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Susitna-Watana Hydroelectric Project Document
ARLIS Uniform Cover Page
Title:
Technical memorandum: Selection of focus areas and study sites in the
middle and lower Susitna River for instream flow and joint resource studies
- 2013 and 2014 SuWa 200
Author(s) – Personal:
Author(s) – Corporate:
R2 Resource Consultants, Inc.
AEA-identified category, if specified:
Final study plan
AEA-identified series, if specified:
Series (ARLIS-assigned report number):
Susitna-Watana Hydroelectric Project document number 200
Existing numbers on document:
Published by:
[Anchorage : Alaska Energy Authority, 2013]
Date published:
March 1, 2013
Published for:
Alaska Energy Authority
Date or date range of report:
Volume and/or Part numbers:
Study plan Section 8.5A
Final or Draft status, as indicated:
Document type:
Pagination:
3, ix, 77 p.
Related work(s):
Pages added/changed by ARLIS:
Notes:
Consists of a cover letter and Attachment C.
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/
March 1, 2013
Ms. Kimberly D. Bose
Secretary
Federal Energy Regulatory Commission
888 First Street, NE
Washington, DC 20426
Re: Susitna-Watana Hydroelectric Project, FERC Project No. 14241-000;
Submittal of Information Related to Study Plan Determination
Dear Secretary Bose:
By letter dated January 17, 2013, Staff of the Federal Energy Regulatory
Commission (Commission) revised the licensing schedule for the Alaska Energy
Authority’s (AEA) proposed Susitna-Watana Hydroelectric Project, FERC Project No.
14241 (Project).1 Primarily, Commission Staff’s January 17th letter established a process
for its April 1, 2013 issuance of the Study Plan Determination (SPD) for 14 of the
individual study plans included in AEA’s Revised Study Plan (RSP),2 filed with the
Commission on December 14, 2012.3 Leading up to Staff’s April 1 SPD, the January
17th letter required AEA to prepare and file, following consultation with licensing
participants, additional information that Commission Staff have deemed necessary for the
April 1 SPD. The purpose of this filing is to submit the information required by Staff’s
January 17th letter, as well as other relevant information in support of these 14 study
plans.
1 Letter from Jeff C. Wright, Federal Energy Regulatory Commission, to Wayne Dyok, Alaska Energy
Authority, Project No. 14241-000 (issued Jan. 17, 2013) [hereinafter, “January 17th Letter”].
2 Commission Staff’s January 17th letter established April 1 as the SPD date for 13 of the individual
studies in the RSP. January 17th Letter, Attachment A. When issuing the SPD for the other individual
study plans in the RSP, however, Commission Staff postponed its determination on one additional study
until the April 1, 2013 SPD. Letter from Jeff C. Wright, Federal Energy Regulatory Commission, to
Wayne Dyok, Alaska Energy Authority, at 3, Project. No. 14241-000 (issued Feb. 1, 2013). In total, the 14
individual studies scheduled for Staff’s April 1st SPD consist of the following: (1) Baseline Water Quality
(RSP 5.5); (2) Water Quality Modeling Study (RSP 5.6); (3) Mercury Assessment and Potential for
Bioaccumulation Study (RSP 5.7); (4) Geomorphology Study (RSP 6.5); (5) Fluvial Geomorphology
Modeling Below Watana Dam Study (RSP 6.6); (6) Groundwater Study (RSP 7.5); (7) Ice Processes in the
Susitna River Study (RSP 7.6); (8) Fish and Aquatics Instream Flow Study (RSP 8.5); (9) Riparian
Instream Flow Study (RSP 8.6); (10) Study of Fish Distribution and Abundance in the Upper Susitna River
(RSP 9.5); (11) Study of Fish Distribution and Abundance in the Middle and Lower Susitna River (RSP
9.6); (12) River Productivity Study (RSP 9.8); (13) Characterization and Mapping of Aquatic Habitats
(RSP 9.9); and (14) Riparian Vegetation Study Downstream of the Proposed Susitna-Watana Dam (RSP
11.6).
3 Revised Study Plan, Project No. 14241-000 (filed Dec. 14, 2012) [hereinafter, “RSP”].
2
As required by Commission Staff’s January 17th letter, AEA hereby submits the
following documents:
Requested Information 4 Attachment
Final implementation plan for Study of
Fish Distribution and Abundance in the
Upper Susitna River (RSP 9.5)
Attachment A, Final Susitna River Fish
Distribution and Abundance
Implementation Plan (March 2013)
Final implementation plan for Study of
Fish Distribution and Abundance in the
Middle and Lower Susitna River (RSP 9.6)
Attachment A, Final Susitna River Fish
Distribution and Abundance
Implementation Plan (March 2013)
Final implementation plan for River
Productivity Study (RSP 9.8)
Attachment B, Final Susitna River
Productivity Study Implementation Plan
(March 2013)
Final focus areas for 2013 middle and
lower river studies
Attachment C, Technical Memorandum,
Selection of Focus Areas and Study Sites in
the Middle and Lower Susitna River for
Instream Flow and Joint Resource Studies
– 2013 and 2014 (March 2013)
As directed in Staff’s January 17th letter, AEA on January 31, 2013, filed drafts of
all these documents with the Commission and distributed them to licensing participants
via its licensing website, http://www.susitna-watanahydro.org/meetings/. Also in
conformance with Staff’s January 17th letter, AEA held technical workgroup (TWG)
meetings on February 14th and 15th “to discuss the study results, proposed
implementation plans, and selected focus areas in the middle and lower Susitna River.”5
Because Staff of the National Marine Fisheries Service (NMFS) were unavailable to meet
on February 14-15 due to a preexisting scheduling conflict, AEA met separately with
NMFS on February 7th and 8th to review these materials.
In accordance with Commission Staff’s revised licensing schedule, licensing
participants may file comments on the attached implementation plans and technical
memorandum—as well as the 14 studies subject to Staff’s April 1st RSP6—by March 18,
2013.7 Based on the technical information discussed in the February 7 -8 and 14-15
meetings, AEA has made changes to the attached implementation plans and technical
memo since the drafts of these were filed and distributed on January 31.
AEA also has attached two additional documents related to Commission Staff’s
April 1st SPD. First, based on RSP comments filed by the Alaska Department of
4 See January 17th Letter, Attachment A, at 5.
5 Id.
6 These 14 individual study plans can be found in AEA’s RSP, filed with the Commission on December
14, 2012. See supra note 2. The RSP can be accessed from the Commission’s eLibrary system or AEA’s
licensing website, http://www.susitna-watanahydro.org/type/documents/.
7 See January 17th Letter, Attachment A, at 5.
3
Environmental Conservation (DCE),8 AEA has prepared and included as Attachment D
an updated Quality Assurance Project Plan (QAPP) for the Baseline Water Quality Study
(RSP 5.5).9 The attached QAPP has been updated to conform with DEC’s Quality
Assurance Plan Review Checklist and Draft Guidance for a Tier 2 Water Quality
Monitoring QAPP.10 Second, as discussed in the meetings with NMFS on February 7-8
and the TWG on February 14-15, AEA has prepared and attached as Attachment E a
response to interim comments submitted by NMFS and the U.S. Fish and Wildlife
Service on Characterization and Mapping of Aquatic Habitat Mapping Revised Study
Plan (RSP 9.9), including a comparison table demonstrating that there is no significant
difference between AEA’s habitat classification system and the classification system
promoted by the resource agencies.
As always, AEA appreciates the participation and commitment to this licensing
process demonstrated by Commission Staff, federal and state resource agencies, and
other licensing participants. Following Commission Staff’s April 1st SPD, AEA looks
forward to working with licensing participants and Commission Staff in implementing
the approved studies, which AEA believes will comprehensively investigate and evaluate
the full range of resource issues associated with the proposed Project and support AEA’s
license application, scheduled to be filed with the Commission in 2015.
If you have questions concerning this submission please contact me at
wdyok@aidea.org or (907) 771-3955.
Sincerely,
Wayne Dyok
Project Manager
Alaska Energy Authority
Attachments
cc: Distribution List (w/o Attachments)
8 State of Alaska Resource Agency RSP Comments, Project No. 14241-000, at 3-6 (filed Jan. 18, 2013)
[hereinafter, “DEC RSP Comments”].
9 See RSP § 5, Attachment 5-1.
10 DEC RSP Comments, Attachments 1 & 2.
Attachment C
Technical Memorandum, Selection of Focus Areas and Study Sites in the Middle and Lower
Susitna River for Instream Flow and Joint Resource Studies – 2013 and 2014 (March 2013)
Susitna-Watana Hydroelectric Project
(FERC No. 14241)
Technical Memorandum
Selection of Focus Areas and Study Sites in the Middle
and Lower Susitna River for Instream Flow and Joint
Resource Studies – 2013 and 2014
Prepared for
Alaska Energy Authority
Prepared by
R2 Resource Consultants, Inc.
March 1, 2013
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page i March 2013
TABLE OF CONTENTS
1. Introduction ........................................................................................................................1
1.1. Background and Context of this technical memorandum ..................................1
1.2. Objectives ..........................................................................................................3
2. Review of River Stratification and Study Area Selection Process ................................4
2.1. Selection of Study Areas/Study Sites ................................................................6
2.1.1. Representative Sites ........................................................................ 6
2.1.2. Critical Sites .................................................................................... 7
2.1.3. Randomly Located Sites ................................................................. 7
2.1.4. Focus Areas ..................................................................................... 7
3. Middle River Segment Study Site Selection ....................................................................8
3.1. Focus Areas ........................................................................................................8
3.1.1. Fish and Aquatics IFS Evaluation of Focus Areas ....................... 10
3.1.2. Riparian Process Domain Delineation and Evaluation of Focus
Areas ............................................................................................. 14
3.2. Sites Outside of the Focus Areas .....................................................................16
3.3. Final Listing of Focus Areas and Study Sites for Middle River Segment .......17
4. Study Sites Identified in the Lower River Segment ......................................................20
4.1. Rationale for Extending Studies into the Lower River Segment .....................20
4.2. Resource Specific Studies and Study Sites in Lower River Segment .............24
4.2.1. Fish and Aquatics Instream Flow Study ....................................... 24
4.2.2. Riparian Instream Flow Study ...................................................... 27
4.2.3. Groundwater ................................................................................. 28
4.2.4. Fisheries ........................................................................................ 28
4.2.5. Geomorphology ............................................................................ 29
4.2.6. Ice Processes ................................................................................. 31
4.2.7. Water Quality ................................................................................ 32
5. References .........................................................................................................................34
6. Tables ................................................................................................................................36
7. Figures ...............................................................................................................................55
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page ii March 2013
LIST OF TABLES
Table 1. Locations, descriptions and selection rationale of final Focus Areas for detailed study in
the Middle River Segment of the Susitna River. Focus Area identification numbers (e.g.,
Focus Area 184) represent the truncated Project River Mile (PRM) at the downstream end
of each Focus Area. ............................................................................................................... 37
Table 2. Main channel habitat classifications by geomorphic reach in the Middle Susitna River.
............................................................................................................................................... 38
Table 3. Main Channel mesohabitat classifications in the Middle Susitna River. ...................... 39
Table 4. Off channel habitats classified in the Middle Susitna River. ......................................... 40
Table 5. Tributary features classified in the Middle Susitna River. Potential fish-bearing
tributaries were identified as a subset of those classified by the habitat mapping. .............. 41
Table 6. Metrics used to compare the representation and proportionality of habitat types between
focus areas and non-focus areas within each geomorphic reach. ......................................... 41
Table 7. Estimated bias for each proportionality metric (total for reach – focus area) where
estimates could be made. Statistical comparison was made using a t-test or nonparametric
alternative when the sample size (number of geomorphic reaches with bias estimate) was
greater than three. .................................................................................................................. 42
Table 8. Identification of existing focus area boundaries and counterpart locations of areas
selected via a random systematic approach. ......................................................................... 42
Table 9. Comparison of simulated random focus areas to project focus areas by geomorphic
reach for main channel habitat (FA=project focus areas; RFA=random systematic focus
areas, Total=Total for the geomorphic reach.) ...................................................................... 43
Table 10. Estimated bias for each proportionality metric (total for reach – focus area) where
estimates could be made for random focus areas. Statistical comparison was made using a
t-test or nonparametric alternative when the sample size (number of geomorphic reaches
with bias estimate) was greater than three. ........................................................................... 44
Table 11. Riparian process domain #1 (RPD1). Plant communities typed, and measured, along
transects using Alaska Vegetation Classification (AVC) Level III (1992) community
descriptions. First column describes communities identified along transects in RPD1 and
remaining columns describe communities within Focus Areas in the riparian process
domain. The sum of lengths (line-intercept sampling method; length in meters) for each
cover type are reported in parentheses. ................................................................................. 45
Table 12. Riparian process domain #3 (RPD3). Plant communities typed, and measured, along
transects using Alaska Vegetation Classification (AVC) Level III (1992) community
descriptions. First column describes communities identified along transects in RPD3 and
remaining columns describe communities within Focus Areas in the riparian process
domain. The sum of lengths (line-intercept sampling method; length in meters) for each
cover type are reported in parentheses. ................................................................................. 46
Table 13. Riparian process domain #4 (RPD4). Plant communities typed, and measured, along
transects using Alaska Vegetation Classification (AVC) Level III (1992) community
descriptions. First column describes communities identified along transects in RPD4 and
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page iii March 2013
remaining columns describe communities within Focus Areas in the riparian process
domain. The sum of lengths (line-intercept sampling method; length in meters) for each
cover type are reported in parentheses. ................................................................................. 47
Table 14. Rationale for Riparian IFS Focus Area selection ........................................................ 48
Table 15. List of Focus Areas selected for Riparian-IFS studies within each Riparian Process
Domain. ................................................................................................................................. 48
Table 16. Partial list of river cross-sections, and flow and water surface elevations measured in
2012 on the Susitna River between River Miles 75 and 184. The list does not include
additional measurements in late September/October. Those measurements had not been
processed at the time this study plan was prepared. ............................................................. 49
Table 17. Habitat types by geomorphic reach and how representativeness will be achieved.
(FA=Focus Area; CS=Cross-section). .................................................................................. 52
Table 18. Summary of Potential Effects of With-Project Flows on Tributaries of the Lower
Susitna River from 1980s studies, and tributary mouths proposed for modeling in 2013
(indicated by highlighting) (1980s summary adapted from Ashton and Trihey (1985)). ..... 53
Table 19. List of Lower River 2013 Riparian Vegetation Sampling Transects, and Geomorphic
Reach Types (Tetra Tech, 2013d). ........................................................................................ 53
Table 20. Proposed Susitna River Basin Temperature and Water Quality Monitoring Sites. ..... 54
LIST OF FIGURES
Figure 1. Map of the Middle Segment of the Susitna River depicting the eight Geomorphic
Reaches and locations of proposed Focus Areas. No Focus Areas are proposed for in MR-3
and MR-4 due to safety issues related to sampling within or proximal to Devils Canyon. .. 56
Figure 2. Map of the Lower Segment of the Susitna River depicting the six Geomorphic
Reaches. Focus Areas have not been identified in this segment but will be considered
pending results of open-water flow routing modeling. ......................................................... 57
Figure 3. Map showing Focus Area 184 that begins at Project River Mile 184.7 and extends
upstream to PRM 185.7. The Focus Area is located about 1.4 miles downstream of the
proposed Watana Dam site near Tsusena Creek. .................................................................. 58
Figure 4. Map showing Focus Area 173 beginning at Project River Mile 173.6 and extends
upstream to PRM 175.4. This Focus Area is near Stephan Lake and consists of main
channel and a side channel complex. .................................................................................... 59
Figure 5. Map showing Focus Area 171 beginning at Project River Mile 171.6 and extends
upstream to PRM 173. This Focus Area is near Stephan Lake and consists of main channel
and a single side channel with vegetated island. ................................................................... 60
Figure 6. Map showing Focus Area 151 beginning at Project River Mile 151.8 and extends
upstream to PRM 152.3. This single main channel Focus Area is at the Portage Creek
confluence. ............................................................................................................................ 61
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page iv March 2013
Figure 7. Map showing Focus Area 144 beginning at Project River Mile 144.4 and extends
upstream to PRM 145.7. This Focus Area is located about 2.3 miles upstream of Indian
River and includes Side Channel 21 and Slough 21. ............................................................ 62
Figure 8. Map showing Focus Area 141 beginning at Project River Mile 141.8 and extends
upstream to PRM 143.4. This Focus Area includes the Indian River confluence and a range
of main channel and off-channel habitats. ............................................................................ 63
Figure 9. Map showing Focus Area 138 beginning at Project River Mile 138.7 and extends
upstream to PRM 140. This Focus Area is near Gold Creek and consists of a complex of
side channel, side slough and upland slough habitats including Upper Side Channel 11 and
Slough 11. ............................................................................................................................. 64
Figure 10. Map showing Focus Area 128 beginning at Project River Mile 128.1 and extends
upstream to PRM 129.7. This Focus Area consists of side channel, side slough and
tributary confluence habitat features including Skull Creek. ................................................ 65
Figure 11. Map showing Focus Area 115 beginning at Project River Mile 115.3 and extends
upstream to PRM 116.5. This Focus Area is located about 0.6 miles downstream of Lane
Creek and consists of side channel and upland slough habitats including Slough 6A. ........ 66
Figure 12. Map showing Focus Area 104 beginning at Project River Mile 104.8 and extends
upstream to PRM 106. This Focus Area covers the diverse range of habitats in the
Whiskers Slough complex. ................................................................................................... 67
Figure 13. Percent of main channel in single main, split main, and braided main channel habitat
by geomorphic reach and focus area (F), non-focus area (NF), and total (T). ..................... 68
Figure 14. Side channel, side slough, and upland slough lengths per mile of main channel by
geomorphic reach and focus area (F), non-focus area (NF), and total (T). .......................... 69
Figure 15. Percent of slough habitat that is in beaver complex by geomorphic reach and focus
area (F), non-focus area (NF), and total (T). ......................................................................... 69
Figure 16. Backwaters, tributaries, tributary mouths, and plumes density (#/mile) by geomorphic
reach and focus area (F), non-focus area (NF), and total (T). ............................................... 70
Figure 17. Percent of main and side channel habitat that is in riffle vs. glide/run habitat by
geomorphic reach and focus area (F), non-focus area (NF), and total (T). .......................... 70
Figure 18. Riparian Process Domains on the Middle River with locations of associated Riparian
IFS Focus Areas. ................................................................................................................... 71
Figure 19. Locations of habitat types missing from the Focus Areas by Geomorphic Reach.
Habitat types included split main channel (MR-2, MR-5), side slough (MR-5), Tributary
mouth (MR-7) and backwater (MR-2 and MR-8). ............................................................... 72
Figure 20. Map of the Lower Segment of the Susitna River depicting the six Geomorphic
Reaches and locations of proposed 2013 study areas for geomorphology, instream flow–
fish, instream flow-riparian and fish distribution and abundance. ........................................ 73
Figure 21. Map showing proposed location of lower Susitna River instream flow-fish habitat
transects in Geomorphic Reach LR-1 in the vicinity of Trapper Creek. The proposed
location, number, angle, and transect endpoints are tentative pending on-site confirmation
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page v March 2013
during open-water conditions. Where feasible, instream flow fish habitat transects will be
co-located with geomorphology, open-water flow routing, and instream flow-riparian
transects. ................................................................................................................................ 74
Figure 22. Map showing proposed location of lower Susitna River instream flow-fish habitat
transects in Geomorphic Reach LR-2 in the vicinity of Caswell Creek. The proposed
location, number, angle, and transect endpoints are tentative pending on-site confirmation
during open-water conditions. Where feasible, instream flow fish habitat transects will be
co-located with geomorphology, open-water flow routing and instream flow-riparian
transects. ................................................................................................................................ 75
Figure 23. Ice Processes Study locations in Lower River. .......................................................... 76
Figure 24. Proposed water quality sample locations for Susitna River. ...................................... 77
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page vi March 2013
LIST OF ACRONYMS AND SCIENTIFIC LABELS
Abbreviation Definition
AEA Alaska Energy Authority
Backwater
Off-channel habitat characterization feature found along channel margins and
generally within the influence of the active main channel with no independent
source of inflow. Water is not clear.
Baseline
Baseline (or Environmental Baseline): the environmental conditions that are the
starting point for analyzing the impacts of a proposed licensing action (such as
approval of a license application) and any alternative.
Beaver complex Off-channel habitat characterization feature consisting of a ponded water body
created by beaver dams.
Braided streams
Stream consisting of multiple small, shallow channels that divide and recombine
numerous times. Associated with glaciers, the braiding is caused by excess
sediment load.
Cascade
The steepest of riffle habitats. Unlike rapids, which have an even gradient,
cascades consist of a series of small steps of alternating small waterfalls and
shallow pools.
Cfs cubic feet per second
Channel A natural or artificial watercourse that continuously or intermittently contains water,
with definite bed and banks that confine all but overbank stream flows.
Conductivity In terms of water conductivity, the ability of water to conduct electricity, normally
through the presence of dissolved solids that carry electrical charges.
Confluence The junction of two or more rivers or streams.
Cross-section A plane across a river or stream channel perpendicular to the direction of water
flow.
Devils Canyon
Located at approximately Susitna River Mile (RM) 150-161, Devils Canyon contains
four sets of turbulent rapids rated collectively as Class VI. This feature is a partial
fish barrier because of high water velocity.
Distribution (species) The manner in which a biological taxon is spatially arranged.
Edge habitat The boundary between natural habitats, in this case between land and a stream.
Level five tier of the habitat classification system.
Escapement (spawning) The number or proportion of fish surviving (escaping from) a given fishery at the
end of the fishing season and reaching the spawning grounds.
et al. “et alia”; and the rest
FA Focus Area
FERC Federal Energy Regulatory Commission
Floodplain
1. The area along waterways that is subject to periodic inundation by out-of-bank
flows. 2. The area adjoining a water body that becomes inundated during periods
of over-bank flooding and that is given rigorous legal definition in regulatory
programs. 3. Land beyond a stream channel that forms the perimeter for the
maximum probability flood. 4. A relatively flat strip of land bordering a stream that
is formed by sediment deposition. 5. A deposit of alluvium that covers a valley flat
from lateral erosion of meandering streams and rivers.
Floodplain vegetation − groundwater /
surface water regime functional groups
Assemblages of plants that have established and developed under similar
groundwater and surface water hydrologic regimes.
Fluvial Of or pertaining to the processes associated with rivers and streams and the
deposits and landforms created by them.
Focus Area Areas selected for intensive investigation by multiple disciplines as part of the AEA
study program.
Geomorphic reach Level two tier of the habitat classification system. Separates major hydraulic
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page vii March 2013
Abbreviation Definition
segments into unique reaches based on the channel’s geomorphic characteristic.
GIS
Geographic Information System. An integrated collection of computer software and
data used to view and manage information about geographic places, analyze
spatial relationships, and model spatial processes.
Glide An area with generally uniform depth and flow with no surface turbulence. Low
gradient; 0-1 % slope.
Gradient The rate of change of any characteristic, expressed per unit of length (see Slope).
May also apply to longitudinal succession of biological communities.
Groundwater (GW) In the broadest sense, all subsurface water; more commonly that part of the
subsurface water in the saturated zone.
Habitat
The environment in which the fish live, including everything that surrounds and
affects its life, e.g., water quality, bottom, vegetation, associated species (including
food supplies). The locality, site and particular type of local environment occupied
by an organism.
Instream flow The rate of flow in a river or stream channel at any time of year.
Juvenile A young fish or animal that has not reached sexual maturity.
licensing participants; Participants Agencies, ANCSA corporations, Alaska Native entities and other licensing
participants
Life stage
An arbitrary age classification of an organism into categories relate to body
morphology and reproductive potential, such as spawning, egg incubation, larva or
fry, juvenile, and adult.
Lower segment Susitna The Susitna River from Cook Inlet (RM 0) to the confluence of the Chulitna River at
RM 98.
LR Lower River Reach
Main channel For habitat classification system: a single dominant main channel. Also, the
primary downstream segment of a river, as contrasted to its tributaries.
Main channel habitat
Level four tier of the habitat classification system. Separates main channel habitat
types including: tributary mouth, main channel, split main channel, multiple split
main channel and side channel into mesohabitat types. Mesohabitat types include
pool, glide, run, riffle, and rapid.
Mainstem
Mainstem refers to the primary river corridor, as contrasted to its tributaries.
Mainstem habitats include the main channel, split main channels, side channels,
tributary mouths, and off-channel habitats.
Mainstem habitat
Level three tier of the habitat classification systems. Separates mainstem habitat
into main channel, off-channel, and tributary habitat types. Main channel habitat
types include: tributary mouth, main channel, split main channel, multiple split main
channel and side channel. Off-channel habitat types include: side slough, upland
slough, backwater, and beaver complex. Tributary habitat is not further
categorized.
Mesohabitat
A discrete area of stream exhibiting relatively similar characteristics of depth,
velocity, slope, substrate, and cover, and variances thereof (e.g., pools with
maximum depth <5 ft, high gradient rimes, side channel backwaters).
Mi mile(s)
Middle segment Susitna The Susitna River from the confluence of the Chulitna River at RM 98 to the
proposed Watana Dam Site at RM 184.
Migrant (life history type) Some species exhibit a migratory life history type and undergo a migration to from
rivers/lakes/ocean.
Migration Systematic (as opposed to random) movement of individuals of a stock from one
place to another, often related to season.
MR Middle River Reach
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page viii March 2013
Abbreviation Definition
Multiple split main channel Main channel habitat characterization feature where more than three distributed
dominant channels are present.
N/A not applicable or not available
Off-channel Those bodies of water adjacent to the main channel that have surface water
connections to the main river at some discharge levels.
Off-channel habitat Habitat within those bodies of water adjacent to the main channel that have surface
water connections to the main river at some discharge levels.
PHABSIM
Physical Habitat Simulation, a specific model designed to calculate an index to the
amount of microhabitat available for different life stages at different flow levels.
PHABSIM has two major analytical components: stream hydraulics and life stage-
specific habitat requirements.
Pool Slow water habitat with minimal turbulence and deeper due to a strong hydraulic
control.
PRM
Project River Mile(s) based on the digitized wetted width centerline of the main
channel from 2012 Matanuska-Susitna Borough digital orthophotos. PRM 0.0 is
established as mean lower low water of the Susitna River confluence at Cook Inlet.
Project Susitna-Watana Hydroelectric Project
PSP Proposed Study Plan
Radiotelemetry Involves the capture and placement of radio-tags in adult fish that allow for the
remote tracking of movements of individual fish.
Rapid
Swift, turbulent flow including small chutes and some hydraulic jumps swirling
around boulders. Exposed substrate composed of individual boulders, boulder
clusters, and partial bars. Lower gradient and less dense concentration of boulders
and white water than Cascade. Moderate gradient; usually 2.0-4.0% slope.
Rearing Rearing is the term used by fish biologists that considers the period of time in which
juvenile fish feed and grow.
Riffle
A fast water habitat with turbulent, shallow flow over submerged or partially
submerged gravel and cobble substrates. Generally broad, uniform cross-section.
Low gradient; usually 0.5-2.0% slope.
Riparian Pertaining to anything connected with or adjacent to the bank of a stream or other
body of water.
River A large stream that serves as the natural drainage channel for a relatively large
catchment or drainage basin.
River mile The distance of a point on a river measured in miles from the river's mouth along
the low-water channel.
RM River Mile(s) referencing those of the APA Project.
RSP Revised Study Plan
Run (habitat)
A habitat area with minimal surface turbulence over or around protruding boulders
with generally uniform depth that is generally greater than the maximum substrate
size. Velocities are on border of fast and slow water. Gradients are approximately
0.5 % to less than 2%. Generally deeper than riffles with few major flow
obstructions and low habitat complexity.
Run (migration)
Seasonal migration undertaken by fish, usually as part of their life history; for
example, spawning run of salmon, upstream migration of shad. Fishers may refer
to increased catches as a “run” of fish, a usage often independent of their migratory
behavior.
Sediment Solid material, both mineral and organic, that is in suspension in the current or
deposited on the streambed.
Sediment transport
The movement of solid particles (sediment), typically due to a combination of the
force of gravity acting on the sediment, and/or the movement of the fluid in which
the sediment is entrained.
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Abbreviation Definition
Side channel
Lateral channel with an axis of flow roughly parallel to the mainstem, which is fed by
water from the mainstem; a braid of a river with flow appreciably lower than the
main channel. Side channel habitat may exist either in well-defined secondary
(overflow) channels, or in poorly-defined watercourses flowing through partially
submerged gravel bars and islands along the margins of the mainstem.
Side slough Off-channel habitat characterization of an Overflow channel contained in the
floodplain, but disconnected from the main channel. Has clear water,
Slough
A widely used term for wetland environment in a channel or series of shallow lakes
where water is stagnant or may flow slowly on a seasonal basis. Also known as a
stream distributary or anabranch.
Spawning The depositing and fertilizing of eggs by fish and other aquatic life.
Split main channel Main channel habitat characterization where three of fewer distributed dominant
channels.
Thalweg A continuous line that defines the deepest channel of a watercourse.
Three Rivers Confluence
The confluence of the Susitna, Chulitna, and Talkeetna rivers at Susitna River Mile
(RM) 98.5 represents the downstream end of the Middle River and the upstream
end of the Upper River.
TM Technical Memorandum
Tributary A stream feeding, joining, or flowing into a larger stream (at any point along its
course or into a lake). Synonyms: feeder stream, side stream.
Tributary mouth Main channel habitat characterization of clear water areas that exist where
tributaries flow into Susitna River main channel or side channel habitats.
TWG Technical Workgroup
U.S., US United States
Upwelling
The movement of groundwater into rivers, stream, sloughs and other surface water
features. This is also called groundwater discharge and may be associated with a
gaining reach of a river or stream.
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1. INTRODUCTION
Construction and operation of the Susitna-Watana Hydroelectric Project (Project) will affect
Susitna River flows downstream of the dam; the degree of these effects will ultimately depend
on final Project design and operating characteristics. The Project will be operated in a load-
following mode. Project operations will cause seasonal, daily, and hourly changes in Susitna
River flows compared to existing conditions. The potential alteration in flows will influence
downstream resources/processes, including fish and aquatic biota and their habitats, channel
form and function including sediment transport, water quality, groundwater/surface water
interactions, ice dynamics, and riparian and wildlife communities (AEA 2011).
The potential operational flow-induced effects of the Project will be evaluated as part of the
licensing process and a Revised Study Plan (RSP) has been prepared and submitted to the
Federal Energy Regulatory Commission (FERC) that describes the Susitna-Watana Fish and
Aquatics Instream Flow Study (FA-IFS) (RSP Section 8.5) and Riparian Instream Flow Study
(R-IFS) (RSP Section 8.6) that will be conducted to characterize and evaluate these effects. The
plans include statements of objectives, descriptions of the technical framework of the studies, the
general methods that will be applied, and the study’s nexus to the Project.
Since submittal of the RSP, FERC issued a Revised Study Plan Determination Schedule (January
17, 2013) that specified deliverables of three IFS related analyses; 1) results of the open-water
flow routing model (due January 31, 2013), 2) identification of all proposed Focus Areas (FAs)
with a description of habitat units within the FAs for all aquatic studies to be implemented in the
middle Susitna River (due January 31, 2013), and 3) identification of final focus areas for 2013
middle and lower river studies (due March 1, 2013). Technical Memoranda (TM) pertaining to
each of the first two deliverables were prepared and submitted to the FERC on January 31, 2013
(R2 et al. 2013; and R2 2013a) and were subsequently presented and discussed during a
Technical Work Group (TWG) meeting on February 14, 2013, that was likewise specified in the
January 17, 2013 FERC revised schedule.
This technical memorandum pertains to the third deliverable and contains the final focus areas
and study sites for both the middle and lower river segments. The technical memorandum builds
upon the content and information presented in the middle river technical memorandum (R2
2013b), with consideration of the comments and suggestions received from the agencies and
stakeholders during the February 14, 2013 TWG meeting, to now include study sites that will be
sampled in 2013 and 2014 in the Lower River Segment. In addition, the technical memorandum
includes a separate discussion of the R-IFS Focus Area (FA) evaluation that was conducted
independent of the Fish and Aquatics IFS FA assessment presented in R2 2013b.
1.1. Background
The RSP submitted to the FERC in December 2012 contained 58 study plans that described the
objectives, locations and methods to be applied in completing the respective resource specific
studies of the Susitna River. While a number of those studies (e.g., Water Quality …,
Vegetation…, Wildlife ….) included sampling locations within all three segments of the Susitna
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River (Upper, Middle and Lower – see below)1, the IFS concerned with project operations
concentrated primarily in the Middle River Segment and deferred selection of study sites in the
Lower River Segment until results of the open water flow routing model had been completed.
Substantial information concerning the study site selection process used for the Middle River
Segment was presented in the RSP (see Section 8.5.4.2.1.2) in which a total of ten FAs were
identified and described. In terms of the FA-IFS, the representativeness of the FAs was
subsequently evaluated based on results of the habitat mapping. That analysis was presented in
the January 31, 2013 technical memorandum (R2 2013b), discussed during the TWG meeting,
and for completeness, provided as well in this technical memorandum. That meeting also
advanced the opportunity to describe the analytical framework and statistical methods that were
being applied to a separate evaluation of the FAs in terms of their applicability for the R-IFS.
That analysis has since been completed and is also summarized in this technical memorandum.
The decision reflected in the RSP to concentrate studies on the Middle River Segment was made
because Project operations related to load-following and variable flow regulation were
considered to have the greatest potential effects on that section of the river. These effects tend to
attenuate in a downstream direction as channel morphologies change, and flows change due to
tributary inflow and flow accretion. The diversity of habitat types and the information from
previous and current studies that indicate substantial fish use of a number of slough and side
channel complexes within this segment, also supported the need to develop a strong
understanding of habitat–flow response relationships in this segment.
The Revised Study Plan described the downstream boundary of the Study Area as RM 75
because existing information indicated that the hydraulic effects of the Project below the Three
Rivers Confluence are attenuated (See RSP Section 8.5.3). As described in the Revised Study
Plan, AEA reevaluated how far downstream Project operational significant effects extend based
in part upon the results of the Open-water Flow Routing Model (see RSP Section 8.5.4.3), which
was completed in Q1 2013. The results of the Open-water Flow Routing Model are consistent
with the information presented in the Pre-Application Document and information presented to
Technical Work Groups in October 2012. However, the results suggested that although the
effects of flow regulation would continue to attenuate downstream of the Three Rivers
Confluence, seasonal changes in river stage would still occur in conjunction with Project
operations 2. In addition, the hydrologic analysis indicated there would be a reduction in the
frequency of certain types of flood-flows, which shape channel morphologies, transport
sediments, and maintain riparian community structure. As a result, with consideration to the
decision criteria noted in the RSP (see page 8-23 of RSP 8.5) AEA has confirmed that studies
should be expanded in 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. Thus, in addition to describing FAs and study sites for the
Middle River Segment, this technical memorandum presents additional details concerning
studies in the Lower River Segment and includes a description and listing of study sites that will
1 The Upper River Segment represents that portion of the watershed above the Watana Dam site at RM 184, the
Middle River Segment extends from RM 184 downstream to the Three Rivers Confluence at RM 98.5, and the
Lower River Segment extends from the Three Rivers Confluence to Cook Inlet (RM 0).
2 Specifically, these seasonal changes in river stage are consistent with the information presented in the Pre-
Application Document and information presented to Technical Work Groups in October 2012.
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be evaluated in 2013 and 2014. As was noted during the TWG meeting. Information and data
collected from sites in 2013 will be reviewed in collaboration with the TWG to determine the
extent of studies and sites that warrant sampling in 2014.
1.2. Objectives
The overall objective of this technical memorandum is to describe the rationale and basis for the
final selection of the FAs and study sites, and to list those sites, that will serve as locations for
conducting detailed IFS related investigations during 2013 and 2014 in both the Middle and
Lower River segments of the Susitna River
Specific objectives include:
Review the general approach to stratification and the study site selection process used in
the FA-IFS RSP (see Section 8.5.4.2);
For the Middle River Segment:
o Describe and summarize the FA-IFS statistical analysis completed on the habitat
mapping results with respect to the ten FAs (and their habitat units)that were
initially described in the RSP (Section 8.5.4.2.1.2)
o Describe and summarize the R-IFS statistical analysis completed on the process
domains and vegetation mapping with respect to the ten FAs.
o List and describe the final FAs and study sites outside of the FAs for all IFS
related studies that will be studied in 2013 and 2014.
For the Lower River Segment:
o Discuss the rationale and criteria considered for extending the IFS related studies
into the Lower River Segment; and
o List and describe the studies and final study sites that will be evaluated in 2013
and 2014 by resource discipline.
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2. REVIEW OF RIVER STRATIFICATION AND STUDY AREA
SELECTION PROCESS
The proposed Project will affect flows in mainstem and off-channel habitats in the Susitna River
downstream of the dam site at PRM 3 187.1. In order to characterize the existing and proposed
flow regimes and potential Project-induced impacts to riverine habitats and organisms, the
Susitna River was stratified into geomorphic reaches based on channel type, gradient,
confinement, bed material and tributary confluences. As noted in Section 8.5.4.1.2 of RSP
Section 8.5, the selection of study areas or study sites represents an important aspect of all
resource related studies inasmuch as the sites or areas studied are those that will ultimately be
used for characterizing physical, geomorphological, chemical and biological resources and for
evaluating Project effects. It was therefore fundamentally important that the logic and rationale
for the selection of such areas be clearly articulated, understood, and agreed to by agencies and
licensing participants.
The RSP presented a series of steps that first described the stratification process used for the
entire river, and then discussed and evaluated various approaches to study site selection that lead
to the identification of specific FAs for intensive study within the Middle River Segment. This
process was further described in R2 2013a and discussed during the February 14, 2013 TWG
meeting. For completeness, these steps are again presented below to provide context for the
segment-specific discussion regarding site selection.
As an initial step in the selection process, the Susitna River was stratified into distinct stratum
reflective of certain geomorphic, hydrologic, and physical characteristics shared by each stratum.
The number of strata was determined based on the realization that the effects to physical
processes and aquatic resources will be resource type-, location-, and habitat-specific. For
example, at the site scale level, responses of fish habitat to changes in flow are expected to be
different in side sloughs versus mainstem versus side channel versus tributary delta versus
riparian habitats. At a broader scale, e.g., segment, it is plausible that effects to the same
mainstem habitat types will differ depending on location in the river network. In addition, there
will be a cumulative effect running down the length of the Susitna River below the dam.
Importantly, different Project operations will affect different habitats and processes differently,
both spatially and temporally. The habitat and process models will therefore need to be spatially
discrete, at potentially the site/area level, mainstem habitat type level, and segment levels, and
3 The Project River Mile (PRM) system for the Susitna River was developed to provide a consistent and accurate
method of referencing features along the Susitna River. During the 1980s, researchers often referenced features by
river mile without identifying the source map or reference system. If a feature is described by river mile (RM) or
historic river mile (HRM), then the exact location of that feature has not been verified. The use of PRMs provides a
common reference system and ensures that the location of the feature can be verified. The PRM was constructed by
digitizing the wetted width centerline of the main channel from 2011 Matanuska-Susitna Borough digital
orthophotos. Project River Mile 0.0 was established as mean low water of the Susitna River confluence at Cook
Inlet. A centerline corresponding to the channel thalweg was digitized upstream to the river source at Susitna
Glacier using data collected as part of the 2012 flow routing transect measurements. The resultant line is an ArcGIS
route feature class in which linear referencing tools may be applied. The use of RM or HRM will continue when
citing a 1980s study or where the location of the feature has not been verified. Features identified by PRM are
associated with an ArcGIS data layer and process, and signifies that the location has been verified and reproduced.
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yet able to be integrated to allow for a holistic evaluation of each alternative operational
scenario.
As noted in Section 8.5.3 of the RSP, the study area at issue with respect to Project operations
and flow regulation effects consists of two segments of the river:
Middle River Segment – Susitna River from Watana Dam site to confluence of Chulitna
and Talkeetna rivers (Three Rivers Confluence) (PRM 187.1 to PRM 102.4)
Lower River Segment – Susitna River extending below Talkeetna River to mouth (PRM
102.4 to PRM 0)
The Middle River Segment represents the section of river below the Project dam that is projected
to experience the greatest effects of flow regulation caused by Project operations. Within this
reach, the river flows from Watana Canyon into Devils Canyon, the narrowest and steepest
gradient reach on the Susitna River. The Devils Canyon constriction creates extreme hydraulic
conditions including deep plunge pools, drops, and high velocities. Downstream of Devils
Canyon, the Susitna River widens but remains essentially a single main channel with stable
islands, numerous side channels, and sloughs.
The Lower River Segment receives inflow from three other large river systems. An abrupt,
large-scale change in channel form occurs where the Chulitna and Talkeetna rivers join the
Susitna River near the town of Talkeetna in an area referred to as the Three Rivers Confluence.
The annual flow of the Chulitna River is approximately the same as the Susitna River at the
confluence, though the Chulitna contributes much more sediment than the Susitna. The
Talkeetna River also supplies substantial flow rates and sediment volumes. Farther downriver,
the Susitna River becomes notably more braided, characterized by unstable, shifting gravel bars
and shallow subchannels. The Yentna River is a large tributary to the Lower Susitna River and
supplies about 40 percent of the mean annual flow at the mouth of the Susitna River.
Geomorphic analysis of both the Middle River and Lower River segments confirmed the distinct
variations in geomorphic attributes (e.g., channel gradient, confinement, channel planform types,
and others) (see RSP Section 6.5) and resulted in the classification of the Middle River Segment
into eight geomorphic reaches and the Lower River Segment into six geomorphic reaches (see
Figures 8.5-11 and 8.5-12 of RSP Section 8.5, which for convenience have been included as
Figures 1 and 2 of this technical memorandum). These reaches were incorporated into a
hierarchical stratification system that scales from relatively broad to more narrowly defined
categories as follows:
Segment → Geomorphic Reach → Mainstem Habitat Type →
Main Channel Mesohabitat Types → Edge Habitat Types
The highest level category is termed Segment and refers to the Middle River Segment and the
Lower River Segment. The Geomorphic Reach level is next and consists of the eight reaches
(MR-1 through MR-8) for the Middle River Segment and six reaches (LR-1 through LR-6) for
the Lower River Segment (see RSP Section 6.5.4.1.2.2 and RSP Section 8.5 Table 8.5 4). The
geomorphic reach breaks were based in part on the following five factors: 1) Planform type
(single channel, island/side channel, braided); 2) Confinement (approximate extent of floodplain,
off-channel features); 3) Gradient; 4) Bed material / geology; and 5) Major river confluences.
This level is followed by Mainstem Habitat Types, which capture the same general categories
applied during the 1980s studies but includes additional sub-categories to provide a more refined
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delineation of habitat features (see RSP Section 8.5 Table 8.5 5). Major categories and sub-
categories under this level include: 1) Main Channel Habitats consisting of Main Channel, Split
Main Channel, Braided Main Channel, Side Channel; 2) Off-channel Habitats that include Side
Slough, Upland Slough, Backwater and Beaver Complexes; and 3) Tributary Habitats that
consist of the segment of the tributary influenced by mainstem flow. The next level in the
hierarchy is Main Channel and Tributary Mesohabitats, which classifies habitats into categories
of Cascades, Riffle, Pool, Run, and Glide. The mesohabitat level of classification is currently
limited to the main channel and tributary mouths for which the ability to delineate these features
is possible via aerial imagery and videography. Mesohabitat mapping in side channel and slough
habitat types will require ground surveys, planned to begin in 2013. The last level in the
classification is Edge Habitat and is intended to provide an estimate of the length of shoreline in
contact with water within each habitat unit. The amount of edge habitat within a given habitat
unit will provide an index of habitat complexity, i.e., more complex areas that consist of islands,
side channels, etc. will contain more edge habitat than uniform, single channel areas.
Overall, the goal of the stratification step was to define segments/reaches with effectively similar
characteristics where, ideally, repeated replicate sampling would result in parameter estimates
with similar statistical distributions. The stratification/classification system described above was
designed to provide sufficient partitioning of sources of variation that can be evaluated through
focused study efforts that target each of the habitat types, and from which inferences concerning
habitat–flow responses in unmeasured sites can ultimately be drawn.
2.1. Selection of Study Areas/Study Sites
In general (as noted by Bovee 1982), there are three characteristic approaches to instream flow
studies that pertain to site selection that were considered for application in the Project. These
included representative sites/areas, critical sites/areas, and randomly selected sites/areas.
2.1.1. Representative Sites
Representative sites are those where professional judgment or numerically and/or qualitatively
derived criteria are relied on to select one or more sites/areas that are considered representative
of the stratum or larger river. Representative sites typically contain all habitat types of
importance. In general, the representative site approach can be readily applied to simple, single
thread channel reaches, where the attributes that are measured are extrapolated linearly based on
stream length or area. In this case, the goal of stratification will be to identify river segments that
are relatively homogenous in terms of mesohabitat mixes, and the methods used for stratification
tend to be classification-based. This approach typically requires completing some form of
mapping up front, and using the results to select sites that encompass the range of habitat
conditions desired. The results of such habitat mapping were not available during the initial
study site/area selection, but since then, the results of the habitat mapping of the Middle River
Segment have been completed and analyzed and are reported on in Section 3.1.1.1 of this
technical memorandum.
Applicability to the Susitna–Watana Project: Yes – see Section 3 of this technical
memorandum.
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2.1.2. Critical Sites
Critical sites are those where available knowledge indicates that either (i) a sizable fraction of the
target fish population relies on that location, (ii) a particular habitat type(s) is (are) highly
important biologically, or (iii) where a particular habitat type is well known to be influenced by
flow changes in a characteristic way. For example, in the case of the Susitna River, historical
fish studies repeatedly showed the importance of certain side slough, upland slough, and side
channel areas for spawning and juvenile rearing. Critical sites or areas are typically selected
assuming that potential Project effects to other areas are secondary in terms of implications to
fish population structure, health, and size. This assumption can only really be tested if other sites
are identified that are similar looking but were not deemed critical, and sampling is performed on
those sites as well to confirm the critical nature of the sites that were identified as such.
Applicability to the Susitna–Watana Project: Yes, especially with respect to selection of side
channel/side slough/upland slough complexes that have been shown to be influenced by main
channel flows and that are biologically important.
2.1.3. Randomly Located Sites
Randomly located sites are those sites, areas, or measurement locations selected randomly from
each defined stratum or habitat type, and replicate sites or cross-sections are sampled to estimate
variance (e.g., Williams 1996; Payne et al. 2004). Site selection based on random sampling
tends to involve statistical multivariate grouping or stratification approaches, such as cluster
analysis or ordination techniques. The approach is the least subject to potential for bias, because
it relies on distinct rules and algorithms. However, the approach becomes increasingly difficult
to apply in site selection when the sites become more complex, such as is the case on the Susitna
River. In addition, the number of sites will be contingent on the variability within the universal
data set: the greater the number of clusters, the greater the potential number of sites. Strict
random sampling is therefore not likely applicable for evaluating off-channel habitats and
sloughs where the morphology of multiple channels varies substantially and in complex ways
within and across sites.
Applicability to the Susitna–Watana Project: Yes, but more appropriate with respect to main
channel mesohabitat sampling (i.e., riffle, run, glide, pool) or selection of mainstem habitat types
for Habitat Suitability Criteria (HSC) sampling.
2.1.4. Focus Areas
During the September 11, 2012, Technical Workgroup (TWG) meeting, the concept of
“intensive study areas” was introduced and discussed relative to sampling the Middle River
Segment. This concept evolved around the realization that a prerequisite to determining the
effects of Project development and operations on the Susitna River is the need to first develop an
understanding of the basic physical, chemical and ecological processes of the river, their
interrelationships, and their relationships with flow. Two general paths of investigation were
considered, 1) process and resource specific and 2) process and resource interrelated. Under the
first, process and resource specific, studies would focus on determining relationships of flow
with specific resource areas (e.g., water quality, habitat, ice, groundwater) and at specific
locations of the river without considering interdependencies of other resource areas at different
locations. Under the second, process and resource interrelated, studies would be concentrated at
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specific locations of the river that would be investigated across resource disciplines with the goal
of providing an overall understanding of interrelationships of river flow dynamics on the
physical, chemical, and biological factors that influence fish habitat.
Because the flow dynamics of the Susitna River are complex, it was reasoned that concentrating
study efforts across resource disciplines within specific locations would provide the best
opportunity for understanding flow interactions and evaluating potential Project effects and
therefore major emphasis was placed on selecting those areas, which were termed Focus Areas
(FA). However, it was also reasoned that there will be a need to collect information and data
from other locations to meet specific resource objectives. As a result, the study site/area
selection process presented in the RSP pertaining to the Middle River Segment represents a
combination of both approaches that includes sampling within specified FAs as well as sampling
outside of FAs (see Section 3.2 for discussion of sites outside of FAs).
Composition wise, the FAs contain combinations of different habitat types and features as
characterized according to the hierarchical classification system noted above that may function
and respond differently or similarly (compared to other areas) to changes in flow depending on
flow timing, magnitude, duration, etc., and their interrelationships with each other and other
resource processes. Thus, these areas would be the focus of concentrated studies across
disciplines enabling an integrated assessment of resource characteristics and processes and
providing a more meaningful understanding of resource interrelationships and how flow
regulation would influence these. This approach of concentrating study efforts within selected
areas should allow for a more comprehensive evaluation of Project effects on the different
resources, than if such features were evaluated solely in isolation resulting in a more fragmented
analysis.
As noted in the RSP and in R2 2013, the FA concept represents a combination of all three of the
study site selection methods described above, inasmuch as (1) the areas would contain habitat
types representative of other areas; (2) the areas would include certain habitat types repeatedly
used by fish and therefore can be considered “critical areas,” and (3) sampling of certain habitat
features or mesohabitat types within the areas would be best approached via random sampling.
Since the RSP, results of the habitat mapping of the Middle River Segment have been completed
which has allowed for an evaluation of the “representativeness” of the habitat types within the
ten FAs described below, compared to areas outside of the FAs. Results of that analysis are
presented in Section 3.1.1.3.
3. MIDDLE RIVER SEGMENT STUDY SITE SELECTION
3.1. Focus Areas
The RSP identified and described ten FAs that had been discussed with the TWG and were
originally proposed for detailed study within the Middle River Segment. Locations of the FAs
are depicted in Figure 1 and their specific characteristics and rationale for selection were
described in RSP Section 8.5 Table 8.5.6, which for convenience has been included as Table 1 of
this technical memorandum. Schematic photos of each of the areas were likewise depicted in
RSP 8.5 as Figures 8.5-13 through Figure 8.5-22 reproduced herein as Figures 3 through 12. The
ten FAs were intended to serve as specific geographic areas of the river that will be the subject of
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intensive investigation by multiple resource disciplines including FA-IFS, R-IFS (see Section
8.6), Groundwater (see Section 7.5), Geomorphology (see Section 6.0), Ice Processes (see
Section 7.6), Water Quality (see Section 5.0), and Fish Distribution and Abundance in the
Middle/Lower River (see RSP Section 9.6). AEA’s inter-disciplinary water resources team
developed these FAs using a systematic review of aerial imagery within each of the Geomorphic
Reaches (MR-1 through MR-8) for the entire Middle River Segment. Focus Areas were selected
within Geomorphic Reach MR-1 (one Focus Area), Geomorphic Reach MR-2 (two Focus
Areas), Geomorphic Reach MR-5 (one Focus Area), Geomorphic Reach MR-6 (four Focus
Areas), Geomorphic Reach MR-7 (one Focus Area), and Geomorphic Reach MR-8 (one Focus
Area). FAs were not selected for Geomorphic Reaches MR-3 or MR-4 due to safety
considerations related to Devils Canyon.
The FAs were those deemed representative of the major features within each geomorphic reach
and included mainstem habitat types of known biological significance (i.e., where fish have been
observed based on previous and/or contemporary studies), as well as some locations (e.g.,
Slough 17) where previous sampling revealed few/no fish. The FAs were assumed to have
included side channels, side sloughs, upland sloughs, and tributary mouths that were
representative of these habitat types in other portions of the river. This assumption has now been
evaluated based on the results of the habitat mapping. The results of that analysis were presented
in R2 (2013b), discussed during the February 14, 2013 TWG meeting and for completeness
provided in Section 3.1.1.of this technical memorandum.
Three of the FAs in Geomorphic Reach MR-6 and one in Geomorphic Reach MR-8 contain
specific habitat types that were found, during the 1980s studies, to be consistently used by
salmon for spawning and/or rearing. These areas included Slough 21, Slough 11, and Skull
Creek in Geomorphic Reach MR-6 and Whiskers Slough in Geomorphic Reach MR-8. Overall,
92 percent of the sockeye, 70 percent of the chum, and 44 percent of the slough-spawning pink
salmon were found in just these four sloughs. The FA in Geomorphic Reach MR-7 included
Slough 6A which, based on the 1980s studies provided primary juvenile rearing habitat; the FA
likewise included side channel and upland slough habitats that had been modeled in the earlier
studies. By definition, these areas of known fish use represent “critical areas” and were included
in the FAs to allow some comparisons with the 1980s data. The upper three FAs (one in
Geomorphic Reach MR-1 and two in Geomorphic Reach MR-2) were selected based on their
representativeness of the respective geomorphic reaches and the inclusion of a mix of side
channel and slough habitat types. However, there is no existing fish information on these areas
because they were not sampled in the 1980s. Nominally, the FAs range in length from 0.5 mile
to 1.9 miles (Table 1). The rationale used in the selection of each of the FAs is provided in
Table 1.
Selection criteria for the FAs considered the following:
All major habitat types (main channel, side channel, side slough, upland slough, tributary
delta) will be sampled within each geomorphic reach.
At least one (and up to three) FA(s) per geomorphic reach (excepting geomorphic reaches
associated with Devils Canyon – MR-3 and MR-4) will be studied that is/are
representative of other areas.
A replicate sampling strategy will be used for measuring habitat types within each FA,
which will include a random selection process of mesohabitat types.
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Areas that are known (based on existing and contemporary data) to be biologically
important for salmon spawning/rearing in mainstem and lateral habitats will be sampled
(i.e., critical areas).
Some areas for which little or no fish use has been documented or for which information
on fish use is lacking will also be sampled.
It is important to note that the FA concept and approach will work for the Middle River Segment
since the main channel is relatively confined. However, below the Three Rivers Confluence
where the Chulitna and Talkeetna rivers enter, the Susitna River main channel widens and
becomes heavily braided and therefore the same FA approach, which includes measurement of
the entire main channel, is not applicable in the Lower River Segment. Rather, the selection of
study sites/areas there will be more targeted to specific biologically important and representative
habitat features, such as tributary mouths, side and upland sloughs, and side channels. More
details describing the approach used in selecting study sites in the Lower River Segment are
presented in Section 4 of this technical memorandum.
3.1.1. Fish and Aquatics IFS Evaluation of Focus Areas
3.1.1.1. Habitat Mapping Analysis
Habitat mapping of the Middle River Segment of the Susitna River was completed using a
combination of geo-rectified aerial imagery (2011 Matsu Ortho Imagery at 1:8000 scale.
http://matsu.gina.alaska.edu/wms/imagery) in combination with High Definition aerial
videography that was taken of the river in August 2012 (≈ 10,000 cfs) (HDR 2013). The results
of the habitat mapping provided a spatial depiction of the distribution of habitat types and
features throughout the entire length of the Middle River Segment. Specific habitat types were
digitized using ARC GIS and lineal distances computed of each discrete habitat feature. Results
of the habitat mapping were used to evaluate the “representativeness” of the Focus Areas with
respect to other areas of the river. In this context, representativeness specifically refers to how
well habitat units within the FAs represent habitat units outside of these areas within the same
geomorphic reach.
There are multiple ways to examine or measure representativeness of the FAs but the most
valuable examination will occur after the first year of sampling when more direct information
will have been obtained of the existing habitat types from field work. However, at the current
planning stage of the study, representativeness was examined by 1) comparing the representation
of habitat types within the FAs to the representation of habitat types in the entire geomorphic
reach; 2) determining if the habitat types have been proportionately represented (focus vs. non-
focus areas); 3) determining if there was a bias in the habitat types that were selected in the FAs;
and 4) evaluating whether a random systematic approach in the selection of FAs would yield
different results than the selection process and criteria applied to the current FAs.
3.1.1.2. Habitat Data Compilation and Review
The overall objective of Middle River Segment mainstem mapping was to characterize and
classify river habitat in the mainstem from the proposed Watana Dam site to the Chulitna River
confluence. These data were used to evaluate the selection of FAs for the IFS studies (this
technical memorandum) as well as to develop a study site selection approach for the fish
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distribution and abundance studies (see Fish Distribution and Abundance Implementation Plan
for Study 9.6 [R2 2013]). The mapping effort also included tributaries extending 0.5 miles
upstream from the confluence with the mainstem. The 0.5 mile extent was used because it was
considered a conservative standard that is greater than the expected hydrologic influence of the
Project. The actual hydrologic influence is currently not known, at this time.
As a preliminary step in the analysis, the results of the GIS based habitat mapping were
presented and discussed during an IFS internal technical review meeting. Habitat mapping
generally followed the hierarchical and nested classification system developed specifically for
the Susitna River that was described above. Digital mapping results were displayed and
reviewed with technical staff who had been in the field and were familiar with channel
characteristics. The review process proceeded from the upper to lower geomorphic reaches and
resulted in a number of modifications to the habitat types. These modifications were
subsequently made and a final draft database of habitat mapping results developed. Overall, the
geo-rectified imagery in combination with aerial videography was sufficient to map the Middle
River Segment mainstem habitat to the mesohabitat level. However, the imagery was not
suitable for mapping off-channel or tributary habitats to this level; mapping of these features will
require field surveys, to be initiated in 2013.
Results of the habitat mapping as presented and summarized in HDR (2013) indicated that the
main channel habitats within the Middle River Segment of the Susitna River varied by
geomorphic reach and generally increased in complexity moving from the upper end of the
segment to downstream locations (Table 2). Mesohabitat in the main channel was generally
dominated by a mixture of run and glide habitats (Table 3). Glide and run habitats were not
distinguished from each other at this level of classification and included smooth-flowing, low
turbulence reaches as well as areas with some standing or wind waves and occasional solitary
protruding boulders. Run-glide mesohabitat dominated all reaches except MR-4, the reach
where Devils Canyon is located. Riffle habitat was most prevalent in MR-4. Riffle habitat was
lacking or only found in small amounts in the other Middle River Segment geomorphic reaches.
Side channels were predominantly glide or run, with some riffle areas in the lower reaches
(Table 3). Many side channels were not completely inundated with flowing water and so
identification of riffle or run habitat was not possible; these were classified as unidentified and
were most prevalent in MR-6.
Cascade habitat was not found within any Middle River Segment geomorphic reach. The
geomorphic reach through Devils Canyon (MR-4) contained the only rapids in the Middle River
Segment, which accounted for 38 percent of the mainstem habitat in that reach. Only 3 pools
were found in the Middle River Segment and these were also contained in MR-4 between rapids
in Devils Canyon.
Off-channel habitat was assigned to one of three habitat types observed: upland sloughs, side
sloughs, and backwaters. Upland and side sloughs were common throughout the Middle River
reaches outside of Devils Canyon and downstream of the uppermost reach at MR-1 (Table 4).
MR-5 contained some side slough habitat, MR-6 and MR-7 contained abundant side and upland
slough habitat, and MR-8 had more prevalent upland sloughs. Beaver complexes always were
associated with slough habitats and as such were not categorized as a habitat type but were noted
as a characteristic of that slough habitat unit. Beaver dams were more prevalent in upland
sloughs than in side sloughs. Beaver dams were only observed in reaches MR-6 and MR-7.
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Backwater habitat was relatively rare and found in a few areas in the lower reaches from MR-6
through MR-8. A single backwater was also delineated in both MR-2 and MR-4, but these were
very small. The greatest total area of backwater habitat was in MR-6.
The habitat associated with the confluence of tributaries with the main channel river was
documented as tributary mouth and clear water plume (Table 5). Not all tributaries that entered
the Middle River had tributary mouth habitat. Small tributaries where the vegetation line was
close to the mainstem did not fan out and create the areas classified as tributary mouth habitat.
In addition, small tributaries or tributaries that flowed into fast moving or turbulent sections of
the mainstem did not produce clear water plume habitats. Clear water plume habitats were most
prevalent in reaches MR-2 and MR-6. After the results of the habitat mapping were available,
the tributaries were further described by the possibility of being fish-bearing (e.g., no barriers)
streams. The counts of these by reach are also displayed in Table 5.
3.1.1.3. Evaluation of Representativeness – Representation and Proportionality
The habitat classifications noted above can be summarized by counts or lengths of identified
units inside and outside of FAs. However, the length of river that is included in FAs is less than
that not included in the FAs, so some scaling of counts and lengths is necessary for proportional
comparisons. A suite of scaled metrics were identified and developed that were used in a
comparative analysis of the representativeness of habitat types within and outside of FAs. These
metrics included the major habitat categories specified in the classification and consisted of
percentages or proportions of lineal distances, and densities (length per mile) (Table 6).
Values for these metrics were compared graphically by geomorphic reach. There are two bases
for comparison: 1) is each habitat type contained in the geomorphic reach represented in FAs
within the reach; and 2) is the representation proportional. The metrics cannot be statistically
compared within geomorphic reaches (focus area vs. non-focus area) because they do not
represent multiple independent random samples. Thus, there is no estimation of variance
available.
The results of this analysis indicated that the FAs have captured the majority of habitat types
present in each geomorphic reach. At the end of this technical memorandum, the proportionality
metrics are graphically displayed.
Main channel proportionality metrics are displayed graphically in Figure 13. MR-1 is all single
main channel. MR-2, MR-5, and MR-6 have a small amount of split main channel, which is not
represented within the FA. In MR-7, the split main channel is represented, but at a higher
proportion than exists in the full reach. In MR-8, the braided main channel is not represented in
the FA, and the split main channel is represented at a lesser proportion in the FA.
Side channels and sloughs proportionality metrics are displayed graphically in Figure 14. MR-1
side channels are represented. MR-2 FAs contain all habitats, with a higher portion of side
slough than the full reach. The small amounts of side slough habitat in MR-5 and MR-7are not
represented in FAs. MR-6 is well represented by FAs. MR-7 side channels and upland sloughs
are represented in FAs. In MR-8, all habitats are represented in the FAs, but there is
proportionately more side channel and side slough habitat than in the reach at large.
Beaver complex proportionality is displayed in Figure 15. Beaver habitat is represented in MR-6
and MR-7 at a higher proportionality in FAs than in the total reach.
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Backwater and tributary-related habitat proportionality is displayed in Figure 16. MR-1 does not
contain these habitat types. In MR-2, identified plumes and backwaters are not represented in
FAs. In MR-5, there is only one tributary with a mouth and plume, and it is contained in the FA.
In MR-6, all habitats are well represented. In MR-7, the single identified tributary mouth and
plume present in the reach is not represented. In MR-8, the single backwater is not in the FA,
but the tributary is in the FA.
The main channel mesohabitat comparison is shown in Figure 17. MR-1 and MR-5 are all
glide/run habitat. MR-2 has a small amount of identified riffle that is not represented in the FAs.
The other reaches are generally well represented.
3.1.1.4. Evaluation of Representativeness – Bias
Statisticians define the representativeness of samples based on the absence of bias. Statistical
bias is a consistent under- or over- estimation of a known population parameter. In this
application, bias could exist if the FAs are consistently over sampling braided main channels, for
example. For model inferences specific to habitat units, bias in proportional sampling is not a
large issue. However, if selected samples for any particular part of the program not related to the
instream flow-habitat models are used to make inference to entire geomorphic reaches, this
selection bias could result in estimation bias.
In this analysis, bias in the selection method was examined by considering the geomorphic
reaches as independent replicates of potential bias, and testing if the average bias is different
from zero using a t-test or a non-parametric equivalent. For example, if the FAs selection has
consistently under-represented upland sloughs, this analysis would highlight that result.
Results of the bias estimates are displayed in Table 7. A negative number in this table indicates
that a habitat was over-represented in the Focus Areas, and a positive number indicates that a
habitat was under-represented. There is a fairly even distribution of cases where habitat was
under-represented and over-represented across reaches. Thus, there is no strong evidence (i.e.,
no statistically significant results at an alpha level of 0.10) of bias in the habitat types that were
selected within the FAs.
3.1.1.5. Evaluation of Representativeness – Random/Systematic Approach
As a fourth comparison, a set of simulated random focus areas were selected based on a random
systematic sampling approach. These areas were selected from each geomorphic reach,
matching the number and total coverage of focus areas for each geomorphic reach. For example,
in MR-2, there are two focus areas with total length equal to 3.2 miles. For simplicity, the
simulation selected two equally sized focus areas, also totaling 3.2 miles. The process in MR-2
began with a random start and the formation of eight contiguous 1.6 mile reaches. Then one of
the four paired equally spaced reaches ((1,5),(2,6),(3,7),(4,8)) was selected at random. A similar
process was applied to the remaining five geomorphic reaches. Both the current focus area
location(s) as well as its counter parts that were randomly selected are displayed in Table 8.
The habitat features of this simulated set of focus areas was then evaluated in the same manner
as the current focus areas, and comparisons made.
The simulated selection of a set of random systematic focus areas resulted in a different balance
of habitat units. Table 9 displays the habitat proportionality metrics for project focus areas,
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simulated random focus areas, and total geomorphic reach. For some habitat types in some
geomorphic reaches, the random focus areas appear to be more representative. For example, the
main channel types (main, split, braided) in reach MR-8 are proportionally very similar in the
random focus areas and in the reach as a whole. However, in some areas the random focus areas
miss the same habitat types, as for off-channel habitats in MR-5. In other areas, the random
focus areas are less representative, as in off-channel habitats in MR-8.
Bias estimates for random focus areas are displayed in Table 10. A negative number in this table
indicates that a habitat was over-represented in the random focus areas, and a positive number
indicates that a habitat was under-represented. These results show that these random focus areas
consistently over-represented side channels and consistently under-represented riffles (with alpha
= 0.10).
The results provide a yardstick by which the representativeness of study FAs can be measured.
Although the study FAs have not perfectly represented every habitat in every geomorphic reach,
the results are similar to what would be expected with a random systematic sampling scheme.
3.1.1.6. Selection of Final Focus Areas for FA-IFS
The results of the habitat mapping and statistical analysis indicate that the ten FAs identified in
RSP Section 8.5 and presented in R2 (2013b) are generally representative of habitat types found
in other portions of the river. As a result, those ten FAs, which are listed in Table 1, should be
finalized for study in 2013 in accordance with the respective resource specific RSPs.
3.1.2. Riparian Process Domain Delineation and Evaluation of Focus Areas
The evaluation of FAs for the Middle River Segment for the R-IFS was made based on a
stratification of Riparian Process Domains as described in Riparian IFS RSP Section 8.6.3.2.
The procedures used for this and the resulting decisions that resulted in the final selection of FAs
in the Middle River Segment were made collaboratively between the Riparian Vegetation and R-
IFS leads and Dr. Robert Henszey (USFWS), and Dr. Chiska Derr (NMFS) in a riparian work
group meeting held February 21, 2013 (see Supplemental Information of U.S. Fish and Wildlife
Service/AFWFO/Anchorage filed with FERC under P-14241 [February 26, 2013] (interim
comments provided from a consensus meeting with AEA consultants, USFWS, and NMFS
regarding Riparian study focus areas). Prior to this meeting, the Riparian vegetation sampling
strategy was presented in both the Riparian Vegetation Study RSP Section 11.5, R-IFS RSP
Section 8.6 and at TWG meetings held in Anchorage, AK October 24, 2012 and February 14,
2013. This section of the technical memorandum describes the initial evaluation of
representativeness of the ten FAs for their applicability to the R-IFS.
For this evaluation, representativeness was examined by 1) comparing the representation of plant
community types within the FAs to the representation of plant community types in the entire
Riparian Process Domain (Tables 11-13) and 2) determining if the plant community types have
been proportionately represented (focus vs. Riparian Process Domain).
3.1.2.1. Initial Selection of Riparian Study Areas
As an initial step in study planning and prior to identification of any FAs, the R-IFS lead
examined the entire Middle River Segment from the Watana Dam site to the Three Rivers
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Confluence. Eight sections 1-3 miles in length, were identified that captured, upon first
examination, the variability in channel confinement (floodplain width) and channel planform
type throughout the Middle River Segment. These eight selected sections were ultimately found
to correspond to eight of the ten FAs described in the FA-IFS RSP Section 8.5 and in R2 2013a.
The two FAs that were not included in the riparian sections were those at Indian River (FA-141)
and Portage Creek (FA-151); these sites contained very little floodplain areas.
The question remained however, of whether the eight FAs identified for riparian analysis were
representative of vegetation types and abundance within the entire Middle River Segment. As a
result, a detailed quantitative analysis was completed that involved the determination of Riparian
Process Domains and vegetation typing within the entire Middle River Segment. This analysis
allowed for comparisons of vegetation type and abundance between FAs and areas outside of
FAs.
3.1.2.2. Determination of Riparian Process Domains
Delineation of Riparian Process Domains was completed using a spatially constrained cluster
analysis (Legendre and Legendre 2012) with geologic and geomorphic data gathered in ArcGIS
(see Riparian IFS RSP Section 8.6.3.2 for details). Geologic, geomorphic and floodplain
vegetation data was collected from geo-rectified aerial imagery and LiDAR digital elevation
(2011 Matsu Ortho Imagery at 1:8000 scale, http://matsu.gina.alaska.edu/wms/imagery), and
Viereck Level III classification of vegetation typing (ABR unpublished). As stated in the RSP
(8.6.3.2), process domains define specific geographic areas in which various geomorphic
processes govern habitat attributes and dynamics (Montgomery 1999). Within the mountain
river network, temporal and spatial variability of channel, ice, and sediment disturbance
processes can be classified and mapped, allowing characterization of specific riparian process
domains with similar suites of floodplain disturbance types. The riparian process domain
approach is hierarchical in structure allowing for river network stratified sampling to statistically
describe elements and processes within each process domain. The cluster delineation resulted in
four representative Middle River clusters or Riparian Process Domains (Figure 18).
3.1.2.3. Evaluation of FAs within Riparian Process Domains
Within the four defined Riparian Process Domains, the eight FAs were identified and selected
for intensive surveys of physical process, vegetation sampling (see Riparian Botanical Survey
RSP Section 11.6 for vegetation statistical sampling protocols) and riparian floodplain
interaction modeling. The FAs were those considered most representative of the Riparian
Process Domains in terms of vegetation structure and abundance, and channel / floodplain
characteristics (channel plan form, channel slope, channel confinement). Process domain
variability was assessed in terms of vegetation abundance and structure and within the selected
FAs relative to the associated Riparian Process Domain (Tables 11-13). To capture the
variability in floodplain vegetation types, and geomorphic terrains within each Riparian Process
Domain not found within the Focus Areas, satellite study sites will be surveyed outside Focus
Areas using the ITU riparian vegetation sampling protocols detailed in the Riparian Vegetation
Study RSP Section 11.6.4.
Vegetation types and geomorphic attributes were then characterized along digitized transects
located at ¼ mile intervals from the Watana Dam site (PRM 187.1) to Three Rivers Confluence
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(PRM 102.4). In the Middle River study area, a total of 340 transects were placed and aligned
perpendicular to the valley bottom axis. Each transect was segmented according to Viereck
Level III plant community type and channel type. Lineal distances were computed for each
discrete vegetation community or water feature. Segments attributed to active channel types
(e.g., Main Channel, Side Channel, Split Main Channel, Braided Main Channel) and segments
attributed to each plant community type were summed for each transect. Determinations of
active channel vs. off-channel geomorphic features were consistent with definitions provided for
Geomorphology Study (HDR 2013). The transect data describes the spatial distribution and
abundance of plant communities along the entire length of the Middle River Segment.
Summary tables (Tables 11-13) were subsequently developed of Level III vegetation types, and
type abundance for: (1) each of the three riparian process domains (Devils Canyon was excluded
leaving three domains); (2) each of the eight FAs; and (3) comparisons between total Riparian
Process Domain vegetation type and abundance within the FAs with those found in each domain.
3.1.2.4. Selection of Final Focus Areas for R-IFS
Overall, the analysis demonstrated that the vegetation types and abundance found within the
eight FAs provides a good representation of the types and relative abundance of vegetation found
within the respective Riparian Process Domains. As a result, these eight FAs were given further
consideration by the riparian study team. This team, which included representatives from the
USFWS (B. Henzsey) and NMFS (C. Derr), reviewed each of the eight FAs and selected five for
detailed study. The three not selected (FA-184, FA-171, and FA-144) were found to be lacking
in one or more characteristics including floodplain vegetation, floodplain terrain complexity, or
wetland complexity (see Table 14). The final list of FAs that will be sampled for R-IFS
investigations is listed in Table 15 and depicted in Figure 18.
3.2. Sites Outside of the Focus Areas
As noted in the RSP Section 8.5 and R2 (2013b), the boundaries of the FAs do not limit the
geographic extent of other studies, as many other study sites and areas already have been or will
be located as part of resource specific investigations. Indeed, other resource studies have
identified study sites outside of FAs as necessary to achieve specific resource study goals and
objectives (see Fisheries (RSP Section 9.6, 9.8, and 9.9), Groundwater (RSP Section 7.5),
Geomorphology (RSP Section 6.0), Ice Processes (RSP Section 7.6), and Water Quality (RSP
Section 5.0). Fisheries studies for example, have and will be conducted in multiple locations
both within and outside of FAs as a means to fully characterize fish distributions in the Middle
and Lower River segments (see Fish Distribution and Abundance Implementation Plan for Study
9.6 (R2 2013a). In addition, the salmon escapement studies will be monitoring fish movements
within a 184-mile section of the river extending from PRM 26 upstream to Kosina Creek at PRM
209.1, and further upstream as necessary. In addition, 17 fixed telemetry stations will be
installed within a mixture of tributaries and slough habitats at locations throughout the entire
length of the river. Water quality studies will likewise occur at locations within and outside of
FAs. A total of 39 water quality monitoring stations have been identified that extend from PRM
20 to PRM 235.1. These sites will be used for collection of baseline water quality data. In
addition, water quality sampling will be conducted in selected FAs to provide a more detailed
characterization of water quality characteristics in those areas as they relate to fish productivity
and main channel flow conditions (see RSP Section 5). Fluvial geomorphology studies
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involving sediment transport and large woody debris distribution likewise include areas both
within and outside of FAs, as do the Ice Processes studies. The Ice Processes studies include
time-lapse photography at more than 25 sites in the river extending from PRM 15.1 to PRM 226,
as well as winter discharge measurements at selected cross-sections, and winter field studies of
FAs as a means to understand how winter conditions affect fish habitats and geomorphology.
In terms of the FA-IFS, there are a total of 80 cross-sectional transects in the Middle River
Segment and 8 transects in the Lower River Segment that have been established and flow data
collected to support development of the open-water flow routing model (see Open-water Flow
Routing Model Results technical memorandum [R2 et al. 2013], and RSP Section 8.5.4.3 and
Table 8.5-7 reproduced herein as Table 16). These transects were primarily located across single
thread sections of the river; however, some do extend across more complex sections. In most
cases, two to three sets of flow measurements have been made at each transect. The resulting
data sets can be used, at a minimum, for evaluating velocity-depth distributions across the
channel that can be related to biologically relevant criteria associated with various life stage
requirements (e.g., spawning, adult holding, juvenile rearing). In many cases (pending review of
the cross-sectional data), it should be possible to develop actual habitat-flow relationships
following a 1-D PHABSIM type analysis (see RSP Section 8.5.4.6). The cross-sectional
transects represent an important dataset that can be used to characterize habitat-flow response
characteristics of the main channel of the Susitna River. These types of data were never
collected during the 1980s studies and no main channel habitat-flow relationships were
developed. Importantly, now that the main channel habitat mapping is completed (see Section
6), the transect locations have been assigned to specific mainstem habitat types (main channel,
side channel, split channel, etc.) and main channel mesohabitat types (e.g., riffle, run, glide,
pool) and can be randomly selected for analysis. These additional transects may also be useful
for extrapolating results/relationships from measured to unmeasured sites (see RSP Section
8.5.4.7).
For the R-IFS, in addition to the five FAs, a quantitative determination will be conducted prior to
summer field operations to select additional vegetation sample sites (i.e., satellite sites),
throughout each of the three Middle River Process domains representative of herbaceous plant
communities. This was specifically requested by Dr. Robert Henszey as noted in the working
group meeting summary (see Supplemental Information of U.S. Fish and Wildlife
Service/AFWFO/Anchorage filed with FERC under P-14241 [February 26, 2013] (interim
comments provided from a consensus meeting with AEA consultants, USFWS, and NMFS
regarding Riparian study focus areas).
3.3. Final Listing of Focus Areas and Study Sites for Middle River
Segment
The results of the habitat mapping analysis completed for the FA-IFS and the process domain
analysis completed for the R-IFS have provided insight into the types and distributions of
mainstem habitats and the variability of process domains and vegetative community types within
the Middle River Segment of the Susitna River.
With respect to the FA-IFS, the results of the habitat mapping and statistical analysis indicate
that the ten FAs identified in RSP Section 8.5 are generally representative of habitat types found
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in other portions of the river. As a result, those ten FAs, which are listed in Table 1, have been
selected for study in 2013 in accordance with the respective resource specific RSPs.
However, according to the existing habitat mapping framework and results, there are some
habitat types within individual geomorphic reaches that were not represented in the reach-
specific FAs or captured in the existing transects (Table 17). These habitats were reviewed and
the following considerations applied in evaluating the need for adding supplemental sites in 2013
to capture those habitats:
Whether on-the-ground detailed habitat mapping that will occur within FAs in 2013 may
identify additional habitat features (e.g., plumes and backwaters) negating the need to add
supplemental sites for these currently “missing” habitat types;
Whether the “missing” habitat types are similar enough to habitat types in FAs within
adjacent geomorphic reaches (e.g., split main channel in MR-2 may be similar to split
main channel in MR-1) to negate the need for adding supplemental sites, noting that the
2013 studies will help evaluate this; and
There will be time in 2014 to add supplemental transects to biologically important habitat
types that are not found to be represented in the FAs even after the 2013 on-the-ground
detailed habitat mapping.
The habitats present within each reach but located outside of FAs were examined and evaluated
relative to the above three considerations, as follows:
1. MR-2 Split Main Channel and Backwater
Figure 19 shows the sole complex with split main channel and the sole backwater
identified by habitat mapping in reach MR-2. A supplemental cross-section could be
added to this complex. However, both of these features may be represented adequately
by similar features in other reaches. Importantly, the only backwater identified by the
habitat mapping is very close to a protected raptor nesting area, which is likely to impede
additional sampling in that area during some seasons. However, if these habitats are not
found to be easily represented by other features, based on detailed habitat studies
completed in 2013, then supplemental cross-sections will be added and the backwater
habitat sampled in 2014.
2. MR-5 Split Main Channel and Side Slough
Figure 19 shows the only split main channel and side slough habitat that exists in
Geomorphic Reach MR-5, which is downstream of FA-151. However, results of the
detailed habitat studies completed in 2013 may reveal that these features are represented
by similar features in MR-6. If not, then supplemental cross-sections will be added and
the backwater habitat sampled in 2014.
3. MR-7 Tributary Mouth and Plume
Figure 19 shows the only tributary mouths and plume in MR-7 identified by the habitat
mapping. One of the tributaries, Lane Creek, has two associated mouth areas, as it splits
into two branches prior to entering the main channel. The plume is associated with Lane
Creek. If these features are found to be important habitats that cannot be represented by
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similar features in other reaches after 2013 detailed habitat studies, then supplemental
cross-sections will be added by Lane Creek to capture mouth and plume habitat in 2014.
4. MR-8 Backwater
Figure 19 depicts one of very few backwater habitats in MR-8. This feature appears to be
relatively unique to this area of the river, and therefore supplemental cross-sections will
be added in 2013 to capture this backwater habitat.
Results of the R-IFS analysis likewise indicated that the variability of the process domains and
vegetative community types are generally captured within the boundaries of the geomorphic
reaches and can be sufficiently characterized within a subset of the ten FAs. This subset entails
five FAs including the lower four: FA-104, FA-115, FA-128, and FA-138, as well as one FA
above Devils Canyon, FA-173. Table 15 depicts the final listing of FAs selected for the R-IFS.
The results of the analysis demonstrate that there is sufficient similarity in process domains and
vegetation types within the other FAs to one or more of the five FAs that there is no need for
specific R-IFS studies in those areas. The results of the R-IFS analysis also did not show the
need to add any supplemental sites or FAs in the Middle River Segment.
Overall, the ten FAs, coupled with identified additional sampling sites (i.e., cross-sections) that
have been established outside of the FAs, the study sites outside of the FAs that have been
identified as part of other resource studies, and supplemental sites as determined will be needed
in 2013 (e.g., the one MR-8 Backwater habitat type) and 2014 (based on results of 2013 studies),
will collectively provide a comprehensive and spatially expansive array of study areas and sites
within the Middle River Segment of the Susitna River.
However, this does not mean that refinements to the list are not possible. As was noted in the
RSP, results of the 2013 studies will be reviewed and evaluated, and may result in some
refinements to existing study sites/areas and/or establishment of supplemental sites that target
specific habitat-flow relationship types. For example, the scaling up/expansion of flow – habitat
relationships derived from measured to unmeasured sites or locations within the river may
require measurement of certain flow attributes (e.g., determination of the relationships of main
channel flow to side channel and side slough breaching flows; defining areas of turbid/non-turbid
waters; defining areas of groundwater upwelling) at unmeasured areas. In addition, the results of
detailed on-the-ground habitat studies may likewise reveal the need to sample additional habitat
types that were not directly captured in the FAs (e.g., habitat types in MR-2, MR-5, and MR-7
noted above). The Final FAs and study sites remain subject to refinement based on results of
2013 investigations and study needs.
Finally, during the February 14 TWG meeting, AEA received feedback regarding potentially
moving the location of a MR-2 FA to MR-7. The results of both the FA-IFS and R-IFS FA
analysis clearly indicate that the selected areas listed in Tables 1 and 15 are representative of
other areas in the Middle River Segment and hence are appropriate and sufficient for detailed
study. However, AEA does not oppose making the suggested relocation of a MR-2 FA to MR-7
(or other possible adjustments to existing FA locations) prior to the initiation of the 2013 field
studies so long as there is sufficient justification for such relocation and the resulting FA remains
representative of other areas in the Middle River Segment.
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FERC Project No. 14241 Page 20 March 2013
4. STUDY SITES IDENTIFIED IN THE LOWER RIVER SEGMENT
4.1. Rationale for Lower River Studies
The Revised Study Plan described the downstream boundary of the Study Area as RM 75
because existing information indicated that the hydraulic effects of the Project below the Three
Rivers Confluence are attenuated (see RSP Section 8.5.3). As described in the Revised Study
Plan, AEA reevaluated how far downstream Project effects extend based in part upon the results
of the Open-water Flow Routing Model (see RSP Section 8.5.4.3),which was completed in Q1
2013 (R2 et al. 2013). The results of the Open-water Flow Routing Model are consistent with
the information presented in the Pre-Application Document and information presented to
Technical Work Groups in October 2012. However, the results suggested that although the
effects of flow regulation would continue to attenuate downstream of the Three Rivers
Confluence, seasonal changes in river stage would still occur in conjunction with project
operations.[1]
As noted in RSP Section 8.5.3, the extent of studies conducted in the Lower River Segment will
be based upon consideration of the following six criteria.
Criteria 1 - Magnitude of daily stage change due to load-following operations relative to
the range of variability for a given location and time under existing conditions (i.e.,
unregulated flows);
o Results of the Open Water Flow routing model were presented in R2 et al. (2013)
and discussed during the February 14, 2013 TWG meeting. Results indicated that
pre- versus post-Project stage changes varied by location and time and ranged at
Gold Creek (Middle River Segment) from an increase in daily average water level
of up to 2 to 3 feet in the winter and a reduction of daily average water level of as
much as 5 feet in the summer during high natural flow conditions (See Figures
5.4-2 and 5.4-3 of R2 et al. 2013). More typically the change would be about 3
feet in the summer. The predicted change in stage in the upper portion of the
Lower River Segment at Sunshine ranged from an increase in daily average water
level of up to 1 to 2 feet in the winter and a reduction in water level of as much as
3 feet in the summer during high flow conditions (Figures 5.4-4 and 5.4-5 (R2 et
al. 2013). Daily and hourly changes in stage during the summer period at
Sunshine were predicted to range from 0.6 to 0.8 feet, but accurate estimates for
the winter period are contingent on completion of the winter flow routing model.
Criteria 2 - Magnitude of monthly and seasonal stage change under Project operations
relative to the range of variability under unregulated flow conditions;
o Results of a comparative hydrologic analysis considering existing and with-
Project operations was completed by Tetra Tech and presented and discussed
during the February 14, 2013 TWG meeting (Tetra Tech 2013). These results
were based on a 61 year extended discharge record that had been developed by
the USGS. Comparisons were made of monthly flows and annual flows under
[1] Specifically, these seasonal changes in river stage are consistent with the information presented in the Pre-
Application Document and information presented to Technical Work Groups in October 2012.
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FERC Project No. 14241 Page 21 March 2013
pre-Project and a maximum load following scenario. Results showed substantial
changes in seasonal flows during both the summer (Project operational flows
were lower) and winter (project operational flow were higher) periods (as had
been noted in the Pre-Application Document) with summer changes most
pronounced in the upper portions of the river (pre- and post-Project flows at Gold
Creek in July: 20,000 cfs versus 6,980 cfs; and at Susitna Station 122,000 cfs
versus 108,000 cfs) while winter changes were evident throughout the entire river
length (pre-post flows at Gold Creek in January: 1,280 cfs versus 8,840 cfs; and at
Susitna Station – 7,910 cfs versus 15,500 cfs). Results of flow duration analysis
demonstrated the shifts in flow magnitudes that would occur with Project
operations.
o Flood frequency analysis likewise indicated there would be changes in return
periods of specific flood magnitudes. For example at Gold Creek, a two-year
flood event (i.e., a flood that occurs on average once every two years) of 43,700
cfs would, under maximum load following operations occur once every 12 years.
Likewise, at Susitna Station, a two year flood of 170,300 cfs would occur once in
every five years.
o Further hydrologic analysis will be completed as part of an IHA analysis
described in RSP Section 8.5.4.4.1.3.
Criteria 3 - Changes in surface area (as estimated from relationships derived from
LiDAR and comparative evaluations of habitat unit area depicted in aerial digital
imagery under different flow conditions) due to Project operations;
o The analysis of LiDAR data (Criteria 3) is still ongoing and results were not
available to make quantitative estimates of Project induced areal changes.
However, inferences of surface areas can be drawn from the previous work of
R&M Consultants and Trihey and Associates (1985). Review of that document
and the analysis presented indicates that changes in surface area with flows can be
pronounced depending upon the range of flows considered, as well as specific
habitat types (e.g., side channel, side sloughs, etc.). As R&M Consultants and
Trihey and Associates (1985) noted, surface area responses are a function of
streamflow and channel geometry. Examples of flow responses to wetted surface
areas for different locations in the Lower River Segment are found in Figures 3-1
through 3-4 of R&M Consultants and Trihey and Associates (1985). Inspection
of those relationships indicates that surface areas of certain types of habitats can
be quite sensitive to changes in main channel flows. Additional analysis of these
data is in progress and will be available in Tetra Tech (2013b).
Criteria 4 - Anticipated changes in flow and stage to Lower River off-channel habitats;
o The flow and stage changes indicated by the results of the flow routing model and
hydrologic analysis cannot be directly related to off-channel habitats since results
of the LiDAR analysis has not been completed and detailed bed topography of
specific areas has not yet been acquired. However, reasonable inferences can be
made based on the timing, magnitude, and duration of flow and stage changes
associated with the proposed Project operations on different types of lateral
habitats. For example, it is reasonable to assume that some of the lateral habitats
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FERC Project No. 14241 Page 22 March 2013
inundated under pre-Project flow conditions could become partially dewatered or
disconnected from the main channel under summer time Project operations due to
reductions in flow and stage. Conversely under winter time operations, habitats
that may normally be disconnected from the main channel and operate as clear
water side slough habitats may become connected due to flow increases and
breaching at the head end of the channel resulting in turbid water conditions.
Criteria 5 - Anticipated Project effects resulting from changes in flow, stage and surface
area on habitat use and function, and fish distribution (based on historical and current
information concerning fish distribution and use) by geomorphic reaches in the Lower
River Segment;
o Based on the anticipated changes in stage and flows in the Lower River Segment,
it is reasonable to assume there would likely be some effects on fish habitat and
fish distribution, resulting from Project operations. However, the magnitude and
extent of such effects cannot be defined without further study.
Criteria 6 - Initial assessment of potential changes in channel morphology of the Lower
River (see Section 6.5.4.6) based on Project-related changes to hydrology and sediment
supply in the Lower River.
o The initial assessment of potential channel changes was performed and reported
in three technical memoranda developed in the 2012 Geomorphology Study:
Stream Flow Assessment (Tetra Tech 2013a), Development of Sediment-transport
Relationships and an Initial Sediment Balance for the Middle and Lower Susitna
River Segments (Tetra Tech 2013b), and Reconnaissance Level Assessment of
Potential Channel Change in the Lower Susitna River Segment (Tetra Tech
2013c). The conclusions from each are summarized below.
Stream Flow Assessment (Tetra Tech 2013a): The primary basis for identifying
the need to continue the 1-D bed evolution modeling effort below the initially
proposed downstream extent was based on interpretation of the results of the
potential changes in hydrology identified in this technical memorandum. A
comparison of the annual peak flow frequency results between the existing
conditions and the Maximum Load Following Operations Scenario 1 indicates an
appreciable reduction in flows in the 1.5- to 5-year range of recurrence intervals
in the Lower River. Discharges in the range of the 1.5- to 5-year peaks are often
representative of the channel forming or effective discharge to which the bankfull
channel capacity adjusts in streams such as the Lower River Segment that have
mobile bed material and a substantial sediment supply (Wolman and Miller 1960,
Wolman and Gerson 1978, Williams 1978, Andrews 1980). For the 2-year event,
the reduction at Sunshine and Susitna Station were estimated at 24 percent and 17
percent, respectively. Numerous researchers have identified hydraulic geometry
relationships (i.e., relationships between channel dimensions and discharge) that
clearly demonstrate this linkage (Leopold and Maddock 1953, Langbein 1964,
Emmett 1972, Parker 1979, Andrews 1984, Hey and Thorne 1986, Julien and
Wargadalam 1995). The channel width is typically proportional to about the
square-root of the discharge; thus, the indicated reductions in 2-year discharge
suggest that the channel could narrow by slightly more than 10 percent in the
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FERC Project No. 14241 Page 23 March 2013
portion of the Lower River segment below Sunshine, and less than 10 percent
downstream from the Yentna River confluence. The narrowing could occur
through a combination of vegetation encroachment and sediment deposition along
the margins of the channel and by expansion of the mid-channel islands. Since
the channel margins, including the side sloughs are key habitat units, changes in
these areas could have implications to habitat.
Development of Sediment-Transport Relationships and an Initial Sediment
Balance for the Middle and Lower Susitna River Segments (Tetra Tech 2013b):
Results from this technical memorandum indicated that the portion of the Lower
River Segment below Sunshine is aggradational under pre-Project conditions, and
it would likely remain aggradational under Maximum Load Following OS-1
conditions, although the magnitude of the aggradational tendency would be
somewhat reduced. The sediment balance results are inconclusive as to whether
significant channel change would occur as a result of the Project. More accurate
quantification of this change under Project conditions is necessary to provide a
basis for understanding the potential implications to the change in sediment
balance to both channel form and instream and channel-margin habitat. Extension
of the 1-D bed evolution model downstream to Susitna Station will help provide
this understanding.
Reconnaissance Level Assessment of Potential Channel Change in the Lower
Susitna River Segment (Tetra Tech 2013c): In this technical memorandum, the
application of the Grant et al. (2003) conceptual model of channel change
suggested that the potential for significant change in the Lower River Segment
downstream from Sunshine is indeterminate; thus, it cannot be concluded with
certainty that the impacts of the Project would be acceptably small. The results of
the model indicated that the portion of the Lower River Segment above Sunshine
will continue to be aggradational with respect to the gravel load, but it is likely to
see little impact related to sand transport. Although these results are not extreme,
the model output suggests that the portion of the Lower River Segment could tend
toward degradation and channel narrowing.
As a result, AEA has confirmed that studies should be expanded in 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.
This technical memorandum presents additional details concerning studies in the Lower River
Segment and includes a description and listing of study sites that will be evaluated in 2013 and
2014. As was noted during the TWG meeting, the number and locations of sites may ultimately
vary depending upon accessibility and safety considerations.
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FERC Project No. 14241 Page 24 March 2013
4.2. Resource Specific Studies and Study Sites in Lower River
Segment
4.2.1. Fish and Aquatics Instream Flow Study
The Lower River segment consists of approximately 102.4 miles of river between the Three
Rivers Confluence and Cook Inlet (Figure 20). For several miles downstream of the Three
Rivers Confluence, the Susitna River becomes braided, characterized by unstable, shifting gravel
bars and shallow subchannels. For the remainder of its course to Cook Inlet, the Susitna River
alternates between single channel, braided, and meandering plan forms with multiple side
channels and sloughs. Major tributaries drain the western Talkeetna Mountains (the Talkeetna
River, Montana Creek, Willow Creek, and Kashwitna River), the Susitna lowlands (Deshka
River), and the Alaska Range (Yentna River). The Yentna River is the largest tributary in the
Lower River Segment, supplying about 40 percent of the mean annual flow of the Susitna River
at its mouth.
Macrohabitat types in the Lower River Segment include main channel, side channels and
sloughs, backwater, and tributary mouths (Tetra Tech 2013a). In comparison to the Middle
River, the Lower River channel exhibits much lower gradient with a wider floodplain containing
numerous subchannels. Focus Areas were identified in the Middle River to describe existing
conditions and the response of habitats to proposed Project releases. Modeling of the Middle
River FAs will integrate studies of fisheries, geomorphology, groundwater, riparian, ice
processes and water quality. The Middle River FAs range from 0.5 to 1.8 miles in length and
data will be collected to develop digital terrain models of each Focus Area. Hydraulic conditions
within these FAs will be based on 2-D modeling that will be integrated into PHABSIM-type
analyses of potential fish habitat. Due to the size and complexity of the Lower River Segment
channel, a similar 2-D modeling of FAs is not feasible.
As described in RSP Section 8.5.4.2.1.2: Selection of Study Areas/Study Sites, instream flow
study sites are generally identified following representative, critical, and/or random approaches.
Representative or random site selection approaches generally require comprehensive habitat
mapping results and selection of critical sites generally requires available knowledge of
biologically important habitats. Study areas were tentatively identified by AEA’s inter-
disciplinary team including representatives from geomorphology, instream flow-fish, instream
flow-riparian, and groundwater. One area was selected in each of the geomorphic reaches LR-1
and LR-2 to describe the mix of thalweg channel, major subchannels, alluvial island complexes,
side channels and sloughs observed in aerial photos of the Lower River Segment channel. The
area around Trapper Creek near PRM 94.5 was selected as representative of the habitat types in
LR-1 (Figure 21), and the area around Caswell Creek near PRM 67 was selected as
representative of habitat types in LR-2 (Figure 22).
Fish habitats in the Lower River Segment will be modeled using a 1-D approach involving
transects selected to represent major habitat types within each geomorphic reach. Data collection
and modeling efforts will be conducted in LR-1 and LR-2 in 2013. Data collection and modeling
efforts will be evaluated in Q4 2013 to identify the number, location and type of habitat
modeling efforts to be conducted in the Lower River Segment in 2014. The size and complexity
of the Lower River Segment channel presents significant challenges to data collection and
modeling efforts and the results of the 2013 efforts will guide additional efforts in 2014.
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In addition to describing representative habitat types in LR-1 and LR-2, tributary mouths were
identified as potential critical sites. During the 1980s, the primary salmon spawning areas within
the Lower River Segment appeared to be clearwater tributaries (R&M Consultants, Inc. and
Trihey & Associates 1985b); although 1980s sampling limitations may have overlooked some
mainstem salmon spawning. Low velocity backwater areas near tributary mouths were used as
holding areas by adult salmon during upstream migration into the tributaries, and tributary
mouths became a major component of Lower River studies during the 1980s. In addition to
evaluating potential effects of Project flow releases on adult salmon holding areas at Lower
River Segment tributary mouths, 1980s studies included analyses of salmon access into
tributaries and the geomorphic stability of tributary mouths. Thirteen Lower River Segment
tributary mouths were selected for study in the 1980s (Table 18) (R&M Consultants, Inc. and
Trihey & Associates 1985b).
Recent biological studies appear to support the continued importance of Lower River Segment
tributary mouths as salmonid habitat. During 2012, habitats in LR-1 and LR-2 were
opportunistically surveyed to collect habitat suitability criteria (HSC). Of the 69 HSC
observations of adult, juvenile, and fry life stages, 42 percent were located in tributary mouth
macrohabitats.
Of the thirteen tributary mouths studied in the 1980s, five were selected for study during 2013.
Trapper Creek and Birch Creek are located in the vicinity of the LR-1 study area, and Sheep
Creek and Caswell Creek are located in the vicinity of the LR-2 study area. The Deshka River
was identified as an important adult salmon holding area during the February 14, 2013 TWG
meeting and the Deshka River mouth was added to the list of 2013 study areas. The mouth of
the Kashwitna River is located near the LR-2 study area, but it was not selected for study in 2013
because it does not appear to be heavily influenced by potential Project flow releases (Table 18).
In terms of sampling methods, approximately ten transects will be located at each selected
tributary mouth extending from the clearwater plume at the tributary confluence upstream into
the tributary extending above the extent of backwater influence from the main channel. In
addition to evaluating the effects of Project flow releases on salmon habitat, channel and
hydraulic data collected at the tributary mouths can be used to evaluate the effects of Project
flow releases on boat access into tributaries and use of tributary mouths by recreational anglers.
During 2013, the mouths of the tributaries not selected for measurement and modeling will be
reconnoitered by representatives of the instream flow–fish, geomorphology and water quality
disciplines to evaluate additional modeling efforts in 2014.
Input to the Lower River Segment hydraulic and fish habitat models will include cross-section
profiles of each transect measured between high water end points. At least one water surface
elevation per transect, and associated channel and mainstem discharge will be needed along with
substrate and cover descriptions. The velocity distribution along each study transect will be
measured to describe the mean column velocity in each wetted cell in the study transect. Data
collection efforts to support the 1-D instream flow fish habitat model will be coordinated with
geomorphology and instream flow-riparian study efforts. Those studies will also need data
collected along transects and where feasible, instream flow transects will be co-located with
geomorphology and instream flow-riparian transects. Data needs for both instream flow fish
habitat and geomorphology include:
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FERC Project No. 14241 Page 26 March 2013
Stage recorders installed at key main channel and side channel locations to provide water
surface elevations to calibrate the open-water flow routing model and the 1-D PHABSIM
models.
Cross-section profiles at approximately ten transects on the lower portion of each of the
five selected tributaries. The number of transects at individual tributaries will depend on
channel complexity and the extent of mainstem backwater influence. Where feasible,
instream flow fish habitat transects will be co-located with geomorphology and instream
flow-riparian transects.
Thalweg profile for each of the five selected tributaries from the confluence with the
main channel or side channel upstream to a location above the backwater influence
during high flow conditions.
Stage recorders will be installed at the lower end of each tributary in the backwater area
and on each tributary upstream of the extent of backwater. Stage readings will be
recorded at 15-minute intervals during portions of all four seasons for a period sufficient
to develop annual hourly inflow records.
Flow measurements will be collected near the stage recorders upstream of the backwater
area to establish rating curves on each of the five tributaries.
Data collected at tributary mouths will be used to develop a HEC-RAS model to describe
the relationship between mainstem flow and tributary water surface elevations.
Water surface elevations will be modeled using a stage:discharge relationship (rating curve) to
calculate water surface elevations at each transect. The basic computational procedure will be to
perform a log-log regression between observed stage and discharge pairs at each transect. The
resulting regression equation will then be used to estimate water surface elevations at all flows of
interest. In the stage:discharge relationship and its simulation, each transect is treated as
independent. Data input include water surface elevations and three or more associated discharge
measurements. If at least three stage:discharge data pairs are not available, water surface
elevations will be calculated using Manning's equation.
Velocity distributions within a transect (i.e., the mean column velocity in each wetted cell in a
study transect at each simulation discharge) will be simulated over the range of target discharges.
Input to the model include at least one set of measured velocities per transect that act as a
template to distribute velocities across a channel by solving for the 'n' in Manning's equation.
The channel is divided into cells and the velocity calculated for each of these cells. The usual
practice is to use one set of velocities as a template for simulating velocities for a particular
range of discharges (USGS 2012). When more than one set of velocity measurements is
available, a commensurate number of flow ranges can be simulated with different velocity
templates. However, accuracy at a measured calibration flow may be affected when trying to
achieve a better fit over a full range of calibration flows.
In addition to measurement and modeling of macrohabitat types in Lower River geomorphic
reaches LR-1 and LR-2, HSC criteria will be collected from representative habitat types at each
of the five tributary mouths. A minimum of three samples will be selected from each of the
habitat types within each tributary sampling area. HSC site selection will require the results of
habitat mapping of the Lower River Segment. In addition to technical considerations, access and
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FERC Project No. 14241 Page 27 March 2013
safety will be key non-technical attributes for site selection for all studies conducted in the
Lower River Segment.
In support of the evaluation of channel change in the Lower River, geomorphic features in the
Lower River were mapped as polygons from the Three Rivers Confluence to Cook Inlet (Tetra
Tech 2013b). The results of geomorphic feature mapping provide a spatial depiction of the
distribution of channel features throughout the entire length of the Lower River Segment.
Results of the geomorphic mapping will be used to evaluate the “representativeness” of the
Lower River study areas with respect to other areas of the river. In this context,
representativeness specifically refers to how well habitat units within selected study areas
represent channel features outside of these areas but within the same geomorphic reach. An
evaluation of the representativeness of the Lower River study areas will occur in Q4 2013 after
the first year of sampling. By fall 2013, information will be available on the feasibility of
measuring and modeling various channel and hydraulic conditions in the Lower River.
Information on the distribution of fish among channel features and habitat use will also be used
to identify additional data needs to evaluate Project effects on Lower River habitats. The
location, number, and type of additional physical and hydraulic data needed to describe Lower
River habitats will be confirmed in Q1 2014 prior to the 2014 open-water field data collection
period.
4.2.2. Riparian Instream Flow Study
Upon determination that the Lower River Segment would be studied in the 2013 field season, a
riparian vegetation sampling approach was developed with R-IFS, Riparian Vegetation Study,
Geomorphology Study, and Groundwater Study leads and representatives of USFWS and
NMFS. It was agreed that the Lower River Segment sampling approach would include:
1. characterization of both floodplain vegetation type and diversity,
2. broad spatial scope of the Lower River,
3. utilization of Geomorphology Study 1-D sediment transport and flow routing modeling
transects, and
4. selective installation of groundwater wells.
It was further agreed that vegetation sampling would be conducted along floodplain wide
transects selected to represent Geomorphic Reaches LR-1 to LR-5 extending down river to PRM
29.5 (Figure 20). The utilization of the Geomorphology Study transects will allow for modeling
of surface water regime characteristics associated with floodplain vegetation types sampled
along each transect. In addition to surface water modeling selective sites, groundwater wells,
two per transect, will be installed to characterize groundwater floodplain vegetation type regimes
within the Lower River Segment. This riparian sampling approach, capitalizing on the
Geomorphology sediment transport and flow routing studies, will provide a broad scale sample
of the Lower River Segment floodplain vegetation types, surface water regimes associated with
those types and will characterize vegetation type groundwater regimes. These data will be
utilized to develop final 2014 riparian vegetation sampling strategy and sampling design.
The riparian sample transect locations in the Lower River Segment are presented and described
in Table 19 and depicted in Figure 20.
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4.2.3. Groundwater
The Groundwater Study (RSP Section 7.5) has several study objectives involving the Lower
River Segment of the Susitna River. Study objectives include data and information synthesis
(RSP Section 7.5.4.1.1) which will provide a review of pertinent reports, papers, state and federal
database reviews for groundwater wells and springs site information from historical and more
recent information. This information will help determine the regional context for geohydrologic
units within the larger watershed groundwater flow system. The regional understanding of
significant groundwater upwelling areas in the lower reaches will be addressed in study efforts
described in RSP Section 7.5.4.3. This study effort will use Ice Processes Study information on
open leads during winter conditions (RSP Section 7.6.4.1), existing aerial photography, winter
discharge measurements, and other field observations from hydrology programs to characterize
the changes in baseflow conditions associated with groundwater upwelling in the portion of the
study area above PRM 30.
The Groundwater Study in the Lower River Segment will characterize groundwater conditions
associated with five cross-sections that will serve multi-disciplinary purposes, one located in
each geomorphologic reach above PRM 30 (Figure 18). These cross-sections will be used across
resource disciplines (R-IFS, FA-IFS, and Geomorphology) and will result in the collection of a
coordinated set of data that can be used for evaluating Project operational effects, including
effects in the winter, on multiple resources. For groundwater studies, two shallow wells will be
installed within the floodplain of each cross-section and will be monitored to evaluate
groundwater-surface water linkages. This information will be used by the R-IFS to evaluate
Project effects on existing riparian communities. These same cross-sections will be used to meet
IFS aquatic study objectives for summer and winter flow conditions by characterizing
groundwater and surface-water interactions. Groundwater and surface-water levels will be
measured at these cross-sections and within associated lateral habitats to understand relationships
between groundwater conditions and aquatic surface-water habitats.
Another Groundwater Study activity that was already planned for the Lower River Segment is
described in RSP Section 7.5.4.8 – Shallow Groundwater Users. This study objective includes
the measurement of private water wells in the overall study area and the adjacent surface water
levels on the river to help determine the potential Project effects on shallow well users.
4.2.4. Fisheries
The Fish Distribution and Abundance Study (FDAS) presented in RSP Section 9.6 discussed
sampling for relative abundance in the Lower River Segment Geomorphic Reach LR-1.
However, results of the recently completed Open Water Flow Modeling and hydrologic and
geomorphologic analysis have indicated the need to assess Project effects further downstream
within Geomorphic Reaches LR-2 to LR-4. The size of the river, and the density and complexity
of channels and channel morphologies in the Lower River Segment create difficult sampling
conditions for fish. Because one of the primary goals of the FDAS is to define species presence
and relative abundance at different locations in the river, AEA will rely upon a systematic
transect approach whereby fish sampling sites will be selected within habitat units encountered
along a transect. For this, a total of ten transects will be located within the Lower River Segment
extending from PRM 102.4 to 32.3. These transects will be spaced at 7.4-mile intervals and
selected with a random start point (Figure 20).
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FERC Project No. 14241 Page 29 March 2013
Because of the complex nature of the Lower River Segment, most transects will span multiple
habitat types (e.g., main channel, side channel, upland slough, and side slough).
Correspondingly, one habitat unit of each type encountered will be selected for sampling along
each transect (see Figure 5.4-3 in Susitna River Fish Distribution and Abundance
Implementation Plan). Where multiple habitat units of the same type occur, units will be
randomized and one selected. Fish distribution and abundance sampling will then be conducted
monthly (during open water periods) along a 40-meter length of the unit, starting at the
downstream end. If the randomly selected habitat unit is totally inaccessible to field crews, then
a second randomly selected habitat unit will be sampled.
The results of the 2013 FDAS, coupled with results of the Salmon Escapement Study (RSP
Section 9.7) will provide valuable information concerning the distribution and habitat use by
different fish species in the Lower River Segment. The need for additional sampling sites (or
modifications in sampling methodologies) in 2014 will include consideration of:
Extent to which the 2013 sites captured representative habitat types as determined based
on results of detailed habitat mapping (to be completed in 2013);
Extent to which 2013 sites aligned with FA-IFS sites and HSC sampling sites and
whether inferences can be drawn relative to fish use of specific habitat types; and
Capture efficiency of sampling methods (gear types) used in 2013 (i.e., potential need to
refine sampling techniques).
4.2.5. Geomorphology
The Geomorphology Study (RSP Section 6.5) contains several efforts that encompass the entire
Lower River Segment. These efforts include the delineation and characterization of geomorphic
reaches (RSP Section 6.5.4.1), analysis of sediment supply and transport (RSP Section 6.5.4.3),
identification of channel change based on historical aerial analysis (RSP 6.5.4.4), reconnaissance
level of assessment of potential channel change (RSP Section 6.5.4.6), comparison of 1980s and
2012 riverine macrohabitat versus flow relationships for selected Lower River sites (RSP Section
6.5.4.7) and large woody debris mapping and analysis (RSP Section 6.5.4.9). The Fluvial
Geomorphology Modeling Study (RSP Section 6.6) ended the modeling efforts about 8 miles
below Sunshine at PRM 79.
Based on the decision to evaluate effects further downstream in the Lower River, additional
efforts will be conducted under the Fluvial Geomorphology Modeling Study. Figure 20
identifies the area for extension of the 1-D model. The extension of the Fluvial Geomorphology
Modeling Study will have two primary objectives:
Determine potential Project effects on the geomorphology in the portion of the Lower
River Segment from PRM 79 downstream to PRM 29.9 (Susitna Station); and
Support the evaluation of Project effects by other studies in their resource areas providing
channel output data and assessment of potential changes in the geomorphic features that
help comprise the aquatic and riparian habitats of the Lower Susitna River Segment from
PRM 79 downstream to PRM 29.9 (Susitna Station).
The primary aspect to this effort will be the extension of the 1-D bed evolution model from PRM
79 downstream to PRM 29.9. The extension of the 1-D bed evolution model, along with the
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FERC Project No. 14241 Page 30 March 2013
open-water flow routing model, will allow a reach level determination of the sediment balance
within the Lower River Segment. It will also allow for evaluation of key physical processes such
as the extent of inundation, mobilization of bed material on bars and tractive forces associated
with the potential scouring of vegetation. The overall development, data collection, calibration
and application of the 1-D bed evolution model will be similar to that described in the RSP for
the portion of the model from PRM 187.1 (RM 184) to PRM 79 (RM 75). The effort will be
performed in conjunction with the R-IFS (RSP Section 8.6) and the Ice Processes Study (RSP
Section 7.6) to provide an integrated determination of potential channel change in the Lower
River.
Data collection efforts to support the 1-D bed evolution model development and application
include:
Survey approximately 50 cross sections between PRM 79 and PRM 29.9. These would
serve both the 1-D bed evolution model and the open-water flow routing model. The
cross sections would extend across the main channel and braid plain as well as
incorporate significant side channels.
Collect bed material samples to characterize the bed material at selected model cross
sections. Bed material samples would include surface and subsurface and will consist of
a combination of pebble counts and bulk samples dependent on the size of the material
being sampled. It is anticipated that approximately 200 bed material samples will be
collected.
Level loggers will be installed at key main channel and side channel locations to provide
water surface elevations to calibrate the open-water flow routing model and the 1-D bed
evolution model. (This effort will be performed as part of the FA-IFS.)
Expand the USGS sediment transport and discharge measurement program to include the
Susitna River at Susitna Station and Yentna River near Susitna Station to support the
sediment-transport analysis. This will help refine the sediment transport relationships
and provide information to compare current data with the 1980s data.
Perform a field assessment of the geomorphology of the Lower River Segment
downstream to PRM 29.9 while collecting the bed material samples.
The other effort that will be conducted as part of the 2013 extension of the Fluvial
Geomorphology Modeling Study into the Lower River Segment will be the analysis of potential
Project effects at five selected tributary mouths. The tributary mouths were identified as
important habitat with the potential to be affected by the Project in the 1980s study Assessment of
Access by Spawning Salmon into Tributaries of the Lower Susitna River (Ashton and Trihey
1985). Primary issues are the influence of the Project on fish access to the tributaries and the
holding area near the tributary mouths. The potential for changes in sedimentation and
hydraulics (area of backwater, depth and velocity) will be investigated at the five selected
tributary mouths: Trapper Creek, Birch Creek, Sheep Creek, Caswell Creek and the Deshka
River (Figure 20). Sedimentation at the tributary mouths will be determined by a procedure
similar to that described in RSP Section 6.6.4.1.2.6. A hydraulic model (HEC-RAS) will be
developed for the downstream end of each tributary to support the determination of changes in
hydraulic conditions and sediment transport characteristics.
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Data collection efforts to support the sediment transport and hydraulic analysis at the selected
tributary mouths include:
Survey of approximately ten cross sections on the lower portion of each of the five
selected tributaries. The number of cross sections at individual tributaries will depend on
the extent of mainstem backwater influence. Transects from the FA-IFS effort may
provide a portion of the cross sections required;
Survey a thalweg profile for each tributary from the confluence with the mainstem (or the
branch of the mainstem) upstream to the location of the upstream most cross section
above the backwater influence;
Collect bed material samples to characterize the bed material in the backwater and
confluence area with the main stem and at a location upstream of the backwater effect
that can be used to estimate bed load transport. Approximately 10 to 15 bed material
samples are will be collected per tributary;
Level loggers will be installed at the lower end of each tributary in the backwater area
and on each tributary upstream of the extent of backwater. Continuous recording of
water surface elevations will be performed (As noted above, this effort will be performed
as part of the FA-IFS); and
Flow measurements will be collected near the level loggers upstream of the backwater
area to establish rating curves on each tributary for the purpose of developing the flow
record for the tributary. (This effort will be performed as part of the FA-IFS.)
Results from the 2013 studies for the Lower Susitna River Segment, modified as described
above, will provide a basis for assessing the need to perform further data collection and analysis
in 2014.
4.2.6. Ice Processes
The Ice Processes Study includes several components that encompass the entire length of the
Lower River Segment (RSP Section 7.6.4.1). Aerial reconnaissance and global positioning
system (GPS) mapping of ice features, including ice jams, ice bridges, frazil accumulations, and
open leads during the break-up and freeze-up periods will be performed from tidewater to the
Oshetna River confluence (from PRM 0 to PRM 235). The data collected include concentrations
of frazil ice, locations of ice bridges, ice jams, overflow, and open leads, timing of ice-cover
progression, geo-referenced photographs, and videos of ice processes.
Time-lapse cameras will monitor break-up and freeze-up at locations corresponding to flow
routing model instrumentation, key ice processes, and fish habitat locations (RSP Section
7.6.4.2). Time-lapse cameras are set to take photos of the main channel or a side channel/slough
at one-hour intervals, and the results are compiled into a video. Key information to be derived
from time-lapse videos includes the timing of ice cover advance past the camera location, the
relative abundance of frazil ice visible in the channel during freeze-up, the growth of border ice
during freeze-up from the shore, and the local interaction of ice with the floodplain. During
breakup, information derived from the cameras includes documentation of increase of open
leads, overflow, ice runs and jams, and local interaction of ice with the floodplain. Immediately
post-breakup, crews conduct a foot reconnaissance of each camera location, documenting
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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FERC Project No. 14241 Page 32 March 2013
locations of stranded ice, damaged vegetation, and any erosion or scour attributed to breakup
processes.
AEA-operated stream gages coincide with four of these sites. At stream gage locations, air
temperature is recorded all winter, and water stage and water temperature are recorded until
freeze-up, after which the sensors often are lost or buried. The sites are depicted in Figure 23
and listed below.
PRM 15.1 – Alexander (camera): Near upper tidal influence and initial bridging location.
PRM 17.4 – Susitna River near Flathorn Lake (ESS10, camera and gage): Near upper
tidal influence.
PRM 24.7 – Susitna River near Dinglishna Hill (ESS15, camera and gage): Just above
upper tidal influence.
PRM 30 – Susitna River at Susitna Station (ESS20 (two cameras and gage): Confined
channel below the Yentna confluence.
PRM 64.1 – Rustic Wilderness Side Channel (camera): Wide braided section with side
channels; fish habitat study site in 1984.
PRM 91.8 – Main channel and side channel near Birch Creek (camera): Wide, braided
section and side channel. Fish habitat study site in 1984.
PRM 98.4 – Susitna River near Twister Creek (ESS30 camera and gage): Immediately
below Three Rivers confluence.
Two reaches have been selected for HEC-RAS modeling of winter flows pre-and post-Project in
order to estimate the maximum increase in winter stages. These two locations are downstream of
the Sunshine Bridge, between PRM 80 and PRM 85, and downstream of the Yentna confluence,
from PRM 28 to PRM 32. These reaches were chosen because they are relatively simple
channels compared to much of the Lower River, which makes them suited to HEC-RAS
modeling, and because transect data are available. The simple nature of the channels means that
Project-induced staging effects will be somewhat amplified, thus the analysis will be
conservative. These two reaches also represent the range of flows seen in the Lower River, and
thus will reflect the likely range of Project-induced increases in winter stage.
4.2.7. Water Quality
AEA has reviewed the water quality study plans in light of the 2012 study results and has
determined that there is no need to modify the water quality sampling effort beyond that
described in the RSP Section 5.5 through Section 5.7. The Baseline Water Quality Study and the
Water Quality Modeling Study described in RSP Sections 5.5 and 5.6, respectively, are intended
to study all three river segments of the Susitna River from the Oshetna River (PRM 235.1) to
Alexander Creek (PRM 20); Table 20 and Figure 24 show specific sampling locations by river
mile. The primary objective of the water quality studies is to support the overall evaluation of
Project effects (construction and operations) on water quality characteristics in the river. This
will be accomplished in part through development of a water quality model (RSP Section 5.6)
that can be used to predict how Project operations may influence existing water quality
conditions.
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FERC Project No. 14241 Page 33 March 2013
The work in the Lower River Segment, as described in the RSP, will consist of the following
elements:
Collection of stream temperature and meteorological data.
Characterization of surface water physical, chemical, and bacterial conditions in the
Lower Susitna River.
Measurement of baseline metals concentrations in sediment and fish tissue.
Completion of Thermal Infrared (TIR) imaging of the Lower River Segment to identify
areas of groundwater inflow and potential thermal refugia.
Documentation of historical water quality data and combining those data with data
generated from the Baseline Water Quality Study. The combined data set will be used in
the Water Quality Modeling Study to predict Project impacts under various operations.
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 34 March 2013
5. REFERENCES
AEA (Alaska Energy Authority). 2011. Pre-Application Document. Susitna-Watana
Hydroelectric Project FERC Project No. 14241. Alaska Energy Authority, Anchorage,
Alaska.
Andrews E.D. 1980. Effective and bankfull discharges of streams in the Yampa River basin,
Colorado and Wyoming. Journal of Hydrology 46: 311–330.
Andrews, E.D. 1984. Bed-material entrainment and hydraulic geometry of gravel-bed rivers in
Colorado. Bull. Geol. Soc. Am. 95: 371–378.
Ashton, W.W., and E.W. Trihey. 1985. Assessment of Access by Spawning Salmon into
Tributaries of the Lower Susitna River. R&M Associates and E.W. Trihey and
Associates, Final Report to Alaska Power Authority. 66 pp.
Bovee, K. 1982. A guide to stream habitat analysis using the instream flow incremental
methodology. U.S. Fish and Wildlife Service. FWS/OBS - 82/26.
Emmett, W.W. 1972. The Hydraulic geometry of some Alaska streams south the Yukon River.
U.S. Geological Survey Open-file Report 72-0108: 110 p.
Grant, G.E., J.C. Schmidt, and S.L. Lewis. 2003. A geological framework for interpreting
downstream effects of dams on rivers. AGU, Geology and Geomorphology of the
Deschutes River, Oregon, Water Science and Application 7.
HDR. 2013. Middle Susitna River Segment remote line habitat mapping technical memo.
Prepared for Alaska Energy Authority, Anchorage, Alaska.
Hey, R D., and C.R. Thorne. 1986. Stable channels with mobile gravel beds. J. Hydraul. Eng.
112.8: 671–689.
Julien, P.Y., and J. Wargadalam. 1995. Alluvial channel geometry: Theory and applications. J.
Hydraul. Eng. 121.4: 312–325.
Langbein, W.B. 1964. Geometry of River Channels. J. Hydraulics Div. ASCE 90, HY2, 301-
312.
Legendre, Pierre, and Louis Legendre. 2012. Numerical Ecology. Third English Edition.
Elsevier, Amsterdam, The Netherlands.
Leopold, L.B., and T. Maddock. 1953. The hydraulic geometry of stream channels and some
physiographic implications. U.S. Geological Survey Professional Paper 252; 57 p.
Montgomery, D. 1999. Process domains and the river continuum. Journal of the American
Water Resources Association 35 (2): 397-410.
Parker, G., 1979. Hydraulic geometry of active gravel rivers. Journal of the Hydraulics
Division. v. 105. no. HY9: 1185-1201.
Payne, T.R., S.D. Eggers, and D.B. Parkinson. 2004. The Number of Transects Required to
Compute a Robust PHABSIM Habitat Index. Hydroecol Appl. 14(1): 458-465.
R&M Consultants, Inc. and Trihey & Associates. 1985a. Response of aquatic habitat surface
areas to mainstem discharge in the Yentna to Talkeetna reach of the Susitna River.
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 35 March 2013
Prepared under contract to Harza-Ebasco, for Alaska Power Authority, document No.
2774, June.
R2 Resource Consultants. 2013a. Draft Susitna River Fish Distribution and Abundance
Implementation Plan. Prepared for Alaska Energy Authority. January 2013.
R2 Resource Consultants, 2013b. Draft Technical Memorandum, Selection of Focus Areas and
study sites in the Middle Susitna River for instream flow and joint resource studies –
2013 and 2014. Prepared for Alaska Energy Authority. January 31, 2013.
R2 Resource Consultants, GW Scientific, Brailey Hydrologic, and Geovera. 2013. Open-water
HEC-RAS flow routing model. Prepared for Alaska Energy Authority. January 2013.
Tetra Tech, Inc. 2013. 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 (FERC No. 14241), prepared for Alaska Energy Authority,
Anchorage, Alaska.
Tetra Tech, Inc. 2013a. Stream Flow Assessment. Susitna-Watana Hydroelectric Project. 2012
Study Technical Memorandum. Prepared for the Alaska Energy Authority. Anchorage,
Alaska.
Tetra Tech, Inc. 2013b. 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.
Tetra Tech, Inc. 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, Inc. 2013d. Initial geomorphic reach delineation and characterization, Middle and
Lower Susitna River segments, 2012 Study Technical Memorandum. Prepared for the
Alaska Energy Authority. Anchorage, Alaska. U.S. Geological Survey. 2012.
Hydraulic Modeling in the Physical Habitat Simulation System (PHABSIM).
http://www.fort.usgs.gov/Publications/
Williams G.P. 1978. Bankfull discharge of rivers. Water Resources Research 14: 1141–1154.
Williams, J.G. 1996. Lost in space: minimum confidence intervals for idealized PHABSIM
studies. Transactions of the American Fisheries Society. 125: 458-465.
Wolman, M.G., and J.P. Miller. 1960. Magnitude and frequency of forces in geomorphic
processes. Journal of Geology 68: 54–74.
Wolman, M.G., and R. Gerson. 1978. Relative scales of time and effectiveness of climate in
watershed geomorphology. Earth Surface Processes 3: 189-208.
.
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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FERC Project No. 14241 Page 36 March 2013
6. TABLES
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FERC Project No. 14241 Page 37 March 2013
Table 1. Locations, descriptions and selection rationale of final Focus Areas for detailed study in the Middle River Segment of the Susitna River. Focus Area identification numbers (e.g., Focus Area 184) represent the truncated Project River Mile (PRM) at the downstream end of
each Focus Area.
Focus
Area ID
Common
Name Description
Geomorphic
Reach
Location (PRM)
Area Length (mi)
Habitat Types Present
Fish use in
1980s
Instream Flow
Studies in 1980s
Rationale for Selection Main Channel, Single Main Channel, Split Side Channel Tributary Mouth Side Slough Upland Slough Beaver Complex Upstream Downstream Spawning Rearing IFG DIHAB RJHAB Focus
Area-
184
Watana Dam
Area approximately 1.4
miles downstream of dam
site
MR-1 185.7 184.7 1.0 X X X N/A N/A N/A N/A N/A Focus Area-184 length comprises 50% of MR-1 reach length (2 miles long) and contains split
main channel and side channel habitat present in this reach.
Focus
Area-
173
Stephan Lake,
Complex
Channel
Wide channel near
Stephan Lake with
complex of side channels
MR-2 175.4 173.6 1.8 X X X X N/A N/A N/A N/A N/A
Focus Area-173 contains a complex of main channel and off-channel habitats within wide
floodplain. Represents greatest channel complexity within MR-2. Reach MR-2 is 15.5 miles long
and channel is generally straight with few side channels and moderate floodplain width (2-3 main
channel widths).
Focus
Area-
171
Stephan Lake,
Simple Channel
Area with single side
channel and vegetated
island near Stephan Lake
MR-2 173.0 171.6 1.4 X X X N/A N/A N/A N/A N/A
The single main channel with wide bars, single side channel and moderate floodplain channel
width in Focus Area-171 are characteristic of MR-2. Reach MR-2 channel morphology is
generally straight with few side channels and moderate floodplain width (2-3 main channel
widths).
Focus
Area-
151
Portage Creek Single channel area at
Portage Creek confluence MR-5 152.3 151.8 0.5 X X X X
Focus Area-151 is a single main channel and thus representative of the confined Reach MR-5.
Portage Creek is a primary tributary of the Middle Segment and the confluence supports high fish
use.
Focus
Area-
144
Side Channel
21
Side channel and side
slough complex
approximately 2.3 miles
upstream Indian River
MR-6 145.7 144.4 1.3 X X X X X X X X X
Focus Area-144 contains a wide range of main channel and off-channel habitats, which are
common features of Reach MR-6. Side Channel 21 is a primary salmon spawning area. Reach
MR-6 is 26 miles long (30% of Middle Segment length) and is characterized by a wide floodplain
and complex channel morphology with frequent channel splits and side channels.
Focus
Area-
141
Indian River
Area covering Indian River
and upstream channel
complex
MR-6 143.4 141.8 1.6 X X X X X X X X X
Focus Area-141 includes the Indian River confluence, which is a primary Middle Susitna River
tributary, and a range of main channel and off-channel habitats. Channel and habitat types
present in Focus Area-141 are typical of complex Reach MR-6. High fish use of the Indian River
mouth has been documented and DIHAB modeling was performed in main channel areas.
Focus
Area-
138
Gold Creek
Channel complex including
Side Channel 11 and
Slough 11
MR-6 140.0 138.7 1.3 X X X X X X X X X
The Focus Area-138 primary feature is a complex of side channel, side slough and upland slough
habitats, each of which support high adult and juvenile fish use. Complex channel structure of
Focus Area-138 is characteristic of Reach MR-6. IFG modeling was performed in side channel
habitats.
Focus
Area-
128
Skull Creek
Complex
Channel complex including
Slough 8A and Skull Creek
side channel
MR-6 129.7 128.1 1.6 X X X X X X X X X
Focus Area-128 consists of side channel, side slough and tributary confluence habitat features
that are characteristic of the braided MR-6 reach. Side channel and side slough habitats support
high juvenile and adult fish use and habitat modeling was completed in side channel and side
slough habitats.
Focus
Area-
115
Lane Creek
Area 0.6 miles downstream
of Lane Creek, including
Upland Slough 6A
MR-7 116.5 115.3 1.2 X X X X X X X X
Focus Area-115 contains side channel and upland slough habitats that are representative of MR-
7. Reach MR-7 is a narrow reach with few braided channel habitats. Upland Slough 6A is a
primary habitat for juvenile fish and habitat modeling was done in side channel and upland slough
areas.
Focus
Area-
104
Whiskers
Slough Whiskers Slough Complex MR-8 106.0 104.8 1.2 X X X X X X X X X X X Focus Area-104 contains diverse range of habitat, which is characteristic of the braided,
unconfined Reach MR-8. Focus Area-104 habitats support juvenile and adult fish use and a
range of habitat modeling methods were used in side channel and side slough areas.
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Table 2. Main channel habitat classifications by geomorphic reach in the Middle Susitna River.
Main Channel
Type
MR-1 MR-2 MR-3 MR-4 MR-5 MR-6 MR-7 MR-8
% Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft)
Main Channel 71% 12,737 74% 74,938 74% 16,470 99% 64,096 85% 26,400 28% 96,199 28% 41,538 24% 18,235
Split Main
Channel 0% - 8% 8,148 16% 3,600 0% - 15% 4,835 18% 62,885 52% 77,346 6% 4,514
Braided Main
Channel 0% - 0% - 0% - 0% - 0% - 8% 26,400 0% - 32% 24,430
Side Channel 29% 5,235 18% 17,646 9% 2,090 1% 699 0% - 46% 161,115 19% 28,723 38% 28,398
Grand Total 100% 17,972 100% 100,732 100% 22,161 100% 64,794 100% 31,235 100% 346,599 100% 147,607 100% 75,577
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Table 3. Main Channel mesohabitat classifications in the Middle Susitna River.
Main Channel Mesohabitat
MR-1 MR-2 MR-3 MR-4 MR-5 MR-6 MR-7 MR-8
% Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft)
Main Channel 71% 12,737 74% 74,938 74% 16,470 99% 64,096 85% 26,400 28% 96,199 28% 41,538 24% 18,235
Glide or Run 71% 12,737 71% 71,986 72% 16,030 28% 18,397 85% 26,400 26% 90,714 23% 33,840 24% 18,235
Pool 0% - 0% - 0% - 1% 500 0% - 0% - 0% - 0% -
Rapid 0% - 0% - 0% - 39% 25,519 0% - 0% - 0% - 0% -
Riffle 0% - 3% 2,953 2% 440 30% 19,680 0% - 2% 5,485 5% 7,698 0% -
Split Main
Channel 0% - 8% 8,148 16% 3,600 0% - 15% 4,835 18% 62,885 52% 77,346 6% 4,514
Glide or Run 0% - 8% 8,148 16% 3,600 0% - 15% 4,835 18% 61,922 42% 62,562 6% 4,514
Riffle 0% - 0% - 0% - 0% - 0% - 0% 963 10% 14,784 0% -
Braided Main
Channel 0% - 0% - 0% - 0% - 0% - 8% 26,400 0% - 32% 24,430
Glide or Run 0% - 0% - 0% - 0% - 0% - 7% 24,922 0% - 32% 24,008
Riffle 0% - 0% - 0% - 0% - 0% - 0% 882 0% - 1% 422
Unidentified 0% - 0% - 0% - 0% - 0% - 0% 595 0% - 0% -
Side Channel 29% 5,235 18% 17,646 9% 2,090 1% 699 0% - 46% 161,115 19% 28,723 38% 28,398
Glide or Run 29% 5,235 6% 5,716 8% 1,677 0% - 0% - 26% 89,118 13% 19,080 28% 21,528
Pool 0% - 0% - 0% - 1% 342 0% - 0% - 0% - 0% -
Riffle 0% - 0% - 0% - 1% 357 0% - 1% 2,522 0% 279 9% 6,870
Unidentified 0% - 12% 11,930 2% 414 0% - 0% - 20% 69,475 6% 9,363 0% -
Grand Total 100% 17,972 100% 100,732 100% 22,161 100% 64,794 100% 31,235 100% 346,599 100% 147,607 100% 75,577
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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FERC Project No. 14241 Page 40 March 2013
Table 4. Off channel habitats classified in the Middle Susitna River.
Off-Channel
Habitats
MR-1 MR-2 MR-3 MR-4 MR-5 MR-6 MR-7 MR-8
% Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft) % Total (ft)
Backwater n/a - 0.6% 201 0.0% - 100.0% 91 0.0% - 1.5% 1,236 2.4% 1,458 2.0% 453
Side Slough n/a - 51% 16,130 100% 712 0% - 100% 4,482 47% 38,898 16% 10,038 27% 6,195
Beaver Complex n/a - 0% - 0% - 0% - 0% - 7% 5,393 4% 2,584 0% -
Side Slough n/a - 51% 16,130 100% 712 0% - 100% 4,482 41% 33,505 12% 7,454 27% 6,195
Upland Slough n/a - 48% 15,261 0% - 0% - 0% - 51% 42,361 81% 50,067 71% 16,190
Beaver Complex n/a - 0% - 0% - 0% - 0% - 15% 12,512 12% 7,171 0% -
Upland Slough n/a - 48% 15,261 0% - 0% - 0% - 36% 29,849 68% 42,027 71% 16,190
Grand Total n/a - 100% 31,592 100% 712 100% 91 100% 4,482 100% 82,495 100% 61,563 100% 22,838
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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Table 5. Tributary features classified in the Middle Susitna River. Potential fish-bearing tributaries were identified as a
subset of those classified by the habitat mapping.
Tributary Feature MR-1 MR-2 MR-3 MR-4 MR-5 MR-6 MR-7 MR-8
Tributary 0 39 6 10 3 63 21 4
Tributary Mouth 0 10 3 8 2 11 3 0
Clear Water Plume 0 5 2 0 1 4 1 0
Potential Fish-bearing
Tributaries 0 12 3 5 1 22 13 1
Table 6. Metrics used to compare the representation and proportionality of habitat types between focus areas and non-
focus areas within each geomorphic reach.
Level Habitat Type Comparison Metric Numerator Denominator
Macro-
Habitat
Main Channel Percent of main channel that
is single unsplit main channel
Length of main channel
habitat (HDR)
Total length of main
channel (thalweg, R2)
Split Main Channel Percent of main channel that
is in split main channel
Length of main channel
that is in split main
channel (R2 calculated)
Total length of main
channel (thalweg, R2)
Braided Main Channel Percent of main channel that
is in braided main channel
Length of main channel
that is in braided main
channel (R2 calculated)
Total length of main
channel (thalweg, R2)
Side Channel Side channel length per river
mile
Total length of side
channels (HDR)
Total length of main
channel (thalweg, R2)
Upland Slough Upland slough length per
river mile
Total length of upland
slough habitat (HDR)
Total length of main
channel (thalweg, R2)
Side Slough Side slough length per river
mile
Total length of side
channel habitat (HDR)
Total length of main
channel (thalweg, R2)
Backwater density of backwaters
(#/mile) # backwaters (HDR) Total length of main
channel (thalweg, R2)
Tributary density of tributaries (#/mile) # tributaries (HDR) Total length of main
channel (thalweg, R2)
Tributary Mouth density of tributary mouths
(#/mile)
# Tributary Mouths
(HDR)
Total length of main
channel (thalweg, R2)
Clear Water Plume density of plumes (#/mile) # plumes (HDR) Total length of main
channel (thalweg, R2)
Mesohabitat
Glide or Run Percent of main/side channel
habitat in glide/run
Total length of Glide or
Run (HDR)
Total Length of Main +
Side Channel Habitat
(HDR)
Riffle Percent of main/side channel
habitat in riffle
Total length of Riffle
(HDR)
Total Length of Main +
Side Channel Habitat
(HDR)
Beaver Complex Percent of slough habitat that
is beaver complex
Total length of Beaver
Complex Habitat (HDR)
Total length of slough
habitat (HDR)
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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FERC Project No. 14241 Page 42 March 2013
Table 7. Estimated bias for each proportionality metric (total for reach – focus area) where estimates could be made.
Statistical comparison was made using a t-test or nonparametric alternative when the sample size (number of geomorphic
reaches with bias estimate) was greater than three.
MR-1 MR-2 MR-5 MR-6 MR-7 MR-8 Average Bias p-value
Main Channel -5% -8.7% -18% 40% -33% -5% 0.70
Split Main 5% 8.7% 22.4% -40% 7% 0.6% 0.63
Braided Main -4.0% 26% 11% n/a
Side Channel -0.33 -0.10 0.021 0.13 -1.02 -0.26 0.28
Side Slough -0.46 0.155 -0.14 0.13 -0.42 -0.15 0.32
Upland Slough 0.04 -0.02 -0.43 -0.29 -0.1740 0.22
Backwaters 0.07 -0.018 -1.35 0.19 -0.28 1.00
Tributaries 0.18 -1.64 0.337 0.10 -0.66 -0.34 0.41
Tributary Mouth 0.36 -1.46 0.081 0.20 -0.20 0.88
Clear Water Plumes 0.33 -1.64 -0.018 0.07 -0.31 1.00
Beaver Complex -9.8% -25% -18% n/a
Glides/Runs -3.3% 4.43% 14.0% 4.0% 4.8% 0.27
Riffles 3.3% -4.43% -14.0% -4.0% -4.8% 0.27
Table 8. Identification of existing focus area boundaries and counterpart locations of areas selected via a random
systematic approach.
Geomorphic
Reach
Geomorphic Reach Current Focus Area Random Focus Area
Start End Length Start End Length Start End Length
MR-1 187.1 184.6 2.5 185.7 184.7 1 186.2 185.2 1
MR-2 184.6 169.6 15 175.4 173.6 1.8 181.4 179.8 1.6
173 171.6 1.4 175.0 173.4 1.6
MR-5 153.9 148.4 5.5 152.3 151.8 0.5 152.8 152.3 0.5
MR-6 148.4 122.7 25.7
145.7 144.4 1.3 146.8 145.3 1.5
143.4 141.8 1.6 140.8 139.3 1.5
140 138.7 1.3 134.8 133.3 1.5
129.7 128.1 1.6 128.8 127.3 1.5
MR-7 122.7 107.8 14.9 116.5 115.3 1.2 117.8 116.6 1.2
MR-8 107.8 102.4 5.4 106 104.8 1.2 104.9 103.7 1.2
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Table 9. Comparison of simulated random focus areas to project focus areas by geomorphic reach for main channel habitat (FA=project focus areas; RFA=random
systematic focus areas, Total=Total for the geomorphic reach.)
MR-1 MR-2 MR-5 MR-6 MR-7 MR-8
FA RFA Total FA RFA Total FA RFA Total FA RFA Total FA RFA Total FA RFA Total
%Main Channel in
Single Main Channel
100
%
100
%
100
%
100
% 78% 95% 100
%
100
% 91% 88% 85% 71% 36% 57% 53% 6% 51% 66%
% Main Channel in
Split Main Channel 0% 0% 0% 0% 22% 5% 0% 0% 9% 0% 15% 22% 64% 43% 47% 39% 5% 8%
% Main Channel in
Braided Main Channel 0% 0% 0% 0% 0% 0% 0% 0% 0% 12% 0% 6% 0% 0% 0% 55% 44% 26%
Side Channel
Length/Main Channel
Length
0.51 0.80 0.49 0.26 0.43 0.22 0.00 0.00 0.07 1.02 1.17 1.19 0.23 0.52 0.37 1.15 1.42 1.02
Side Slough
Length/Main Channel
Length
0.00 0.00 0.00 0.54 0.03 0.20 0.00 0.00 0.17 0.36 0.50 0.29 0.00 0.00 0.13 0.36 0.00 0.22
Upland Slough
Length/Main Channel
Length
0.00 0.00 0.00 0.16 0.37 0.19 0.00 0.00 0.00 0.28 0.15 0.31 1.18 0.51 0.63 0.60 0.00 0.58
Backwaters per River
Mile 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.1 0.2 0.2 1.5 0.0 0.2 0.0 0.0 0.2
Tributaries per River
Mile 0.0 0.0 0.0 0.7 1.3 2.4 0.5 0.0 0.2 0.9 4.2 2.2 0.8 2.6 1.5 1.4 0.0 0.6
Tributary Mouths per
River Mile 0.0 0.0 0.0 0.2 0.6 0.7 0.5 0.0 0.2 0.3 0.7 0.4 0.0 1.7 0.3 0.0 0.0 0.0
Clear Water Plumes
per River Mile 0.0 0.0 0.0 0.0 0.0 0.3 0.5 0.0 0.2 0.1 0.2 0.2 0.0 0.9 0.1 0.0 0.0 0.0
Proportion of Slough
Habitat in Beaver
Complex
n/a n/a n/a n/a n/a n/a n/a n/a n/a 32% 14% 22% 0% 81% 13% n/a n/a n/a
Proportion of Main
Channel in Glide/Run
100
%
100
%
100
%
100
%
100
% 97% 100
%
100
% 98% 93% 97% 96% 70% 92% 84% 90% 92% 90%
Proportion of Main
Channel in Riffle 0% 0% 0% 0% 0% 3% 0% 0% 2% 7% 3% 4% 30% 8% 16% 10% 8% 10%
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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FERC Project No. 14241 Page 44 March 2013
Table 10. Estimated bias for each proportionality metric (total for reach – focus area) where estimates could be made for
random focus areas. Statistical comparison was made using a t-test or nonparametric alternative when the sample size
(number of geomorphic reaches with bias estimate) was greater than three.
MR-1 MR-2 MR-5 MR-6 MR-7 MR-8
Average
Bias p-value
Main Channel 17% -9.5% -14% 17% 60% 14% 0.34
Split Main -17% 9.5% 7.5% -17% -31% -9.6% 0.29
Braided Main 6.3% -28% -11% n/a
Side Channel -0.31 -0.20 0.073 0.018 -0.15 -0.41 -0.16 0.084
Side Slough 0.17 -0.19 0.63 0.58 0.30 0.22
Upland Slough -0.17 0.17 0.13 -0.39 0.22 -0.0058 0.96
Backwaters 0.07 -0.011 0.20 0.19 0.11 0.12
Tributaries 1.2 0.20 -2.0 -1.1 0.57 -0.22 0.71
Tributary Mouth 0.045 0.40 -0.28 -1.4 -0.32 0.48
Clear Water Plumes 0.33 0.20 -0.011 -0.78 -0.07 0.81
Beaver Complex 7.9% -68% -30% n/a
Glides/Runs -3.3% -2.0% -0.54% -8.4% -1.9% -3.2% 0.078
Riffles 3.3% 2.0% 0.54% 8.4% 1.9% 3.2% 0.078
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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Table 11. Riparian process domain #1 (RPD1). Plant communities typed, and measured, along transects using Alaska
Vegetation Classification (AVC) Level III (1992) community descriptions. First column describes communities identified
along transects in RPD1 and remaining columns describe communities within Focus Areas in the riparian process
domain. The sum of lengths (line-intercept sampling method; length in meters) for each cover type are reported in
parentheses.
Plant Community
RPD1 (PRM
168.25-187)
FA-184
Watana Dam
FA-173 Stephan
Lake Complex
FA-171
Stephan Lake
Simple
Closed Conifer Forest Yes
(3625.5) No Yes
(44.4)
Yes
(134)
Open Conifer Forest Yes
(7080.3)
Yes
(69.9)
Yes
(407.9)
Yes
(111)
Conifer Woodland Yes
(849.7)
Yes
(105.4) No No
Closed Mixed Forest Yes
(2912)
Yes
(81.1)
Yes
(268.3)
Yes
(314.1)
Open Mixed Forest Yes
(5567.7)
Yes
(134.7)
Yes
(746)
Yes
(715.4)
Mixed Woodland Yes
(250.8) No Yes
(77.7)
Yes
(35.9)
Closed Broadleaf Forest Yes
(250.7)
Yes
(8.5)
Yes
(81.5) No
Open Broadleaf Forest Yes
(329.4) No Yes
(156.8)
Yes
(13.1)
Broadleaf Woodland Yes
(31.3) No No No
Closed Alder/Willow Shrub Yes
(750.9)
Yes
(28.4)
Yes
(246.9)
Yes
(24.8)
Open Alder/Willow Shrub Yes
(585.6)
Yes
(35)
Yes
(155.5)
Yes
(47)
Herbaceous Yes
(470.8) No Yes
(47.4) No
Partially Vegetated Yes
(228.4)
Yes
(27.7)
Yes
(119.7)
Yes
(25.4)
Non-vegetation cover types1 Yes
(16012.4)
Yes
(810.8)
Yes
(1857.3)
Yes
(1164.2)
Total Transect Length 38945.4 1301.6 4209.4 2585.0
# of Plant Communities 13 8 11 9
% Plant Communities overlap with RPD1 100% 62% 85% 69%
Notes:
1 Includes channel types (main channel, side channel, side slough, upland slough, etc.) as well as roads, and other
human disturbances.
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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FERC Project No. 14241 Page 46 March 2013
Table 12. Riparian process domain #3 (RPD3). Plant communities typed, and measured, along transects using Alaska
Vegetation Classification (AVC) Level III (1992) community descriptions. First column describes communities identified
along transects in RPD3 and remaining columns describe communities within Focus Areas in the riparian process
domain. The sum of lengths (line-intercept sampling method; length in meters) for each cover type are reported in
parentheses.
Plant Community
RPD3
(PRM 108-153.5)
FA-151
Portage Creek
FA-144
Side
Channel 21
FA-141
Indian River
FA-138
Gold Creek
FA-128
Skull
Creek Complex
FA-115
Lane Creek
Closed Conifer Forest No No No No No No No
Open Conifer Forest Yes
(1243.9) No No No No No No
Conifer Woodland Yes
(307.6) No No No No No No
Closed Mixed Forest Yes
(5325.2) No Yes
(20.8) No No No No
Open Mixed Forest Yes
(15444.3)
Yes
(40.1)
Yes
(30.4)
Yes
(490.5)
Yes
(257.6)
Yes
(7.6)
Yes
(322.6)
Mixed Woodland Yes
(6053.8) No Yes
(125.5)
Yes
(215.4)
Yes
(73.7)
Yes
(816.8)
Yes
(233)
Closed Broadleaf Forest Yes
(10657.8) No Yes
(645.7)
Yes
(328)
Yes
(1230)
Yes
(307.9)
Yes
(263)
Open Broadleaf Forest Yes
(17955.5)
Yes
(9.5)
Yes
(403.1)
Yes
(140)
Yes
(1271.9)
Yes
(2240.5)
Yes
(674.6)
Broadleaf Woodland Yes
(3480.4)
Yes
(31.2) No No No Yes
(61.9)
Yes
(197.1)
Closed Alder/Willow Shrub Yes
(6008.8)
Yes
(24)
Yes
(232.9)
Yes
(34.9)
Yes
(439.5)
Yes
(268.8)
Yes
(21.5)
Open Alder/Willow Shrub Yes
(6188.6) No Yes
(327.1)
Yes
(330.9)
Yes
(223.3)
Yes
(307.1)
Yes
(61.2)
Herbaceous Yes
(4138.2) No No No Yes
(234.9)
Yes
(21.3)
Yes
(183.5)
Partially Vegetated Yes
(677) No Yes
(10.6)
Yes
(48.9)
Yes
(50.9) No No
Non-vegetation cover types1 Yes
(65375.2)
Yes
(456)
Yes
(2808.3)
Yes
(2360.6)
Yes
(1944.8)
Yes
(3313.2)
Yes
(2553.4)
Total Transect Length 142856 561 4604 3949 5727 7345 4510
# of Plant Communities 12 4 9 7 8 8 8
% Plant Communities overlap
with RPD3 100% 33% 75% 58% 67% 67% 67%
Notes:
1 Includes channel types (main channel, side channel, side slough, upland slough, etc.) as well as roads, and other
human disturbances.
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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FERC Project No. 14241 Page 47 March 2013
Table 13. Riparian process domain #4 (RPD4). Plant communities typed, and measured, along transects using Alaska
Vegetation Classification (AVC) Level III (1992) community descriptions. First column describes communities identified
along transects in RPD4 and remaining columns describe communities within Focus Areas in the riparian process
domain. The sum of lengths (line-intercept sampling method; length in meters) for each cover type are reported in
parentheses.
Plant Community
RPD4
(PRM
104-107.75) Whiskers Slough
Closed Conifer Forest No No
Open Conifer Forest Yes
(557.3)
Yes
(71.5)
Conifer Woodland Yes
(87) No
Closed Mixed Forest Yes
(5285.1)
Yes
(109.6)
Open Mixed Forest Yes
(20752.7)
Yes
(10185.8)
Mixed Woodland Yes
(2727.7)
Yes
(820)
Closed Broadleaf Forest Yes
(2776.5)
Yes
(994.1)
Open Broadleaf Forest Yes
(1328.1)
Yes
(831.1)
Broadleaf Woodland Yes
(607.7)
Yes
(180.5)
Closed Alder/Willow Shrub Yes
(320.5)
Yes
(313.6)
Open Alder/Willow Shrub Yes
(508.9)
Yes
(185.3)
Herbaceous Yes
(2198.3)
Yes
(770.3)
Partially Vegetated Yes
(290.3)
Yes
(100)
Non-vegetation cover types1 Yes
(7020.7)
Yes
(2848.1)
Total Transect Length 44461 17410
# of Plant Communities 12 11
% Plant Communities overlap with RPD4 100% 92%
Notes:
1 Includes channel types (main channel, side channel, side slough, upland slough, etc.) as well as roads, and other
human disturbances.
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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Table 14. Rationale for Riparian IFS Focus Area selection
Focus Area ID Common Name Riparian IFS Riparian IFS Selection Rationale
Focus Area-184 Watana Dam
Not-selected. Floodplain vegetation occurs on only a few
mid-channel island bars. Non-focus area vegetation
sampling will be conducted in these areas.
Focus Area-173 Stephan Lake,
Complex Channel X
Focus Area captures the diversity of floodplain vegetation
types in the upper moderately confined riparian process
domain from the dam site to Devils Canyon.
Focus Area-171 Stephan Lake,
Simple Channel
Not-selected. Approximately 0.5 miles south of FA-173.
Similar vegetation types but less floodplain terrain
complexity.
Focus Area-151 Portage Creek Not-selected. Steep valley walls immediately adjacent to
channel. Floodplain vegetation is minimal.
Focus Area-144 Side Channel 21
Not-selected. Process domain representative vegetation,
however, lacking in off-channel water body and wetland
complexity.
Focus Area-141 Indian River Not selected. Very limited floodplain area.
Focus Area-138 Gold Creek X Representative floodplain vegetation types and river right
beaver dam wetland complex.
Focus Area-128 Skull Creek
Complex X Representative floodplain vegetation types and complex
off-channel water bodies and associated wetlands.
Focus Area-115 Lane Creek X
Representative floodplain vegetation types and off-
channel water bodies associated with beaver dam
wetland complex.
Focus Area-104 Whiskers Slough X
Transition riparian process domain between, Three
Rivers confluence and moderately confined riparian
process domain. Representative floodplain vegetation
types and off-channel water bodies and associated
beaver dam wetland complexes.
Table 15. List of Focus Areas selected for Riparian-IFS studies within each Riparian Process Domain.
Middle
River
Riparian Process
Domain
Location (PRM) Associated Riparian-IFS Focus Areas Upstream Downstream Focus Area ID Common Name
Location (PRM) Upstream Downstream RPD1 187 168.25 Focus Area-173 Stephan Lake, Complex Channel 175.4 173.6
RPD2 168 153.75 None N/A N/A N/A
RPD3 153.5 108
Focus Area-138 Gold Creek 140 138.7
Focus Area-128 Skull Creek Complex 129.7 128.1
Focus Area-115 Lane Creek 116.5 115.3
RPD4 107.75 104 Focus Area-104 Whiskers Slough Complex 106 104.8
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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FERC Project No. 14241 Page 49 March 2013
Table 16. Partial list of river cross-sections, and flow and water surface elevations measured in 2012 on the Susitna River
between River Miles 75 and 184. The list does not include additional measurements in late September/October. Those
measurements had not been processed at the time this study plan was prepared.
Project
River Mile
High Q Trip Mid Q Trip Low Q Trip
Date Time Discharge Date Time Discharge Date Time Discharge
PRM 225.0 6/14/12 17:57 26,932 8/9/12 15:03 11,260 -- -- --
PRM 187.2 6/17/12 16:30 27,698 8/6/12 16:13 14,707 9/15/12 13:17 7,838
PRM 186.2 6/18/12 14:13 24,493 8/6/12 17:05 14,419 9/15/12 14:05 7,630
PRM 185.5 6/18/12 16:10 25,389 -- -- -- -- -- --
PRM 185.2 6/19/12 13:00 26,676 -- -- -- -- -- --
PRM 184.9 6/19/12 15:49 27,619 8/6/12 18:24 14,239 9/15/12 14:57 7,714
PRM 184.4 6/19/12 16:51 27,886 8/7/12 12:38 14,775 9/15/12 15:52 8,353
PRM 183.3 6/20/12 13:19 29,426 8/7/12 13:35 14,183 9/15/12 16:41 8,310
PRM 182.9 6/20/12 16:01 29,218 -- -- -- -- -- --
PRM 181.6 6/20/12 17:56 29,645 8/7/12 14:44 14,705 9/15/12 17:55 8,689
PRM 179.5 6/21/12 12:28 30,866 8/7/12 15:41 14,345 9/14/12 17:05 8,361
PRM 178.5 6/16/12 18:35 29,756 8/7/12 16:37 14,799 9/14/12 17:47 8,738
PRM 176.5 6/21/12 14:40 31,240 8/8/12 12:07 14,559 9/16/12 14:50 10,768
PRM 174.9 6/21/12 16:12 31,163 -- -- -- -- -- --
PRM 173.1 6/21/12 17:39 30,571 -- -- -- 9/16/12 16:29 11,082
PRM 170.1 6/22/12 12:56 31,121 8/8/12 15:16 14,568 9/16/12 17:33 11,137
PRM 168.1 6/22/12 14:33 32,265 8/8/12 16:03 14,655 9/17/12 15:19 14,619
PRM 153.7 6/25/12 17:15 32,162 8/10/12 15:03 14,588 -- -- --
PRM 152.9 6/26/12 13:43 30,487 -- -- -- -- -- --
PRM 152.1 6/26/12 15:38 30,036 8/10/12 16:07 15,351 9/29/12 15:20 18,488
PRM 151.1 6/25/12 14:00 33,180 -- -- -- -- -- --
PRM 148.3 6/26/12 18:24 32,114 8/10/12 18:03 14,941 -- -- --
PRM 146.6 6/27/12 12:24 31,030 -- -- -- -- -- --
PRM 145.7 6/27/12 13:51 31,396 8/12/12 13:12 17,354 9/29/12 16:51 18,131
PRM 145.5 6/27/12 14:40 31,868 -- -- -- -- -- --
PRM 144.9 6/27/12 17:01 31,949 -- -- -- -- -- --
PRM 144.3 6/27/12 18:50 31,121 -- -- -- -- -- --
PRM 143.5 6/28/12 12:17 30,330 8/12/12 14:58 17,006 -- -- --
PRM 143.0 6/28/12 13:53 29,492 -- -- -- -- -- --
PRM 142.2 6/28/12 15:15 29,753 8/12/12 16:29 16,798 9/29/12 17:45 18,301
PRM 141.9 6/28/12 16:27 30,583 8/12/12 17:13 16,803 -- -- --
PRM 141.7 6/28/12 17:41 30,555 -- -- -- -- -- --
PRM 140.0 6/29/12 14:48 30,378 8/13/12 12:54 16,350 9/30/12 13:56 17,619
PRM 139.8 6/29/12 16:21 30,378 -- -- -- -- -- --
PRM 139.0 6/30/12 13:56 28,039 8/13/12 13:58 16,449 -- -- --
2013 FOCUS AREA AND STUDY SITE SELECTION – TECHNICAL MEMORANDUM
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Project River Mile
High Q Trip Mid Q Trip Low Q Trip
Date Time Discharge Date Time Discharge Date Time Discharge
PRM 138.7 6/30/12 14:51 28,230 8/13/12 14:48 16,344 -- -- --
PRM 138.1 6/30/12 16:33 28,203 -- -- -- -- -- --
PRM 137.6 6/30/12 18:13 27,893 8/13/12 16:14 16,409 9/30/12 15:00 17,382
PRM 136.7 7/1/12 13:35 26,756 -- -- -- -- -- --
PRM 136.2 7/1/12 16:06 26,943 -- -- -- -- -- --
PRM 135.0 7/1/12 18:33 26,526 8/13/12 17:41 15,627 -- -- --
PRM 134.3 7/2/12 12:16 25,463 -- -- -- 10/1/12 13:40 15,568
PRM 134.1 7/2/12 13:18 26,166 8/14/12 13:14 16,491 -- -- --
PRM 133.8 7/2/12 14:30 25,715 8/14/12 14:05 16,275 -- -- --
PRM 133.3 7/2/12 16:22 25,678 -- -- -- -- -- --
PRM 132.6 7/2/12 17:57 25,046 8/14/12 15:17 16,039 -- -- --
PRM 131.4 7/3/12 22:08 28,628 -- -- -- -- -- --
PRM 129.7 7/3/12 17:33 28,243 8/14/12 17:00 16,330 10/1/12 16:16 15,731
PRM 128.1 7/4/12 15:40 26,748 8/15/12 12:50 15,926 -- -- --
PRM 126.8 7/4/12 17:22 27,608 8/15/12 13:40 16,078 10/1/12 17:02 15,582
PRM 126.1 7/5/12 14:24 27,248 -- -- -- -- -- --
PRM 125.4 7/5/12 16:38 26,427 -- -- -- -- -- --
PRM 124.1 7/5/12 18:11 26,132 8/15/12 14:27 16,161 10/1/12 17:42 15,582
PRM 123.7 7/6/12 12:18 23,875 -- -- -- -- -- --
PRM 122.7 7/6/12 14:23 23,331 -- -- -- -- -- --
PRM 122.6 7/6/12 15:59 22,890 8/15/12 16:13 16,287 -- -- --
PRM 120.7 7/6/12 17:19 22,687 -- -- -- -- -- --
PRM 119.9 7/7/12 12:19 20,715 8/16/12 12:54 16,005 10/3/12 14:47 13,998
PRM 118.4 7/7/12 14:06 20,656 -- -- -- -- -- --
PRM 117.4 7/7/12 16:15 20,747 -- -- -- -- -- --
PRM 116.6 7/7/12 17:36 20,665 8/16/12 14:15 16,136 10/3/12 15:53 14,323
PRM 116.3 7/8/12 12:42 23,766 -- -- -- -- -- --
PRM 115.7 7/8/12 14:05 25,006 -- -- -- -- -- --
PRM 115.4 7/8/12 16:13 25,958 -- -- -- -- -- --
PRM 114.4 7/8/12 18:29 25,860 -- -- -- -- -- --
PRM 113.6 7/9/12 14:23 28,329 8/16/12 16:38 16,311 10/3/12 16:41 13,476
PRM 111.9 7/9/12 15:23 28,296 -- -- -- -- -- --
PRM 110.5 7/9/12 16:46 28,825 8/17/12 14:57 15,254 10/3/12 17:33 14,172
PRM 108.3 -- -- -- 8/17/12 17:55 16,394
PRM 107.1 7/9/12 18:26 28,409 8/18/12 13:12 15,508 10/4/12 14:10 14,558
PRM 106.1 -- -- -- 8/18/12 14:22 15,278 -- -- --
PRM 105.3 -- -- -- 8/18/12 15:52 15,362 -- -- --
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Project River Mile
High Q Trip Mid Q Trip Low Q Trip
Date Time Discharge Date Time Discharge Date Time Discharge
PRM 104.7 -- -- -- 8/18/12 17:48 15,377 -- -- --
PRM 104.1 -- -- -- 8/19/12 12:49 15,345 -- -- --
PRM 103.5 -- -- -- -- -- -- 10/4/12 16:49 14,575
PRM 102.7 7/10/12 13:53 26,635 -- -- -- -- -- --
PRM 101.4 -- -- -- -- -- -- -- -- --
PRM 98.4 7/11/12 14:09 46,499 8/20/12 14:51 40,623 10/5/12 14:37 39,065
PRM 97.0 7/11/12 18:27 45,118 8/20/12 17:03 40,261 -- -- --
PRM 91.6 8/21/12 14:55 46,330 -- -- --
PRM 91.0 7/12/12 15:39 43,922 8/21/12 16:51 46,197 -- -- --
PRM 88.4 -- -- -- 8/22/12 15:01 41,697 -- -- --
PRM 87.1 7/12/12 18:00 42,550 -- -- -- -- -- --
PRM 86.3 7/13/12 13:13 41,895 -- -- -- -- -- --
PRM 85.4 -- -- -- 8/22/12 18:01 40,468 -- -- --
PRM 84.4 -- -- -- 8/23/12 15:16 36,988 -- -- --
PRM 83.0 7/13/12 16:09 41,975 -- -- -- -- -- --
PRM 82.3 -- -- -- 8/23/12 17:52 37,947 -- -- --
PRM 80.0 -- -- -- 8/24/12 15:07 36,580 -- -- --
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Table 17. Habitat types by geomorphic reach and how representativeness will be achieved. (FA=Focus Area; CS=Cross-section).
Habitat
MR-1 MR-2 MR-5 MR-6 MR-7 MR-8
FA CS NEED FA CS NEED FA CS NEED FA CS NEED FA CS NEED FA CS NEED
Main Channel X
X
X
X
X
X
Split Main Channel n/a
X
X
X
X
X
Braided Main Channel n/a
n/a
n/a
X
n/a
X
Side Channel X
X
X X
X
X
Side Slough n/a
X
X X
X
X
Upland Slough n/a
X
n/a
X
X
X
Beaver Complex n/a
n/a
n/a
X
X X
Backwater n/a
X n/a
X
X
X
Tributary n/a
X
X
X
X
X
Tributary Mouth n/a
X
X
X
X n/a
Clear Water Plume n/a
X
X
X
X n/a
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Table 18. Summary of Potential Effects of With-Project Flows on Tributaries of the Lower Susitna River from 1980s
studies, and tributary mouths proposed for modeling in 2013 (indicated by highlighting) (1980s summary adapted from
Ashton and Trihey (1985)).
Tributary
Project
River
Mile (approx.) Geomorphic Reach
Location of Tributary Mouth in
Effects of With-Project Flows on
Fish Access into Tributaries at 21,000 cfs (USGS Sunshine Gage 15292780)
Reduction in Backwater Area during June/July
Side Channel Main Channel
Potential
Passage Problem
No
Passage Problem
Moderate Change Slight Change
Trapper Cr. 94.5 LR-1 X X X
Birch Cr. 92.5 LR-1 X X X
Sunshine Cr. 88 LR-1 X X X
Rabideaux Cr. 87 LR-2 --- --- X X
Montana Cr. 81 LR-2 X X X
Goose Cr. 76.5 LR-2 X X X
Sheep Cr. 69.5 LR-2 X X X
Caswell Cr. 67 LR-2 X X X
Kashwitna R. 65 LR-3 X X X
Little Willow Cr. 54.5 LR-3 X X X
Willow Cr. 52.5 LR-3 X X X
Deshka R. 45 LR-3 X X X
Alexander Cr. 14 LR-6 X X X
Table 19. List of Lower River 2013 Riparian Vegetation Sampling Transects, and Geomorphic Reach Types (Tetra Tech,
2013d).
Lower River
Geomorphic Reach
Location (PRM)
Riparian
Transect
Riparian Transect
Location (PRM)
Upstream Downstream LR-1 102.4 87.9 RIP LR-1 95.0
LR-2 87.9 65.6 RIP LR-2 69.0
LR-3 65.6 44.6 RIP LR-3 53.5
LR-4 44.6 32.3 RIP LR-4 38.2
LR-5 32.3 23.5 RIP LR-5 30.8
LR-6 23.5 3.3 N/A N/A
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Table 20. Proposed Susitna River Basin Temperature and Water Quality Monitoring Sites.
Susitna River Mile Description Latitude (decimal degrees) Longitude (decimal degrees)
15.1 Susitna above Alexander Creek 61.4014 -150.519
25.83 Susitna Station 61.5454 -150.516
28.0 Yentna River 61.589 -150.468
29.5 Susitna above Yentna 61.5752 -150.248
40.63 Deshka River 61.7098 -150.324
55.01 Susitna 61.8589 -150.18
83.83 Susitna at Parks Highway East 62.175 -150.174
83.93 Susitna at Parks Highway West 62.1765 -150.177
97.0 LRX 1 62.3223 -150.127
97.2 Talkeetna River 62.3418 -150.106
98.5 Chulitna River 62.5574 -150.236
103.02,3 Talkeetna 62.3943 -150.134
113.02 LRX 18 62.5243 -150.112
120.72,3 Curry Fishwheel Camp 62.6178 -150.012
126.0 Slough 8A 62.6707 -149.903
126.12 LRX 29 62.6718 -149.902
129.23 Slough 9 62.7022 -149.843
130.82 LRX 35 62.714 -149.81
135.3 Slough 11 62.7555 -149.7111
136.5 Susitna near Gold Creek 62.7672 -149.694
136.83 Gold Creek 62.7676 -149.691
138.01 Slough 16B 62.7812 -149.674
138.63 Indian River 62.8009 -149.664
138.72 Susitna above Indian River 62.7857 -149.651
140.0 Slough 19 62.7929 -149.615
140.12 LRX 53 62.7948 -149.613
142.0 Slough 21 62.8163 -149.576
148.0 Susitna below Portage Creek 62.8316 -149.406
148.82 Susitna above Portage Creek 62.8286 -149.379
148.8 Portage Creek 62.8317 -149.379
148.83 Susitna above Portage Creek 62.8279 -149.377
165.01 Susitna 62.7899 -148.997
180.31 Susitna below Tsusena Creek 62.8157 -148.652
181.33 Tsusena Creek 62.8224 -148.613
184.51 Susitna at Watana Dam site 62.8226 -148.533
194.1 Watana Creek 62.8296 -148.259
206.8 Kosina Creek 62.7822 -147.94
223.73 Susitna near Cantwell 62.7052 147.538
233.4 Oshetna River 62.6402 -147.383
Notes:
1 Site not sampled for water quality or temperature in the 1980s or location moved slightly from original location.
2 Proposed mainstem Susitna River temperature monitoring sites for purposes of 1980s SNTEMP model
evaluation.
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7. FIGURES
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Figure 1. Map of the Middle Segment of the Susitna River depicting the eight Geomorphic Reaches and locations of proposed Focus Areas. No Focus Areas are
proposed for in MR-3 and MR-4 due to safety issues related to sampling within or proximal to Devils Canyon.
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Figure 2. Map of the Lower Segment of the Susitna River depicting the six Geomorphic Reaches. Focus Areas have not been identified in this segment but will be
considered pending results of open-water flow routing modeling.
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Figure 3. Map showing Focus Area 184 that begins at Project River Mile 184.7 and extends upstream to PRM 185.7. The Focus Area is located about 1.4 miles
downstream of the proposed Watana Dam site near Tsusena Creek.
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Figure 4. Map showing Focus Area 173 beginning at Project River Mile 173.6 and extends upstream to PRM 175.4. This Focus Area is near Stephan Lake and consists
of main channel and a side channel complex.
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Figure 5. Map showing Focus Area 171 beginning at Project River Mile 171.6 and extends upstream to PRM 173. This Focus Area is near Stephan Lake and consists of
main channel and a single side channel with vegetated island.
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Figure 6. Map showing Focus Area 151 beginning at Project River Mile 151.8 and extends upstream to PRM 152.3. This single main channel Focus Area is at the
Portage Creek confluence.
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Figure 7. Map showing Focus Area 144 beginning at Project River Mile 144.4 and extends upstream to PRM 145.7. This Focus Area is located about 2.3 miles upstream
of Indian River and includes Side Channel 21 and Slough 21.
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Figure 8. Map showing Focus Area 141 beginning at Project River Mile 141.8 and extends upstream to PRM 143.4. This Focus Area includes the Indian River
confluence and a range of main channel and off-channel habitats.
Slough 17
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Figure 9. Map showing Focus Area 138 beginning at Project River Mile 138.7 and extends upstream to PRM 140. This Focus Area is near Gold Creek and consists of a
complex of side channel, side slough and upland slough habitats including Upper Side Channel 11 and Slough 11.
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Figure 10. Map showing Focus Area 128 beginning at Project River Mile 128.1 and extends upstream to PRM 129.7. This Focus Area consists of side channel, side
slough and tributary confluence habitat features including Skull Creek.
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Figure 11. Map showing Focus Area 115 beginning at Project River Mile 115.3 and extends upstream to PRM 116.5. This Focus Area is located about 0.6 miles
downstream of Lane Creek and consists of side channel and upland slough habitats including Slough 6A.
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Figure 12. Map showing Focus Area 104 beginning at Project River Mile 104.8 and extends upstream to PRM 106. This Focus Area covers the diverse range of habitats
in the Whiskers Slough complex.
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Figure 13. Percent of main channel in single main, split main, and braided main channel habitat by geomorphic reach
and focus area (F), non-focus area (NF), and total (T).
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Figure 14. Side channel, side slough, and upland slough lengths per mile of main channel by geomorphic reach and focus
area (F), non-focus area (NF), and total (T).
Figure 15. Percent of slough habitat that is in beaver complex by geomorphic reach and focus area (F), non-focus area
(NF), and total (T).
0
0.5
1
1.5
2
2.5
3
3.5
4
F NF T F NF T F NF T F NF T F NF T F NF T
MR-1 MR-2 MR-5 MR-6 MR-7 MR-8Length in Side Habitats/Main Channel Length Upland Slough/Main Channel
Side Slough/Main Channel
Side Channel/Main Channel
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
MR-1 MR-2 MR-5 MR-6 MR-7 MR-8Percent of Slough Habitat in Beaver Complexes Focus Areas
Non Focus Areas
Total
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Figure 16. Backwaters, tributaries, tributary mouths, and plumes density (#/mile) by geomorphic reach and focus area
(F), non-focus area (NF), and total (T).
Figure 17. Percent of main and side channel habitat that is in riffle vs. glide/run habitat by geomorphic reach and focus
area (F), non-focus area (NF), and total (T).
0.0
1.0
2.0
3.0
4.0
5.0
6.0
F NF T F NF T F NF T F NF T F NF T F NF T
MR-1 MR-2 MR-5 MR-6 MR-7 MR-8#/Mile Clearwater Plume Density
Trib Mouth Density
Tributary Density
Backwater Density
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
F NF T F NF T F NF T F NF T F NF T F NF T
MR-1 MR-2 MR-5 MR-6 MR-7 MR-8Percent of Main + Side Channel Riffle
Glide/Run
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Figure 18. Riparian Process Domains on the Middle River with locations of associated Riparian IFS Focus Areas.
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Figure 19. Locations of habitat types missing from the Focus Areas by Geomorphic Reach. Habitat types included split main channel (MR-2, MR-5), side slough (MR-
5), Tributary mouth (MR-7) and backwater (MR-2 and MR-8).
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Figure 20. Map of the Lower Segment of the Susitna River depicting the six Geomorphic Reaches and locations of proposed 2013 study areas for geomorphology,
instream flow–fish, instream flow-riparian and fish distribution and abundance.
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Figure 21. Map showing proposed location of lower Susitna River instream flow-fish habitat transects in Geomorphic Reach LR-1 in the vicinity of Trapper Creek. The
proposed location, number, angle, and transect endpoints are tentative pending on-site confirmation during open-water conditions. Where feasible, instream flow fish
habitat transects will be co-located with geomorphology, open-water flow routing, and instream flow -riparian transects.
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Figure 22. Map showing proposed location of lower Susitna River instream flow-fish habitat transects in Geomorphic Reach LR-2 in the vicinity of Caswell Creek. The
proposed location, number, angle, and transect endpoints are tentative pending on-site confirmation during open-water conditions. Where feasible, instream flow fish
habitat transects will be co-located with geomorphology, open-water flow routing and instream flow -riparian transects.
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Figure 23. Ice Processes Study locations in Lower River.
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Figure 24. Proposed water quality sample locations for Susitna River.