined Cobble/Gravel High Low 237-240
21 Riffle Glide 8 Unconfined Cobble/Gravel High Low 243-245
22 Riffle Run 12 Unconfined Cobble/Gravel High Low/Moderate 247-249
23 Riffle Run 6 Unconfined Boulder/Cobble Moderate Moderate 251-252
24 Cascade/Riffle
– 3 channels
6, 5, 4 Unconfined Boulder/Cobble Low Low 254-255
25 Cascade/Riffle
– braided
35 Unconfined Boulder/Cobble Braided Moderate 256-258
26 Step Pool – 2
channels
6, 6 Unconfined Boulder/Cobble Moderate Moderate 261-263
27 Step Pool 6 Moderately
Confined
Boulder/Cobble Moderate Low 266
28
(Deadman
Creek)
Riffle/Cascade
– multi
channel
25 Unconfined Boulder/Cobble Moderate High 268-269
29 Riffle/Cascade 15 Moderately
Confined
Boulder/Cobble Low Low 270-271
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Table 5.11-1: Key used for Table 5.11-2.
Change Trend Level of Potential Effects on River Morphology
Low Moderate High
Decrease – – – – – –
Increase + ++ +++
Little to no effect 0
Table 5.11-2: Initial framework for First-Order analysis of dam effects on river morphology.
Category1 Level of Potential Dam Effects on River Morphology2 Data & Analysis3
Upper River5 Middle River Lower River
FIRST ORDER
1 Hydrology
Qpeak (frequency) 0 – –
~40 %
–
~20 %
Extended and Observed Streamflow Records for the
Susitna River (SIR Study 6.5 Table 5-1 and Tetra
Tech 2013d)
Operational Scenarios (as available) Qbase (duration) 0 ++ +
2 Sediment Supply
sand 0 – / 0 (channel)
– – (floodplain) – Susitna and Tributary Sediment Sampling (SIR Study
6.6 Table 5-1)
USGS sediment data (SIR Study 6.5 Table 5-1)
1-D and 2-D bed evolution modeling (SIR Study 6.6,
Attachment 1) gravel 0 – / 0 0
3 Ice4
Dominant Regime Ice Ice + Fluvial Fluvial
Ice Studies & models (ISR Study 7.6)
1980's Observed Ice Jams (ISR Study 7.6) Processes
Freeze-up
?
(limited local effects
at head of reservoir)
–
(later and less extensive) 0
Break-up 0 Thermal
0 / –
Dynamic
– / – – 0
Extent/Timing 0 0 – 0
4 Geology
Geomorphic Setting Extensive Glacial
deposits
Extensive Glacial
deposits
Extensive Glacial
deposits Mapping Observations: Geomorphic Surface
Mapping in FAs (Table 5-1 and ISR Study 6.5)
Little Ice Age Terraces (SIR Study 6.5 Table 5.1-1
and 5.1-2)
Comparative Thalweg Profile (1980s/2012/2013)
(Tetra Tech 2014a)
Controls (i.e. sensitivity) Extensive Outcrop Extensive Outcrop Tributaries (large)
Bed Material Lag Deposits 0
frequent
0
frequent
0
infrequent
Inherited glacial and paraglacial
features
moraines and
outwash terraces
Tributary Fans and
outwash terraces
Outwash and glacio-
lacustrine terraces
Notes:
1 Aspect of the river system that may change due to dam implementation. It is divided into 1st and 2nd order components. Each component is numbered and broken into further categories, where applicable, that may be affected.
2 Values in cells indicate change or trend and level of potential effects, where applicable. Effects do not consider potential operational changes to reduce or mitigate effects.
3 This column is populated with data that supports the assessment in change trend. The text italicized and in parenthesis indicates where the data can be found.
4 Depends on ice regime as a function of project operation. Flooding and the disturbance regime vary based on thermal versus dynamic ice break-up regimes.
5 Upper River Segment project effects limited to the reservoir area
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Table 5.11-3: Initial framework for Second-Order dam effects analysis.
Category1 Dam Effects2 Data & Analysis (data source)3
Upper River5 Middle River Lower River
Second Order
1 Channel
Aggradation +
Reservoir pool
+
Local Gravel + / –
1-D and 2-D models (SIR Study 6.6 Attachment 1)
Information from other rivers
Degradation 0 0
Armored 0
Width 0 –
Vegetation Encroachment
–
10%
(Has Sand and
Vegetation)
Flow/Sediment Variability (i.e. complexity) 0 Q2 pre v Q2 post, – –
Sedpre v Sedpost, – – –
Q2 pre v Q2 post, –
Sedpre v Sedpost,–
2 Bed Material
Coarse (Gravel and larger) 0 +
(Less Sand) 0 Incipient Motion Analysis (Tetra Tech 2013c)
Sediment Transport Analysis (Tetra Tech 2014b)
1-D and 2-D models (SIR Study 6.6 Attachment 1) Fines (Sand) 0 – –
Reduced Rate
Sediment Transport 0 – – / 0
3 Floodplain
Accretion 0 – – – / 0 Bank Stratifications (SIR Study 6.6 Table 5-1),
Dendrochronology + 210Pb (ISR Study 8.6)
Aerials (1950s, 1980s, 2012, 2013) (SIR Study 6.5
Table 5-1)
Turnover Analysis (Tetra Tech 2014c)
1-D and 2-D Models (SIR Study 6.6 Attachment 1)
Erosion 0 – – / 0
Inundation 0
–
Function of Surface and
Ice Effects
– / 0
4 Planform Single v Multiple channels 0
Could reduce number of
lower order channels if
ice effects are reduced
0
5 Turbidity
Iced-over period 0 + / ++ 0 / +
very small EFDC model (SIR Study 5.5, Attachment 1)
Open water period 0 – / – – 0 / –
very, very small
6 Tributary Impacts f ( size, volume, sediment produced & transport
capacity of the river)
0
+ / – in reservoir
+
Larger fans could impact
upstream ice jams
0 Tributary Sediment Data (SIR Study 6.6 Table 5-1)
Mainstem Hydraulics (Tetra Tech 2014b)
Notes:
1 Aspect of the river system that may change due to dam implementation. It is divided into 1st and 2nd order components. Each component is numbered and broken into further categories, where applicable, that may be affected.
2 Values in cells indicate change or trend and level of potential effects, where applicable. Effects do not consider potential operational changes to reduce or mitigate effects.
3 This column is populated with data that supports the assessment in change trend. The text italicized and in parenthesis indicates where the data can be found.
4 Depends on ice regime as a function of project operation. Flooding and the disturbance regime vary based on thermal versus dynamic ice break-up regimes.
5 Upper River Segment project effects limited to the reservoir area
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10. FIGURES
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Figure 3-1: Susitna River geomorphology study area and large-scale river segments.
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Figure 5.1-1: Upper River Lateral Control and Sediment Source Mapping with illustrative photo numbers noted (See Appendix A for photos) for Upstream Maclaren Confluence - PRM 291.8 to PRM 278.9.
P5582
P774
P775
P5580
P871
P805
P5570
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Figure 5.1-2: Upper River Lateral Control and Sediment Source Mapping with illustrative photo numbers noted (See Appendix A for photos) for Upstream Maclaren River Confluence - PRM 278.9 to PRM 266.7.
P956
P927
P928
P929
P931
P5559
P992
P5557
P028
P038
P040
P042
P5556
P062
P5555
P5554
P5552
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Figure 5.1-3: Upper River Lateral Control and Sediment Source Mapping with illustrative photo numbers noted (See Appendix A for photos) for Upstream Maclaren River Confluence – PRM 266.7 to PRM 261.3.
P074
P080
P082
P090
P082
P112
P082
P551
P082
P138
P082
P5550
P082
P5548
P082
P165
P167
P176
P177
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Figure 5.1-4: Upper River Lateral Control and Sediment Source Mapping with illustrative photo numbers noted (See Appendix A for photos) for geomorphic reach UR-1.
P5547
P082
P260
P219
P220
P5547
P082
P5540
P082
P245
P258
P272
P273
P293
P315
P319
P5538
P5539
P400
P425
P5536
P440
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Figure 5.1-5: Upper River Lateral Control and Sediment Source Mapping with illustrative photo numbers noted (See Appendix A for photos) for geomorphic reach UR-2.
P898
P903
P91
8
P5530
P973
P448
P458
P473
P507
P5526
P554
P618
P611
P65
0
P699
P701
P714
P5529
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Figure 5.1-6: Upper River Lateral Control and Sediment Source Mapping with illustrative photo numbers noted (See Appendix A for photos) for geomorphic reach UR-3.
P750
P757
P069
P033
P032
P5512
P829
P5516
P5516
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Figure 5.1-7: Upper River Lateral Control and Sediment Source Mapping with illustrative photo numbers noted (See Appendix A for photos) for geomorphic reach UR-4.
P5498
P871
P877
P5497
P121
P130
P131
P114
P161
P177
P5491
P5490
P964
P996
P5484
P5481
P371
P5474
P5473
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Figure 5.1-8: Upper River Lateral Control and Sediment Source Mapping with illustrative photo numbers noted (See Appendix A for photos) for geomorphic reach UR-5.
P218
P210
P5466
P188
P206
P5471
P145
P142
P134
P127
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Figure 5.1-9: Upper River Lateral Control and Sediment Source Mapping with illustrative photo numbers noted (See Appendix A for photos) for geomorphic reach UR-6.
P207
P268
P5461
P5459
P5456
P5454
P5453
P5451
P374
P430
P432
P5444
P5438
P484
P486
P5435
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Figure 5.1-10: Cross-section UR 1.1 at PRM 257.9 (Q =- 17,400 cfs at Gold Creek gage).
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Figure 5.1-11: Cross-section UR 1.2 at PRM 253.4 (Q = 16,700 cfs at Gold Creek gage).
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Figure 5.1-12: Cross-section UR 2.1 at PRM 245.4 (Q = 17,000 cfs at Gold Creek gage).
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Figure 5.1-13: Cross-section UR 4.1 at PRM 220.7 (Q = 16,800 cfs at Gold Creek gage).
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Figure 5.8-1: View upstream Oshetna River from confluence with Susitna River. Clear water evident.
Figure 5.8-2. View upstream of Oshetna River fan at confluence with Susitna River. Helicopter access present upstream
and downstream of Oshetna River confluence on Susitna River left.
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Figure 5.8-3. View upstream Goose Creek from confluence with Susitna River. Plane-bed channel evident.
Figure 5.8-4. View downstream Goose Creek to confluence with Susitna River. Armored channel evident with large
sediment deposition and fan at Goose Creek mouth. Slumping left bank along Goose Creek. Safe landing zone present on
Goose Creek fan.
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Figure 5.8-5. View upstream Jay creek above Jay Creek confluence with Susitna River. Log jams present in channel.
Channel filled-in with sand, gravel, boulder, and large wood deposits.
Figure 5.8-6. Upstream Jay Creek fan, looking upstream Susitna River (right bank) along sheet flow from Jay creek. Safe
landing zones present upstream and downstream Jay Creek fan on Susitna River right bank.
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Figure 5.8-7. View downstream Susitna River left bank to Kosina River fan. Plane-bed, boulder-cobble channel evident.
Safe landing zones present upstream and downstream Kosina River confluence along Kosina fan.
Figure 5.8-8. View downstream Watana Creek towards confluence with Susitna River. Gravel deposits present along
Watana Creek right bank.
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Figure 5.8-9. View upstream to Watana Creek (Susitna River right bank). Safe landing zones present along Watana
Creek fan and floodplain.
Figure 5.8-10. View upstream Deadman Creek. Steep, confined, boulder-dominated channel evident.
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Figure 5.8-11. View upstream Susitna River right bank upstream of Deadman Creek fan. Safe landing zones present
upstream and downstream of Deadman Creek confluence with Susitna River.
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Figure 5.9-1. Large Woody Debris (LWD) by Species, 2013/2014 Field Inventory.
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Figure 5.9-2. Large Woody Debris (LWD) by Input Mechanism, 2013/2014 Field Inventory.
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Figure 5.9-3. Large Woody Debris (LWD) by Diameter, 2013/2014 Field Inventory.
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Figure 5.9-4. Large Woody Debris (LWD) by Freshness, 2014 Field Inventory.
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Figure 5.9-5. Large Woody Debris (LWD) by Channel Position, 2014 Field Inventory.
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Figure 5.9-6. LWD Sample area PRM 9-12.
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Figure 5.9-7. LWD Sample area FA-151 Portage Creek.
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Figure 5.9-8. LWD Sample area PRM 169.
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Figure 5.9-9. LWD Sample area FA-173 Stephan Lake Complex.
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Figure 5.9-10. LWD Sample area PRM 181.
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Figure 5.9-11. LWD Sample area FA-184 Watana Dam.
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Figure 5.10-1. Map of access corridor reconnaissance route and stream crossings identified during reconnaissance.