HomeMy WebLinkAboutSuWa207sec11-7Alaska Resources Library & Information Services
Susitna-Watana Hydroelectric Project Document
ARLIS Uniform Cover Page
Title:
Wetland mapping study in the upper and middle Susitna basin, Study plan
Section 11.7 : Initial study report
SuWa 207
Author(s) – Personal:
Author(s) – Corporate:
Prepared by ABR, Inc.-Environmental Research & Services
AEA-identified category, if specified:
Draft initial study report
AEA-identified series, if specified:
Series (ARLIS-assigned report number):
Susitna-Watana Hydroelectric Project document number 207
Existing numbers on document:
Published by:
[Anchorage : Alaska Energy Authority, 2014]
Date published:
February 2014
Published for:
Alaska Energy Authority
Date or date range of report:
Volume and/or Part numbers:
Study plan Section 11.7
Final or Draft status, as indicated:
Draft
Document type:
Pagination:
vi, 31, 1 p.
Related work(s):
Pages added/changed by ARLIS:
Notes:
All reports in the Susitna-Watana Hydroelectric Project Document series include an ARLIS-
produced cover page and an ARLIS-assigned number for uniformity and citability. All reports
are posted online at http://www.arlis.org/resources/susitna-watana/
Susitna-Watana Hydroelectric Project
(FERC No. 14241)
Wetland Mapping Study in the Upper and Middle
Susitna Basin
Study Plan Section 11.7
Initial Study Report
Prepared for
Alaska Energy Authority
Prepared by
ABR, Inc.—Environmental Research & Services
February 2014 Draft
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page i February 2014 Draft
TABLE OF CONTENTS
Executive Summary ...................................................................................................................... v
1. Introduction............................................................................................................................ 1
2. Study Objectives .................................................................................................................... 1
3. Study Area .............................................................................................................................. 2
4. Methods and Variances in 2013 ............................................................................................ 2
4.1. Wetlands Classification and Mapping ........................................................................... 3
4.1.1. Variances................................................................................................................. 5
4.2. Field Surveys .................................................................................................................. 5
4.2.1. Variances................................................................................................................. 7
4.3. Wetland Functional Assessment .................................................................................... 7
4.3.1. Variances............................................................................................................... 11
5. Results ................................................................................................................................... 11
5.1. Wetlands Classification and Mapping ......................................................................... 11
5.2. Field Survey ................................................................................................................. 11
5.2.1. Waters ................................................................................................................... 12
5.2.2. Wetlands ............................................................................................................... 12
5.3. Wetland Functional Assessment .................................................................................. 12
6. Discussion ............................................................................................................................. 13
6.1. Wetland Occurrence and Distribution in the Study Area............................................. 14
6.1.1. Ecoregions............................................................................................................. 14
6.1.2. Waters ................................................................................................................... 15
6.1.3. Wetlands ............................................................................................................... 16
6.2. Wetland Functional Assessment .................................................................................. 18
7. Completing the Study .......................................................................................................... 20
8. Literature Cited ................................................................................................................... 20
9. Tables .................................................................................................................................... 23
10. Figures .................................................................................................................................. 27
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page ii February 2014 Draft
LIST OF TABLES
Table 5-1. Mean Monthly Air Temperature and Cumulative Precipitation for Two Weather
Stations Within the Wetland Mapping Study Area, Susitna-Watana Hydroelectric Project,
Alaska, 2013.1 ....................................................................................................................... 23
Table 5.1-1. Wetlands and Waters Sampled in the Field in 2012 and 2013 and Mapped, as of
Mid-November 2013, in the Wetland Mapping Study Area, Susitna-Watana Hydroelectric
Project.1 ................................................................................................................................. 24
Table 5.3-1. Functional Capacity Index (FCI) Values, Following Magee (1998), for Wetland-
determination Plots on Two Transects (T139 and T182) in the Wetland Mapping Study
Area, Susitna-Hydroelectric Project Area, 2013. .................................................................. 26
LIST OF FIGURES
Figure 3-1. Study Area and Ground-reference Plots Sampled in 2013 for the Wetland Mapping
Study, Susitna-Watana Hydroelectric Study Area. ............................................................... 28
Figure 6.1-1. Preliminary Map of Riverine Waters and Riparian Palustrine Wetlands in the
Denali Corridor, Susitna-Watana Hydroelectric Project, 2013............................................. 29
Figure 6.1-2. Preliminary Map of Lacustrine Waters and Associated Palustrine Waters and
Wetlands in an Area West of the Proposed Project Dam Site, Susitna-Watana Hydroelectric
Project, 2013. ........................................................................................................................ 30
Figure 6.1-3. Preliminary Map of HGM Slope (Fen) Wetlands in the Gold Creek Corridor,
Susitna-Watana Hydroelectric Project, 2013. ....................................................................... 31
APPENDICES
Appendix A: Photographs of Representative Wetland Types Sampled in the Vegetation and
Wildlife Habitat Mapping Study Area, Susitna-Watana Hydroelectric Project, 2013.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page iii February 2014 Draft
LIST OF ACRONYMS, ABBREVIATIONS, AND DEFINITIONS
Abbreviation Definition
ADEC Alaska Department of Environmental Conservation
AEA Alaska Energy Authority
AVC Alaska Vegetation Classification
CIRWG Cook Inlet Regional Working Group
ELS Ecological Land Survey
FCI functional capacity index
FERC Federal Energy Regulatory Commission
GIS geographic information system
HGM hydrogeomorphic
ILP Integrated Licensing Process
ISR Initial Study Report
LRR land resource regions
MLRA major land resource areas
NWI National Wetland Inventory
PM&E protection, mitigation and enhancement
PRM Project River Mile
Project Susitna-Watana Hydroelectric Project
QA/QC quality assurance/quality control
RSP Revised Study Plan
SPD Study Plan Determination
TNW Traditionally Navigable Water
USACE United States Army Corps of Engineers
USFWS Fish and Wildlife Service
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page iv February 2014 Draft
Abbreviation Definition
USR Updated Study Report
WAA wetland assessment area
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page v February 2014 Draft
EXECUTIVE SUMMARY
Wetland Mapping Study in the Upper and Middle Susitna Basin 11.7
Purpose The purpose of the wetland mapping study is to classify, delineate, and map
the wetlands occurring in the inundation zone of the proposed Watana
Reservoir, the area of the proposed Project dam site and associated
infrastructure, and along the corridors of the three possible Susitna-Watana
transmission lines/roads. A wetland functional assessment will also be
conducted to determine the specific functions that the wetlands in the study
area provide.
Status This multi-year study was initiated in 2012. Portions of the study area were
successfully surveyed in 2012 and 2013. Field data collection and the
mapping of wetlands will be completed in the final year of study. The final
study results will be presented in the Updated Study Report (USR).
Study
Components
(1) Classify, delineate, and map wetlands in the Upper and Middle Susitna
River Basin based on field data and current aerial imagery for the study area;
(2) conduct field ground-reference surveys to verify image interpretations and
collect data on wetland functions; and (3) determine and evaluate the
ecological functions of the mapped wetland types to facilitate an assessment
of the relative value of each wetland type in the study area.
2013 Variances There were no variances from the wetlands classification, mapping, or
functional assessment methods as described in the Study Plan (RSP Section
11.7.4).
Steps to
Complete the
Study
As explained in the cover letter to this draft ISR, AEA’s plan for completing
this study will be included in the final ISR filed with FERC on June 3, 2014.
Highlighted
Results and
Achievements
The final acquisition of high-resolution imagery for the study was obtained in
2013. The new imagery, which comprises approximately 55% of the study
area, completes the imagery set needed for the mapping of wetlands for the
Project. A total of 1,271 field plots were sampled in 2012–2013, and 40
National Wetland Inventory (NWI) wetland classes were identified; the field
data indicate that there may be few additional NWI classes in the study area.
Vegetation structure in the wetlands identified in the study area ranged from
mature forests to open, wet herbaceous meadows. The sampled wetlands in
alpine and subalpine physiographic areas were often dominated by dwarf
shrub scrub (moist dwarf shrub and wet sedge-dwarf willow shrub types).
Sampled wetlands in areas of upland physiography were a mixture of black
spruce forests and low to tall scrub types. Sampled wetlands in lowland
physiographic areas were a mixture of black spruce forests, low birch and low
willow shrub scrub, and wet graminoid meadow types. Sampled wetlands in
areas of lacustrine physiography were lakes and lake margins composed of
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page vi February 2014 Draft
Wetland Mapping Study in the Upper and Middle Susitna Basin 11.7
wet sedge marsh and/or wet sedge meadow communities, and wetlands in
riverine physiographic areas were predominantly low to tall, seasonally
flooded shrub scrub types, often dominated by willow and alder. As of the end
of December 2013, approximately 130,000 acres had been mapped, which
represents roughly 23% of the study area. Wetlands data from two transects
sampled in 2013 were used for a preliminary wetland functional assessment
following the Magee methods, which were selected for assessing wetland
functions in the study area in consultation with the U.S. Army Corps of
Engineers, U.S. Environmental Protection Agency, and the U.S. Fish and
Wildlife Service. The results show an expected range of wetland function
among hydrogeomorphic classes and NWI wetland types, but they also
indicate areas in which modifications to the Magee functional assessment
model parameters (as discussed with the agencies noted above) will be needed
to better represent the generally undisturbed functional capacity of wetlands
in the study area.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 1 February 2014 Draft
1. INTRODUCTION
On December 14, 2012, Alaska Energy Authority (AEA) filed its Revised Study Plan (RSP) for
the Susitna-Watana Hydroelectric Project No. 14241 (Project) with FERC, which included 58
individual study plans (AEA 2012). Section 11.7 of the RSP described the Wetland Mapping
Study in the Upper and Middle Susitna Basin. On February 1, 2013, FERC staff issued its study
plan determination (February 1 SPD) for 44 of the 58 studies, approving 31 studies as filed and
13 with modifications. RSP Section 11.7 was one of the 31 studies approved with no
modifications.
In this study, wetlands in the in the Upper and Middle Susitna River Basin (where the Watana
Reservoir and Project infrastructure is proposed) are being identified in the field, classified, and
mapped from aerial imagery. The mapping encompasses the inundation zone of the proposed
Watana Reservoir, the Watana dam site and associated infrastructure, and the three alternative
corridors for the Susitna-Watana transmission lines and access corridor. RSP Section 11.7
provided goals, objectives, and proposed methods for data collection regarding wetlands.
Following the first study season, FERC’s regulations for the Integrated Licensing Process (ILP)
require AEA to “prepare and file with the Commission an initial study report describing its
overall progress in implementing the study plan and schedule and the data collected, including an
explanation of any variance from the study plan and schedule” (18 CFR 5.15(c)(1)). This Initial
Study Report (ISR) on the Wetland Mapping Study in the Upper and Middle Susitna Basin has
been prepared in accordance with FERC’s ILP regulations and details AEA’s status in
implementing the study, as set forth in the FERC-approved RSP (referred to herein as the “Study
Plan”).
2. STUDY OBJECTIVES
The overall goal of the wetland mapping study is to prepare a map of existing wetland habitats in
the Upper and Middle Susitna River Basin (upstream of Gold Creek; see Section 3, Study Area,
below). This multi-year study was initiated in 2012. The mapping information from this study
eventually will be used in AEA’s License Application to assess the potential impacts to wetland
resources from development of the proposed Project, and to prepare protection, mitigation, and
enhancement (PM&E) measures, as appropriate, to minimize impacts to wetland resources.
As described in RSP Section 11.7.1.1, the study objectives are to:
• Classify, delineate, and map wetlands in the Upper and Middle Susitna River Basin based
on current aerial imagery for the study area; and
• Determine and evaluate the ecological functions of the mapped wetland types to facilitate
an assessment of the relative value of each wetland type in the study area.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 2 February 2014 Draft
3. STUDY AREA
As established by RSP Section 11.7.3 and depicted in Figure 11.7-1 of the RSP, the study area
comprises a 2-mile buffer surrounding those areas that would be directly altered or disturbed by
development of the proposed Project (
Figure 3-1), including the three alternative corridors for the Susitna-Watana transmission lines
and access road, Watana Dam, and Watana Camp sites, and maximum normal pool elevation of
the Watana Reservoir (2,050 ft). The Chulitna Corridor runs east-west north of the Susitna River
connecting to the Alaska Intertie and the Alaska Railroad near Chulitna station at Chulitna Pass.
Another east-west alternative, the Gold Creek Corridor, runs south of the Susitna River to the
Alaska Intertie and the Alaska Railroad at Gold Creek station. A third alternative, the Denali
Corridor, runs north-south, and would connect the Project dam site with the Denali Highway
over a distance of about 44 miles and then would run west along the existing Denali Highway to
connect to the Alaska Intertie near Cantwell.
In areas paralleling the Susitna River between the Project dam site and Gold Creek station
(Figure 3-1), wetlands within the 2-mile study area buffer will be mapped up to the boundary of
the study area for Riparian Vegetation Study Downstream of the Proposed Susitna-Watana Dam
(Study 11.6). In the riparian vegetation study, successional vegetation, wetlands, and wildlife
habitats will be mapped (i.e., wetlands in riparian areas downstream of the Project dam site along
the Susitna River will be mapped). Mapping methods in the wetland mapping study and riparian
vegetation study are compatible, and a seamless wetlands map for the Project will be produced,
which will include the areas above and below the Project dam site. The alteration of wetland
habitats downstream of the Project dam site (due to changes in instream flow,
groundwater/surface water interactions, ice processes, and fluvial geomorphic features in the
Susitna River) will be addressed in the riparian vegetation study. No placement of fill in
wetlands is expected to occur downstream from the Project dam site; thus, a wetlands map will
not be needed for the Clean Water Act Section 404 wetlands permit application for the Project
(this has been confirmed by the U.S. Army Corps of Engineers [USACE]; see Section 11.7 in
AEA 2012).
4. METHODS AND VARIANCES IN 2013
The wetlands classification and mapping methods are set forth in RSP Section 11.7.4 and include
the following components:
• Preselect field sampling locations and conduct field wetland determination and functional
assessment surveys;
• Conduct wetlands mapping using data collected during field surveys in summer 2012 and
2013;
• Revise the preliminary wetlands mapping using field data collected each year; and
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 3 February 2014 Draft
• Incorporate wetland functional assessment data (see below) into the classification of
wetland types so that the mapped wetlands, whenever possible, represent wetland
functional types.
In addition to preparing a wetlands map for the Project, a wetland functional assessment for the
mapped wetland types is being conducted. As agreed to with resource management agencies (see
RSP Section 11.7.4.3), the set of wetland functions to be assessed for the Project is being tailored
to reflect those expected to be of most importance in remote regions of Alaska where landscape
disturbances are few. The wetland functional assessment is being conducted using
hydrogeomorphic (HGM) principles following the methods of Magee (1998), with modifications
for the largely undisturbed wetland types in the study area and additions of spatially explicit data
indicating specific wetland functions in different portions of the study area (see Section 4.3,
Wetland Functional Assessment, below).
4.1. Wetlands Classification and Mapping
The wetland mapping study team implemented the methods as described in the Study Plan with
no variances.
The methods for classifying and mapping wetlands and waters in the study area were
implemented as described in RSP Section 11.7.4. The mapping, which is a multi-year effort to
cover the entire study area, is being conducted following the protocols for preparing wetland
maps that have been developed by the U.S. Fish and Wildlife Service (USFWS) National
Wetlands Inventory (NWI) program (National Wetlands Inventory Center 1995, Dahl et al.
2009). These protocols describe requirements for boundary delineation, polygon size,
classification, and NWI annotation.
Additional attributes being assigned to wetland polygons include HGM (Brinson 1993) and
Viereck et al. (1992) Level IV vegetation types, which involves incorporating landscape,
geomorphic (physiography and surface form), disturbance, hydrological, and biological variables
into the wetlands map, as well as the presence or absence of permafrost. This integrated
classification approach is similar to a regional classification system developed for lowlands in
the Cook Inlet basin (Gracz 2011), which improves upon Cowardin et al. (1979) by incorporating
region-specific landscape, geomorphic, and wetland functions into the classification of wetlands,
and thus will allow cross-referencing between the two classifications in cases where similar
(lowland) wetland types are identified with the two approaches. This integrated approach to the
classification of wetlands was agreed to during meetings with resource management agencies
regarding the wetland mapping study in spring 2012 (see RSP Section 11.7.4.3). The Cook Inlet
wetland classification system is specific to Cook Inlet lowlands, however, and many wetland
types in the study area (which largely occur at higher elevations) are unlikely to be represented in
the Cook Inlet classification. Developing Project-specific wetland types in this study will allow
the accurate classification of higher-elevation wetlands as well as the cross-referencing of
applicable lowland wetlands to similar types defined in the Cook Inlet classification system.
The wetlands mapping is being prepared by digitizing polygons on-screen using ArcGIS
software. Map polygon boundaries are being determined by interpreting high-resolution (0.3- to
1-ft pixels) aerial image-signatures supported by ground-reference survey data collected in 2012
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 4 February 2014 Draft
and 2013. Wetlands and waters are being mapped at a scale of 1:2,000. The minimum mapping
polygon size for most upland and wetland habitats is 0.5 acres, with smaller polygons (0.1 acre)
delineated for water bodies and other wetlands of ecological importance. Wetland and upland
boundaries are being delineated based on color signature, plant canopy, and surface relief, along
with hydrological indicators such as drainage patterns and surface water connections. Field
parameters being used to assist the mapping effort include vegetation structure, soil organic
matter content, hydrologic regime, electrical conductivity, pH, presence of a restrictive layer
(lack of soil permeability), physiography, and geomorphic characteristics such as macro- and
microtopography, slope, aspect, and surface form.
To assist the wetland functional assessment (see Section 4.3 below), HGM classes are being
assigned to each wetland polygon based on geomorphic position and hydrologic characteristics,
as defined by Brinson (1993) and modified by Smith et al. (1995). Functions and ecological
services provided by wetlands vary by geomorphic position and hydrology, and HGM
classification helps identify differences in both specific functions and their magnitude. For
example, a depressional wetland has a much greater capacity to retain sediment than a slope
wetland, due to its closed or semi-enclosed contours (a slope wetland lacks closed contours).
Thus, while these systems may share a similar NWI wetland class, the difference in HGM class
can be used to distinguish their functional characteristics.
The Level IV vegetation classes of the Alaska Vegetation Classification (AVC; Viereck et al.
1992), with additions by the botanical study team for undescribed types and nonvegetated land
cover types, are defined by vegetation structure and dominant plant species (e.g., Open White
Spruce Forest, Closed Tall Alder Shrub, Subarctic Lowland Sedge Wet Meadow). Physiography
types represent broad, landscape-scale geomorphic features and landscape position (e.g.,
riverine, lacustrine, lowland, upland, subalpine, and alpine). Surface forms are finer scale
geomorphic features, in this case in boreal forest environments (e.g., ridge crest, toe slope, kettle
basin, point bar); the surface-form classes being used were modified from Washburn (1973) and
Jorgenson et al. (2003). The disturbance types being used were modified from a list defined by
the botanical study team for previous Ecological Land Survey (ELS) studies in both remote and
developed areas in Alaska (see Jorgenson et al. 2003 for an example).
Because fine-scale mapping of wetland boundaries is possible only with the use of high-
resolution imagery, the detailed mapping of wetland types prior to the 2013 field season was
limited to two areas for which high-resolution imagery was available: (1) a corridor around the
Upper Susitna River, which covers the southwestern portion of the Watana Reservoir, and
portions of the Gold Creek Corridor; and (2) in the vicinity of Cantwell and adjacent portions of
the Parks and Denali highways in the Denali Corridor. For the areas lacking high-resolution
imagery prior to the 2013 field season, moderate-resolution RapidEye imagery (5-m [16-ft]
pixels), in a false natural-color format, was used to determine preliminary NWI and HGM
wetland classes and select field sampling transects for survey work in 2013. Additional high-
resolution imagery, for those portions of the study area where only moderate-resolution imagery
exists, was acquired by AeroMetric (now Quantum Spatial) in July–August 2013; this new
digital imagery was prepared in both natural color and infrared formats.
The preliminary mapping described above is currently under revision so that it accurately reflects
the field-verified occurrences of NWI and HGM wetland types, Level IV vegetation types,
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 5 February 2014 Draft
physiography, surface form, and disturbance types. Mapping is also being extended into portions
of the study area without preliminary mapping. For this report, a preliminary set of wetland types
(NWI classes only) for the study area was compiled from the mapping that was completed as of
mid-November 2013.
When the wetlands map is completed, the mapping will undergo a rigorous QA/QC review
process using tools developed by the botanical study team and the Wetlands Data Verification
Toolset developed by the NWI program to identify digitizing anomalies (e.g., incorrect attribute
codes, unattributed polygons, adjacent polygons with the same coding, digital slivers [null
polygons < 0.01 acre in size]). The NWI toolset was created using the Environmental Systems
Research, Incorporated (ESRI) ModelBuilder (http://www.fws.gov/wetlands/Data/Tools-
Forms.html).
4.1.1. Variances
In 2013, there were no variances from the wetlands classification and mapping methods
described in RSP Section 11.7.4.1.
4.2. Field Surveys
AEA implemented the methods as described in the Study Plan (RSP Section 11.7.4.2) with the
exception of variances explained below (Section 4.2.1). To link aerial-image signatures with
ground data, eight scientists (four teams of two each) collected wetlands, vegetation, and wildlife
habitat ground-reference data in two separate field survey efforts: July 2–11, 2013 and July 30–
August 8, 2013. These periods are well within the median dates of the onset of vegetation green-
up in spring and vegetation senescence in fall for Southcentral Alaska, as specified in the
Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Alaska Region
(Version 2.0) (USACE 2007). The wetland field surveys were organized so as to collect data for
as many wetland types as possible in a way that maximizes efficiency (numerous different
wetland types were sampled in a day) and safety (topographic hazards such as traversing steep
bluffs and creek crossings were avoided).
A preliminary map of wetland and upland boundaries in those areas where high-resolution
imagery was available was not fully completed prior to the 2013 field season, but the portion of
the mapping completed was used to define a set of characteristic wetland types that occur in the
mapped areas. This information was used to guide the field survey efforts in 2013. The sampling
transects (1.5–3.0 km [0.93–1.86 mi] long) focused on wetland types that were (1) less well
represented in the preliminary mapping; (2) more challenging to identify from aerial image-
signatures; (3) represented by a continuum of aerial image-signatures; and/or (4) under-sampled
during the first year of field surveys (2012). Survey transects were designed to sample a number
of different habitats during each survey day; consequently, transects typically had a number of
vertices. On each transect, 6–10 wetland-determination plots were sampled depending on the
length of the transect and/or the number of distinct habitat types encountered. Field plots were
sampled along transects located within the major physiographic types in the study area, including
riverine, lacustrine, lowland, upland, subalpine, and alpine areas. When transitional habitats or
areas not readily discernible from image-signature features alone were encountered in the field,
additional wetland-determination plots were surveyed.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 6 February 2014 Draft
Wetland determinations were made using the standard three-parameter approach described in the
1987 Corps of Engineers Wetlands Delineation Manual (Environment Laboratory 1987) and the
2007 Regional Supplement (USACE 2007). To be classified as a wetland, a site must be
dominated by hydrophytic plants, have hydric soils, and show evidence of a wetland hydrologic
regime. At each wetland-determination plot, the percent areal cover of each vascular plant
species within each stratum (herb, shrub, and tree) was visually estimated, generally within a 10-
m (33-ft) radius plot of relatively homogeneous vegetation as specified in Environmental
Laboratory (1987). The size and shape of the wetland-determination plots were modified as
needed, however, depending on the extent of the plant community being sampled (e.g., narrower
plots were used in riparian fringe habitats). The presence of hydrophytic vegetation was
determined using the Dominance Test (ratio of wetland versus upland dominant plants) and/or
the Prevalence Index (weighted average of all species present), using the wetland indicator status
for each plant species as listed in the 2013 National Wetland Plant List (Lichvar 2013).
Additional vegetation information (percent areal cover data for structural classes of vascular and
nonvascular plants [trees, saplings, tall shrubs, low shrubs, dwarf shrubs, tall herbs, low herbs,
floating aquatics, submergents, mosses, and lichens]) was recorded to assist in defining wetland
types and evaluating the use of wetland types by birds, mammals, and amphibians.
Hydric soils form under conditions of saturation, flooding, or ponding long enough during the
growing season to develop anaerobic conditions in the upper 12 in of the soil. Hydric soils often
have thick organic deposits (histosols, histels, or histic epipedons) or have a low-chroma mineral
soil matrix color with redoximorphic features, indicating a reducing environment. Soil pits were
excavated to approximately 18 inches or to the depth of the active layer, if shallower, and the soil
profile was described. Key characteristics including color (Munsell Soil Color Charts 2009) and
abundance of redoximorphic features were recorded. Soil profile descriptions also were
compared with hydric soil criteria in the most current version of the Field Indicators of Hydric
Soils in the United States (USDA-NRCS 2010).
Wetland hydrology is defined as the presence of flooded or ponded surface water or saturation
within the upper 12 inches of the soil profile for at least 14 consecutive days during the growing
season at a minimum frequency of 5 years out of 10. Surface and subsurface, direct and indirect
indicators of wetland hydrology were recorded at each site, including surface water, saturated
soils, presence of and depth to water table, drift or sediment deposits, drainage patterns, and
geomorphic position, as summarized in the 2007 Regional Supplement (USACE 2007).
A mobile Trimble® Nomad™ series geographic information system (GIS) unit was used to
record the field data for each wetland-determination plot (using the WetForm database), and to
record global positioning system (GPS) coordinates for each plot. WetForm is a relational
database used to record wetlands site data in the field, and it facilitates the preparation of
electronic copies of the 2007 Regional Supplement dataform (USACE 2007) for each wetland
determination plot.
Additional data recorded at each wetland-determination plot to support the wetland classification
and wetland functional assessment included HGM wetland class; AVC Level IV vegetation
class; physiography class; disturbance class; slope and aspect (in degrees); site, vegetation, and
soil photos; and GPS coordinates. Observations of recreational use, subsistence use, and wildlife
use (e.g., nests, dens, scat, tracks) and other site characteristics that reflect habitat quality and
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 7 February 2014 Draft
wetland function also were recorded at each plot (see Section 4.3, Wetland Functional
Assessment, below). These data were recorded using a customized data-entry program on an
Android tablet computer.
In addition to the formal wetland-determination plots, rapid map-verification plots were sampled
to help facilitate the wetlands mapping effort. Map-verification plots were sampled in habitats
for which the wetland or upland status had been previously well documented with full wetland-
determination plots at other sites; the map-verification plots were used to improve map accuracy
by increasing the number of documented wetland types tagged to particular aerial image-
signatures. At these plots, a limited set of data was recorded, including cover estimates for the
dominant vascular plant species, HGM wetland class, the Cowardin et al. (1979) water regime
class, AVC Level IV vegetation class, physiography class, site photos, and GPS coordinates. No
soils information was recorded at map-verification plots.
To support the survey efforts of other botanical and wildlife studies being conducted for the
Project, the locations of all incidental observations of rare plants, invasive plants, wildlife
species, wildlife use (e.g., browsed plants) or significant wildlife habitat features (e.g., raptor
nests) were documented when encountered.
4.2.1. Variances
In 2013, there were no variances from the field sampling methods described in RSP Section
11.7.4.2. This study was designed with a multi-year data collection effort and no specific
sampling locations were identified in RSP Section 11.7.4.2. The sampling of wetland
determination plots in 2013 was restricted to accessible lands (state, federal, and Ahtna, Inc.
lands). Consequently, thus far, some wetland types in the study area have not yet been sampled
or are under-sampled, such as low-elevation slope wetlands above the Susitna River, wetlands in
the Fog Lakes area, and at the northern end of Stephan Lake, all of which occur on Cook Inlet
Regional Working Group (CIRWG) lands. If access to CIRWG lands is granted for the next year
of study, the wetland types occurring on these lands can be adequately described and the study
objectives can be achieved.
4.3. Wetland Functional Assessment
AEA implemented the wetland functional assessment methods as described in the Study Plan
(RSP Section 11.7.4.3) with no variances. Based on agreements reached with resource
management agencies while planning the wetland mapping study (see Section 11.7 in AEA
2012), the ecological functions of wetlands in the study area are being assessed using HGM
principles (Smith et al. 1995). Several draft HGM guidebooks have been prepared for the Cook
Inlet Basin (Hall et al. 2003) and Interior Alaska (ADEC and USACE 1999), but the models are
confined to a small set of HGM classes (primarily slope and flat wetlands in lowland boreal
forest regions) and are regionally specific. Consequently, those models do not apply to all the
wetland classes in the Susitna River Basin, which lies in a transition zone between Interior
Alaska and Cook Inlet, and includes montane and riverine environments in addition to boreal
forest wetlands. Instead, the rapid assessment procedure developed by Magee (1998), which is
based on HGM wetland classes, is being used as the basis for assessing wetland functions for this
study, but the procedure and parameters measured will be modified as needed to evaluate
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 8 February 2014 Draft
wetland functions unique to the study area. As in formal HGM classifications, HGM wetland
classes, as defined by Brinson (1993) (e.g., depressional, slope, lacustrine fringe), are being
assigned to each mapped wetland type. The functional capacity of each wetland type is being
assessed based on an extension of Magee’s (1998) rapid-assessment procedure (hereafter
referred to as the Magee model), which involves incorporating field data into HGM-specific
wetland-function models. In the field, the wetland functional assessment data needed for the
model were collected electronically using a customized data-entry program on an Android tablet
computer.
The primary components of the Magee portion of the model are the wetland assessment area
(WAA), the eight Magee wetland functions, and the functional capacity index (FCI) for each
wetland type. FCI values are calculated using either direct measurement of wetland function or
using field data for a suite of variables that apply to each of the eight standard Magee functions
within individual WAAs (see below). In small-sized wetland projects, the WAA often represents
an individual wetland type with associated ground-reference data, but for large-sized mapping
projects based on aerial image-interpretation, the WAA needs to be a representative wetland type
that can be reliably recognized on aerial imagery. In the analysis, FCI values are calculated for
areas with ground-reference data and then extrapolated to similar mapped types in the study area.
The Magee model is used initially to calculate FCI values for the eight standard Magee functions
(listed below) for each plot sampled in the field, so that during the initial analysis stages the
wetland assessment area (WAA) represents only one wetland type. To establish wetland
functional classes (sets of wetland types that share similar wetland functions), iterative runs of
the Magee model are used and wetland types are then grouped into functional classes. As model
development proceeds in the next study season using the full set of mapped wetland types in the
study area, the wetland functional classes, not individual wetland types, will be considered as the
WAAs. At that stage, representative FCI values for each of the eight Magee functions will be
assigned to each wetland functional class mapped in the study area.
Once the Magee portion of the functional assessment is complete, project-specific GIS data
layers prepared by other AEA researchers working on the Project will be used to assess two
additional wetland functions not included in the Magee model (consumptive uses and
uniqueness), and to improve the functional assessment information for a third function (fish and
wildlife habitat). Using a GIS-based approach to build on a standard wetland functional analysis
has the advantage of providing spatially explicit information on wetland functions in different
parts of the study area, which is quite large and covers portions of three different ecoregions of
the state (see Section 6.1.1, Ecoregions, below). The full wetland functional assessment cannot
be completed until after the wetlands mapping is complete and the final Project-specific data
layers from other researchers are available (see below).
In the full functional assessment, the following set of 10 wetland functions will be evaluated
using a combination of field data from this and other Project studies. As noted above, eight
functions will be assessed following the methods of Magee (1998). Two additional functions will
be assessed using spatially explicit GIS analyses of the occurrence of individual wetland
functional classes mapped in the study area, and one of the 10 functions will be assessed using a
combination of Magee model results and GIS analyses:
• Modification of groundwater discharge (Magee)
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 9 February 2014 Draft
• Modification of groundwater recharge (Magee)
• Storm and flood-water storage (Magee)
• Modification of stream flow (Magee)
• Modification of water quality, including sediment retention and nutrient and toxicant
removal (Magee)
• Export of detritus (Magee)
• Contribution to abundance and diversity of wetland vegetation (Magee)
• Fish and wildlife habitat (Magee and GIS analysis)
• Consumptive uses (GIS analysis)
• Uniqueness (GIS analysis)
At each wetland-determination plot sampled in the field, data reflecting wetland functional
capacity were collected for hydrologic variables (surface water pH, electrical conductivity,
wetland water regime, presence of seeps or springs, surface water fluctuations, surface water
interspersion), soil variables (permeability, sedimentation), vegetation variables (dominant
wetland type, areal cover of dominant vegetation, vegetation interspersion, dominant plant
dispersion), and site variables (landscape-scale topographic gradient, microtopographic relief,
site size, site connectivity) following Magee (1998). As described above, the collected data will
be run through the Magee model to determine a base level of functional capacity (FCI value) for
each mapped wetland type for 8 of the 10 functions (all except consumptive uses, and
uniqueness). In this process, the data for the wetland function variables that apply to each of the
eight standard Magee wetland functions are combined and summarized to derive FCI values for
each mapped wetland type, as described by Magee (1998). Due to the large size of the study
area, it was not feasible to deploy piezometers in each wetland type to collect direct information
on two wetland functions (Modification of Groundwater Discharge and Modification of
Groundwater Recharge). Instead, field observations were used to make inferences regarding
groundwater discharge and recharge as described by Magee (1998), and those field variables will
be used to derive FCI values for the discharge and recharge functions. Through an iterative
process beginning with analyses based on field plot data for individual wetland types, the
wetland function model will be adjusted to provide FCI values for each wetland functional class
mapped in the study area. Then, using Project-specific GIS data, consumptive uses and
uniqueness will be evaluated and the model results for the fish and wildlife habitat function will
be augmented, as described below.
The fish and wildlife and habitat functions will initially be assessed using the Magee model, and
then in a spatially explicit way by incorporating Project-specific fish and wildlife occurrence
data to indicate which specific wetlands in the study area provide those habitat functions and to
what degree. Fish-occurrence data for the study area, from the Fish Distribution And Abundance
Studies (Studies 9.5 and 9.6) and the Fish Habitat Study (Study 9.9), will be used to attribute
individual wetland (water body) polygons known to support fish, which will then be given higher
rankings for the fish habitat function. The fish-habitat rankings will be determined based on the
number of fish species and life-history stages present, so that water bodies supporting more
species and a greater number of life-history stages will be ranked higher. Data from the wildlife
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 10 February 2014 Draft
studies, including large mammals (Studies 10.5 through 10.8), furbearers (Studies 10.9 through
10.11), small mammals (Study 10.12), bats (Study 10.13), birds (Studies 10.15 through 10.17),
and amphibians (Study 10.18) will be used to identify habitat features important for particular
species of birds, mammals, and amphibians, and to identify specific regions in the study area that
are heavily used by wildlife. This information then will be used to evaluate the use of the
mapped wetland types by wildlife; this will entail conducting habitat-use evaluations for wetland
types instead of habitat-use evaluations for wildlife habitat types (as will be done in the
Evaluation of Wildlife Habitat Use; Study 10.19). Wetlands known or expected to support
wildlife will then be given a higher functional capacity index for wildlife habitat. As with the
fish-habitat function, those wetlands that support a greater number of wildlife species and more
life-history stages will be ranked higher.
Magee (1998) does not include models for consumptive uses or uniqueness. If possible, the
evaluation of the consumptive uses function will be spatially explicit, using Project-specific
recreational- and subsistence-use data (see Studies 12.5 and 14.5, respectively) to indicate which
general regions in the study area are used currently (actual use for recreation and subsistence
activities such as hunting, trapping, fishing, berry picking). The coarse spatial resolution of the
recreational- and subsistence-use data, however, likely will preclude a determination of which
specific wetland types are being used, so a likelihood of actual use will be assigned based on the
vegetation structure and plant species composition in each wetland type and proximity to access
points for recreational and subsistence users. The potential for additional consumptive use in
other parts of the study area after Project construction will be assessed in GIS by identifying
those wetland types that are likely to be used now, as described above, and then determining the
locations of those types where they occur adjacent to the three proposed alternative transmission
lines and access road alignments. Those wetland areas that could be more easily accessed via a
new road will be categorized with a potential consumptive use value specific to the possible
future use(s).
The specific definition of wetland uniqueness will be determined after the mapping of wetland
types in the study area is completed. The uniqueness function will be used to identify those
wetland types and their specific occurrences in the study area that are regionally scarce relative
to other more common wetland types.
The study area lies within zones of discontinuous and sporadic permafrost (Brown et al. 2001),
and permafrost is known to affect the functional capacity of wetlands (e.g., by slowing
biogeochemical reaction rates due to low temperatures and reducing groundwater recharge). The
presence or absence of permafrost is included in the classification of wetland types (see Section
4.1, Wetland Classification and Mapping, above), thus allowing distinctions between the
functional capacities of permafrost and non-permafrost wetland types.
For review in this report, FCI values were calculated and preliminary wetland functional classes
were derived for the field data for two example field transects. Plots along transects T139 and
T182 were given FCI values for the eight standard Magee functions using data collected from
each field plot and the plots were then grouped into preliminary wetland functional classes. The
wetland functional assessment will be finalized in the USR, after additional field data are
collected and the mapping of wetlands is completed for the full study area.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 11 February 2014 Draft
4.3.1. Variances
In 2013, there were no variances from the wetland functional assessment methodology described
in RSP Section 11.7.4.3.
5. RESULTS
5.1. Wetlands Classification and Mapping
Mapping of wetlands in the study area was initiated in 2012 and will continue over the course of
the study. As of the end of December 2013, approximately 130,000 acres had been mapped,
which represents roughly 23 percent of the study area. High-resolution imagery that was not
available for portions of the study area in 2012 was rectified in 2013 with the acquisition of two
new sets of imagery. The first is archived satellite imagery from the QuickBird-2, WorldView-2,
and Pleiades 1 satellites acquired in 2010–2012. Acquisition dates for those images were
between July 7 and August 14, and the imagery was processed in both natural color and color
infrared formats to create a 0.5 m (1.6 ft) orthomosaic. The remaining image gaps were filled
with digital aerial imagery (0.5 m [1.6 ft] resolution) acquired by AeroMetric (now Quantum
Spatial) in July 2013. This imagery also was processed in both natural color and color infrared
formats.
To support the wetland mapping efforts, a total of 40 NWI wetland types were assigned to field
plots sampled in the study area in 2012 and 2013 (Table 5.1-1). The NWI types were determined
using plot-specific plant species cover and hydrology data. As the number of sampled plots
increases, the set of NWI types documented increasingly should represent the range of variation
within the image-signatures of wetland types in the study area. Given the small increase in new
NWI types recorded in the 2013 field season, the current list of NWI types is likely to be a good
estimate of the actual number of NWI types found in the study area. During the mapping efforts
in the next year of study, close comparisons of the data for individual field plots that share
similar image-signatures will eventually result in a list of those wetland types that can be reliably
recognized and mapped versus those that represent features that are typically either below the
minimum map size or that cannot be reliably tagged to a specific image-signature. As the
mapping proceeds in the next year of study, a final list of wetland functional classes will be
determined based on field data, the mapping of wetland types, and the results of the wetland
functional assessment. As noted above, final wetland functional classes cannot be developed
until further mapping, additional data QA/QC, and a full set of wetland functional assessment
model runs are completed.
5.2. Field Survey
In 2013, a total of 914 field plots were sampled along 77 transects (Figure 3-1). Standard
USACE field wetland determinations were completed at 619 wetland-determination plots and
map-verification data were collected at 295 plots. Of the 619 wetland-determination plots, 379
were located in waters or wetlands and 240 were in upland areas (Table 5.1-1).
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 12 February 2014 Draft
Two weather stations closest to the study area indicated that temperatures during the 2012 field
season were near average (Table 5-1). Because of the unusually late, cold spring in 2013,
temperatures were cooler than the 30-year mean in April and May, but then were above the long-
term averages for the remainder of the field season. Precipitation was more than double the 30-
year mean at the Chulitna River station in June 2012 and May 2013, and nearly double that at the
Cantwell 4E station in June 2012. Precipitation for the remaining months of the 2012 and 2013
growing seasons, however, was well below the 30-year mean.
5.2.1. Waters
Waters of the U.S. were frequently sampled within the riverine, lacustrine, and palustrine
systems in the study area; five riverine types, two palustrine types, and one lacustrine type were
recorded in 2012 and 2013 (Table 5.1-1). Riverine waters fell into intermittent, lower perennial,
and upper perennial systems. The two largest rivers in the study area (the Susitna and Nenana
rivers) are classified as upper perennial (R3UBH) and accounted for the majority of field plots
within that type. Permanently flooded ponds (PUBH and PUBHb) were sampled frequently
throughout the study area, whereas larger lakes (L1UBH) were less commonly sampled.
5.2.2. Wetlands
Over the 2 years of field study, 32 palustrine, terrestrial, and vegetated wetland types were
sampled (Table 5.1-1). The most commonly sampled NWI wetland type was saturated broadleaf
deciduous shrub-scrub (PSS1B). This is in part due to the widespread distribution of this type in
the study area, but is also due to the wide range of plant communities that occur in the PSS1B
type and a sampling design focus on this particular wetland type in 2013. Other commonly
sampled types include wet emergent meadows such as semi-permanently flooded persistent
emergent (PEM1F) and seasonally flooded/saturated persistent emergent (PEM1E). In general,
saturated shrub-dominated communities were sampled more often than emergent (herbaceous-
dominated) wetland types . Emergent types tended to have wetter hydrology; often they were
permanently flooded or semi-permanently flooded, whereas shrub-dominated communities
tended to have only saturated hydrology.
5.3. Wetland Functional Assessment
Two transects (T139 and T182) that were sampled in 2013 were selected for the preliminary
wetland functional assessment model run presented in this report. Transect T139 is located on a
north-facing upland bench above the Susitna River near Gold Creek. The transect traverses
undulating terrain with open, mixed forest non-wetlands on well-drained convex surfaces and
slope wetland complexes occurring in the intervening low-lying troughs, which were formed by
glacial scour. Transect T182 is located on a north-facing slope just above treeline in the
subalpine zone, west of the confluence of the Susitna River and Deadman Creek. The wetland
types crossed on this transect include seasonally flooded/saturated meadows and saturated,
sloping shrub-dominated wetlands.
On these two transects, one HGM riverine wetland type (PSS1C) was recorded on plot T139_06,
while the remaining wetlands were classified as HGM slope types (Table 5.3-1). Saturated
wetland types (PFO4B and PSS4/3B) were recorded at two plots and the remaining wetland
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 13 February 2014 Draft
types were classified as seasonally flooded/saturated (PEM1E) or semi-permanently flooded
(PEM1F).
Of the wetland functions assessed, groundwater discharge is the dominant hydrology source for
HGM slope wetlands. Because groundwater discharge and recharge are mutually exclusive
functions, slope wetlands are unlikely to contribute to groundwater recharge, and Magee’s
(1998) models do not evaluate groundwater recharge for HGM slope wetlands. Hence, the
groundwater recharge function was not assessed for slope wetlands; all other functions were
evaluated for each wetland type on each plot (Table 5.3-1).
Magee’s (1998) models often use the characteristics of channelized features within a wetland to
infer functional capacity. For example, a wetland with no channelized inlet but a perennial
channelized outlet can be inferred to perform groundwater discharge; thus, this combination of
inlet/outlet class would be given an FCI of 1 for groundwater discharge. The HGM riverine
wetland on Transect T139 was assigned inlet and outlet classes consistent with an active channel
(perennial river inlets and outlets). The wetter HGM slope wetlands (seasonally flooded/
saturated and semi-permanently flooded) that were assessed were closely associated with
perennial channelized features as observed in the field. In contrast, the saturated slope wetlands
(PFO4B, PSS1B, and PSS4/3B) had no inlets or outlets unless they were immediately adjacent to
a broader wetland complex containing flooded wetland types. The large size of many wetland
complexes within the study area and the need for efficient field data collection precluded
walking the perimeter of every observed wetland to determine inlet and outlet class. Where there
were no field observations of channelized features, aerial imagery was reviewed and all visible
channelized features identified were assumed to be perennial. The wetter slope wetlands with no
visible channelized features were assumed to have intermittent inlets and outlets based on the
prevalence of small channels observed in these wetland types in the field.
A number of the broad, landscape-scale Magee variables were assessed in the office either by
image interpretation in GIS, as with the inlet outlet classes discussed above, or by making
reasonable assumptions that apply to the entire study area. For example, the ratio of wetland area
to watershed area was assessed in GIS based on the mapping completed as of mid-November
2013, and for the wetland land use variable, it was assumed that current land use is low intensity
for every sample plot in the study area, which is relatively remote and infrequently visited by
humans.
Data developed in support of this study are available for download at
http://gis.suhydro.org/reports/isr. The data are in two files:
• Field data, plot locations, and wetland classification data for plots in the example map
areas: ISR_11_7_WET_Plot_and_Classif.gdb
• GIS polygon data for the example map areas: ISR_11_7_WET_Data_ABR.gdb
6. DISCUSSION
The wetland mapping study is currently on-going, including QA/QC of the field data, aerial
imagery interpretation and mapping of wetlands, and wetland functional assessment analysis.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 14 February 2014 Draft
The field data collection and mapping efforts in 2013 were performed with no variances (see
Section 4, above), and although QA/QC is ongoing, all indications are that data are of sufficient
quality to meet study objectives. A discussion of the status of the specific study components,
including interrelated studies, is presented below.
6.1. Wetland Occurrence and Distribution in the Study Area
6.1.1. Ecoregions
Land resource regions (LRRs) and major land resource areas (MLRAs) in Alaska were defined
by the USDA-NRCS (2004) using climatic, physiographic, biological, and ecological features,
properties, and relationships. LRRs represent broad regions of the state that share similar
climatic conditions, patterns, and processes, and MLRAs represent subregional areas with shared
physiographic and geomorphic patterns and processes. MLRAs were used as the basis for the
subregions employed in the National Wetland Plant List (Lichvar 2013), which is being used in
this study. The wetland mapping study area spans two LRRs (Southern Alaska and Interior
Alaska) and three MLRAs (the Cook Inlet Mountains subregion in Southern Alaska, and the
Interior Alaska Mountains and Copper River Basin subregions in Interior Alaska; USDA-NRCS
2004). The Cook Inlet Mountains subregion encompasses the vast majority of both the Chulitna
and Gold Creek corridors. The easternmost extent of the Watana Reservoir extends into the
Copper River Basin subregion, while the remainder of the study area (the Denali Corridor, the
easternmost portions of the Chulitna and Gold Creek corridors, and the majority of the Watana
Dam site and Watana Reservoir) is located within the Interior Alaska Mountains subregion.
The Cook Inlet Mountains subregion includes portions of the Talkeetna, Kenai, and Chugach
mountains that drain into the Cook Inlet Lowlands MLRA and Cook Inlet, as well as portions of
the Alaska and Aleutian ranges (USDA-NRCS 2004). Portions of Denali National Park and
Preserve, Lake Clark National Park and Preserve, Kenai National Wildlife Refuge, and Chugach
National Forest are located within the Cook Inlet Mountains subregion. Rugged mountains,
deeply incised with narrow to broad, high-gradient valleys dominate the terrain in this subregion.
The climate is characterized by short summers with moderate to cold winters, with an average
frost-free period of 60–80 days. During the 2013 field surveys, 15 transects were sampled in the
Cook Inlet Mountains subregion, within the Chulitna and Gold Creek corridors. The wetlands
along those transects were dominated by saturated shrub types, intermixed with wetter emergent
wetlands, lakes, and ponds.
The Copper River Basin subregion includes portions of the Talkeetna, Chugach, and Wrangell
Mountains, and the Copper River Plateau (USDA-NRCS 2004). Glenallen is the largest
community within the Copper River Basin MLRA, and portions of the Wrangell-St. Elias
National Park and Preserve are located within this subregion. Undulating plains and rolling hills
dominate the terrain, with lakes and interconnecting wetlands in shallow basins. Most of this
subregion drains into the Copper River. The subarctic continental climate of this subregion is
characterized by brief, warm summers and long, cold winters, with an average frost-free period
of 35–90 days. The Copper River Basin MLRA is located within the discontinuous permafrost
zone, and near-surface permafrost is common in fine-textured sediments on plains, stream
terraces, and gentle slopes. Two survey transects were sampled in the Copper River Basin
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 15 February 2014 Draft
subregion in 2013; those transects were dominated by saturated shrub wetlands with scattered
occurrences of seasonally flooded/saturated emergent wetland types.
The Interior Alaska Mountains subregion includes the high mountain slopes and glaciated hills
and plains in the Alaska Range and in the Talkeetna, Chugach, and Wrangell mountains, the
northern portions of the Aleutian Range that drain into the upper Tanana and Kuskokwim rivers,
and the Copper River Plateau (USDA-NRCS 2004). This subregion is primarily undeveloped
and includes portions of Denali National Park and Preserve, Wrangell St-Elias National Park and
Preserve, and Tetlin National Wildlife Refuge. High rugged mountains, low rounded hills, and
extended footslopes along the base of mountains dominate the terrain, with narrow to broad
high-gradient valleys dissecting the mountains. This subregion drains to the Tanana River,
Kuskokwim River, Copper River Basin, the Cook Inlet Lowlands, and Cook Inlet. The subarctic
continental climate of this subregion is characterized by brief, warm summers and long, cold
winters, with an average frost-free period of 50–80 days. The Interior Alaska Mountains MLRA
is located within the discontinuous permafrost zone, with near-surface permafrost generally
restricted to fine-textured sediments on stream terraces and swales on hills and footslopes. The
majority (60) of the 77 survey transects sampled in 2013 were in the Interior Alaska Mountains
subregion; these transects were located within the Denali Corridor, in the study area just to the
north of the Watana Dam site, and in the study area surrounding the proposed Watana Reservoir.
The north-south and east-west trending portions of the Denali Corridor exhibit different aspects
of the Interior Alaska Mountains subregion: high-gradient valleys in the mountains and extended
footslopes, respectively. The north-south trending portion of the Denali Corridor is dominated by
subalpine physiography and dwarf to low shrubs typical of the broad, high-gradient valleys in
this subregion. In contrast, the east-west trending portion of the Denali Corridor is dominated by
a mix of upland and lowland physiography, with forested and low-shrub vegetation classes
typical of extended footslopes in this subregion. In 2013, saturated HGM slope shrub wetlands
were the most frequently sampled wetland types in all portions of the Denali Corridor, although
seasonally flooded/saturated emergent wetlands were frequently sampled in the north-south
trending portion of the corridor. Several forested wetland types were sampled at lower elevations
within the Interior Alaska Mountains subregion.
The wetland types sampled in the three MLRAs in the study area in 2013 should not be
interpreted as the expected distribution of classes in the final wetlands map. In particular, land-
access restrictions precluded sampling at lower elevations in most of the Gold Creek Corridor, in
much of the study area surrounding the Watana Dam site, and in the western portion of the
Watana Reservoir (Figure 3-1). Although few PFO4B wetlands were sampled in these areas in
2013, extensive lower elevation forests are visible in the aerial imagery for these areas.
Similarly, alpine physiography dominates the north-south trending portion of the Denali Corridor
in the aerial imagery, but the field survey efforts were focused on the more difficult-to-
distinguish subalpine saturated shrub wetland types.
6.1.2. Waters
The Susitna River is classified as a Traditionally Navigable Water (TNW) from Cook Inlet
upstream to the mouth of Portage Creek (ADNR 2012). The Nenana River, located in the
northern portion of the study area in the Denali Corridor (Figure 3-1), is classified as potentially
navigable. Within the study area, both rivers are large, upper perennial (R3UBH) riverine
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 16 February 2014 Draft
systems, characterized by year-round, high-gradient, and high-velocity flows of turbid waters full
of glacial silt. Neither river is tidally influenced within the study area. As expected for high-
velocity river systems, substrates are dominated by coarse rock fragments (cobbles and
boulders). Within the upper portions of these rivers that occur in the study area, the drainages are
relatively channelized and there is little floodplain development. Some seasonally flooded gravel
bars and islands in the channels of these rivers have been classified as wetland communities;
these areas are characterized by plant species that can grow in both wetland and upland
hydrologic regimes (R3USC and PSS1C). These communities have surface water (flooding) for
brief periods during the growing season, but the groundwater table is usually well below the
surface. An example of the wetlands mapping prepared for an upper perennial river system
(Nenana River) is presented in Figure 6.1-1.
Additional upper perennial waters in the study area include named and unnamed clear-water
tributaries of the Susitna and Nenana rivers. These waters are typically 3–6 m (10–20 ft) wide at
bankfull, with gravel- to boulder-dominated substrates; cover is provided by overhanging
riparian vegetation, and undercut banks and large woody debris are common. Dissolved oxygen
in the water at the time of sampling (July and August) was usually at or close to saturation.
Lower perennial rivers (R2UBH) are low-gradient rivers and streams with low velocity flows,
typically with sandy or silty substrates and well-developed floodplains. Due to the mountainous
terrain in the study area, these waters are less common than upper perennial rivers.
Intermittent waters (R4SBC) occur regularly in the study area and may be under-represented in
the mapping of water bodies because they are often too small to detect on aerial photography.
Surface water is only present in the spring or during summer flood events. These small,
intermittent tributaries typically originate at seeps or springs on hillsides, and alternate between
surface flow and subsurface flow in less steep terrain downslope.
Freshwater ponds (PUBH) are very common in the study area and occur in a variety of terrain
types. Ponds typically are characterized by shallow water and, following Cowardin et al. (1979),
can be up to 20 acres in area. They may be part of a larger lowland wetland complex or isolated
features within landscape depressions. Freshwater lakes (L1UBH) are lacustrine water bodies
greater than 20 acres in size (see Figure 6.1-2 and Appendix A). Lakes in the study area occur in
groups, notably near the south base of Deadman Mountain and within the Fog Lakes area.
6.1.3. Wetlands
As described above, saturated broadleaf deciduous shrub-scrub (PSS1B) was the most commonly
sampled NWI wetland type within the study area. Saturated, sloping, shrub wetlands are
probably the most common type in the study area, and the PSS1B code also includes the highest
number of AVC Level IV vegetation types (Viereck et al. 1992). Level IV types within the
PSS1B code include needleleaf woodlands with shrub dominated understories, both low and tall
willow and alder communities, the full range of low dwarf birch-dominated communities, as well
as the dwarf willow wetland types in subalpine and alpine tundra. Due to the wide diversity of
plant communities within this wetland type, it is likely to be a component of a number of
different wetland functional classes on the final wetlands map for the study area. PSS1B
wetlands are primarily HGM slope types, but they also occur as saturated fringes on the
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 17 February 2014 Draft
perimeters of larger, wetter, wetland complexes (as mapped in Figure 6.1-1), or as shrub types
occupying steep discharge slopes on upland or subalpine hillside (as described in Section 6.2,
Wetland Functional Assessment, below).
In addition to the common PSS1B wetland type, there were a number of other shrub-dominated
wetlands that have either seasonally flooded or seasonally flooded/saturated hydrologic regimes.
The most commonly sampled types in this category were seasonally flooded/saturated broadleaf
deciduous shrub-scrub (PSS1E, PSS1/EM1E) and seasonally flooded deciduous shrub-scrub
(PSS1C, PSS1/EM1C). The seasonally flooded types most commonly occur on well-drained
riverine interfluvial surfaces (e.g., gravel river bars) while seasonally flooded saturated types
often occupy the edges of low-lying wetland complexes or discharge slopes on middle or lower
mountain slopes. Where these wetlands occurred on wetter discharge slopes, surface water was
often present throughout, in depressions and in small channelized features.
The next most commonly sampled wetland types in the study area were the seasonally
flooded/saturated persistent emergent (PEM1E) and semi-permanently flooded persistent
emergent (PEM1F) types. These wetter, herbaceous wetlands do not cover large portions of the
study area, but they are common wetland types throughout. Seasonally flooded saturated
persistent emergent meadows were commonly found in low-lying troughs on flat plateaus above
the Susitna River (see Figure 6.1-1 and Appendix A). These are slope wetlands dominated by
wetland-obligate plants such as Carex aquatilis, Eriophorum russeolum, Trichophorum
cespitosum, or T. alpinum. Surface water was observed at all the PEM1E types sampled, and
many had indicators of a strongly reducing environment, such as a hydrogen sulfide odor or iron
deposits (flocculated iron and a biogenic sheen on standing water). PEM1E communities
included flooded, beaver-altered meadows; reticulated fens; or abandoned river oxbows. Semi-
permanently flooded persistent emergent marshes (PEM1F) are less common than PEM1E
wetlands, and are usually found immediately adjacent to open water bodies (see Figure 6.1-2 and
Appendix A). PEM1F wetlands often have low plant diversity; many are nearly pure stands of
tall, coarse, wetland-obligated sedges.
Six wetland-determination plots were located in saturated needleleaf forest wetlands (PFO4B).
All sampled PFO4B wetlands were open canopy or woodland black spruce forests, with
understories frequently dominated by Vaccinium uliginosum, V. vitis-idaea, and Equisetum
species. These forested wetlands occurred most often in toeslope areas.
Overall, the field data indicate a diversity of both wetland and upland types in the study area; 56
percent (505) of the 895 wetland-determination plots sampled in 2012 and 2013 were classified
as wetlands and 44 percent (390) were classified as non-wetlands. Over half the field points in
alpine, subalpine, and upland physiographic areas in the study area were classified as non-
wetland. Vegetation structure in non-wetland areas ranges from mature forests to moist
herbaceous and dry dwarf-shrub types. Field plots in subalpine non-wetland areas were nearly
evenly divided among dwarf shrub scrub, low birch-ericaceous, and tall alder and/or willow
scrub types . Field plots in non-wetland areas in riverine, upland, and lowland physiographic
areas were a mix of white spruce woodlands, open canopy white spruce-paper birch forests, low
birch-ericaceous scrub, and tall alder and/or tall willow scrub types.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 18 February 2014 Draft
6.2. Wetland Functional Assessment
The preliminary wetland functional assessment conducted for the 15 wetland field plots on two
example transects resulted in FCI values that represent the differences in function among various
HGM wetland classes (Table 5.3-1). For example, groundwater recharge does not occur or is
negligible in slope wetlands and hence the Modification of Groundwater Recharge function was
evaluated only for the riverine wetland plot (T139-06). Similarly, Modification for Groundwater
Discharge was highest for the riverine wetland plot due to its perennial outlet; high-permeability,
sub-surface geologic deposits; well-developed microrelief; and thick organic deposits. The
saturated shrub and forested slope wetlands had the lowest FCI values for groundwater discharge
due to the absence of perennial outlets; low-permeability, sub-surface geologic deposits; and a
predominantly acidic water regime. Seasonally flooded/saturated and semi-permanently flooded
slope wetlands had moderate FCI values for groundwater discharge. Their perennial outlets and
thick organic deposits indicate that groundwater discharge is likely happening, while their low-
permeability, sub-surface geologic deposits likely limit the amount of groundwater/surface water
interaction.
The lack of a channelized outlet is a direct indicator of function (FCI = 1) for the Storm and
Floodwater Storage function in HGM Slope wetlands. The majority of saturated slope, scrub and
forest wetlands have no inlet and no outlet, and thus were assessed as fully functioning (FCI = 1)
for Storm and Floodwater Storage (Table 5.3-1). A modification to this direct indicator of
function is being considered to better represent the range of functional differences in HGM slope
wetlands without an outlet, as indicated by the footnoted FCI values in Table 5.3-1. This
potential change, if made, will be implemented and discussed in the USR. The remaining
wetland types evaluated had moderate FCI scores for Storm and Floodwater Storage. While
seasonally flooded and semi-permanently flooded wetlands have surface roughness and
microrelief characteristics suitable for storage of storm and floodwater, their limited additional
storage capacity for water minimizes water retention.
The lack of a channelized outlet is a direct indicator of the absence (FCI = 0) of the Modification
of Stream Flow function. Consequently, saturated scrub and forested wetlands with no
channelized features were considered not to provide this function (Table 5.3-1). Forest or scrub
wetlands located within or adjacent to sloping wetland complexes with channelized features
received highest FCI rankings for the Modification of Stream Flow function and open water
bodies received the lowest rankings.
The Modification of Water Quality function was rated high for all of the 15 plots evaluated
(Table 5.3-1). HGM slope, forest, and scrub wetlands score the highest for this function (FCI =
0.87–1.0; Table 5.3-1) due to their high surface roughness, lack of channelized features, and
thick organic soils. The remaining seasonally flooded or semi-permanently flooded wetlands also
scored highly (FCI ≥ 0.8) for this function due to the presence of thick organic layers, which are
capable of slowing down water movement and storing particulates and dissolved elements. The
model for the Modification of Water Quality function may be restructured in the next year of
study to better reflect the pristine condition of the wetlands in the study area, as opposed to
wetlands in more developed areas. The Magee model was developed for wetlands in proximity to
human developments with significant pollutant sources, which is not the case in the study area.
The primary indicator of water quality function in the Magee model, evidence of sedimentation,
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 19 February 2014 Draft
may be modified to better represent the natural, rather than anthropogenic, sources of sediment in
the largely undisturbed study area. This change, if made, will be discussed in the USR.
The Export of Detritus function is primarily controlled by outlet class in HGM slope wetlands.
The lack of an outlet is a direct indicator of no function (FCI = 0) because regardless of the
quantity or quality of organic material produced, it is unlikely to be flushed on a regular basis
from wetlands with no outlet. Conversely, a vegetated wetland with a perennial outlet will rank
moderate to high for Export of Detritus (Table 5.3-1). Riverine wetlands typically have high
potential for export of detritus, especially in very dynamic systems with frequent, seasonal,
overbank flooding. The single riverine plot considered in this preliminary functional assessment,
however, was rated moderate (FCI = 0.67) for Export of Detritus due to the presence organic
soils (indicative of organic retention, rather than export) and a moderate (vs. high) vegetation
density.
As defined by Magee (1998), the Contribution to Abundance and Diversity of Wetland
Vegetation function makes no distinctions between upland and wetland-adapted species, nor
does it incorporate rare or sensitive species. The derivation of FCI values for this function
depends on three variables: plant diversity, vegetation density, and proximity and connections to
other wetlands. Of the types evaluated in this preliminary functional assessment, the highest
ranking wetlands were the saturated HGM slope wetlands that had at least two vegetation strata,
such as a shrub-birch canopy and a dwarf ericaceous and herbaceous understory. One potential
alteration to the model for the Contribution to Abundance and Diversity of Wetland Vegetation
function would be to incorporate results from the Rare Plant Study being conducted for the
Project (see ISR Study 11.8). This alteration could be another spatially explicit modification to
the functional assessment methods to link rare plant population locations with wetland functional
classes. This approach would be a Project-specific modification to allow the identification of
those wetland functional classes most likely to support rare plant species, and to identify the
specific locations of those wetland functional classes in the study area known to support rare
plant populations. This change, if made, will be implemented and discussed in the USR.
As with the Contribution to Abundance and Diversity of Wetland Vegetation function, the
Contribution to Abundance and Diversity of Wetland Fauna function makes no distinction
between upland or wetland-adapted species, disregards fish, and considers habitat suitability only
from a general perspective. The model for the Contribution to Abundance and Diversity of
Wetland Fauna function is focused on degree of human disturbance, plant community structure,
wetland size, and interspersion of wetland types. In this preliminary functional assessment,
human disturbance was considered to be low throughout the study area, and for this initial model
run, interspersion of wetland types was artificially low because only individual plots were
assessed. As a result, the faunal diversity function was rated moderate for all evaluated plots
(Table 5.3-1). As discussed above in Section 4.3, Wetland Functional Assessment, this function
will be modified in the next year of study by incorporating Project-specific fish and wildlife data
to generate spatially-explicit assessments of the use of wetlands in the study area by fish and
wildlife.
In general, the preliminary run of the Magee portion of the wetland functional assessment model
prepared for this report returned expected FCI values for the HGM wetland types considered,
although several alterations to the models for various functions, as noted above, are being
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 20 February 2014 Draft
considered to improve the accuracy and applicability of the FCI values to the study area. The
Magee functional assessment model allows for such flexibility (e.g., modification or removal of
variables), and as more HGM classes are added to the analysis and the wetland classification and
mapping of the study area advances, it is expected that more modifications to the model will be
made to better represent the functions of the large, undisturbed wetland systems in the study
area.
As described in RSP Section 11.7.7, data inputs from the following interrelated studies will be
used to provide spatially-explicit information on wetland function in the study area: Fish
Distribution and Abundance Studies (Studies 9.5 and 9.6), plus the Characterization of Aquatic
Habitats in the Susitna River with Potential to be Affected by the Susitna-Watana Project (Study
9.9) as indicated above in Section 4.3; all Wildlife Resource Studies (Studies 10.5–10.18); the
Subsistence Baseline Documentation Study (Study 14.5); and Recreation Resources Study
(Study 12.5). The Program Lead for the fish studies reports that the clear-water tributaries
upstream of the Project dam site were surveyed for fish occurrence and fish habitats in 2012 and
2013, and the tributaries along the possible Susitna-Watana transmission line/road corridors are
planned to be sampled in the next year of study. The Program Lead for the wildlife studies
indicates that the wildlife surveys for the Project are on track and that data have been collected
on the occurrence of large mammals (Studies 10.5 through 10.8), furbearers (Studies 10.9
through 10.11), bats (Study 10.13), birds (Studies 10.15 through 10.17), and amphibians (Study
10.18). Data on the occurrence of small mammals (Study 10.12) will be collated from the
scientific literature in the next year of study. The study lead for the Recreation Resources Study
(Study 12.5) indicates that general use areas for hunting/trapping and fishing in the Project area
have been defined, and similar information on generalized areas for subsistence use is available
from the subsistence resources study. The data from each of these studies will be available to
incorporate in the wetland functional assessment work in the next year of study, and no changes
in these interrelated studies will affect the use of data noted above in the wetlands functional
assessment.
7. COMPLETING THE STUDY
[As explained in the cover letter to this draft ISR, AEA’s plan for completing this study will be
included in the final ISR filed with FERC on June 3, 2014.]
8. LITERATURE CITED
ABR (ABR, Inc.—Environmental Research & Services). 2013. Wetland mapping study in the
Upper and Middle Susitna Basin. Prepared for the Alaska Energy Authority, Anchorage,
AK, by ABR, Inc., Fairbanks and Anchorage, AK. 22 pp. Available on-line at
http://www.susitna-watanahydro.org/type/documents/. Accessed October 2013.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 21 February 2014 Draft
ADEC (Alaska Department of Environmental Conservation) and USACE (U.S. Army Corps of
Engineers). 1999. Operational draft guidebook for reference based assessment of the
functions of precipitation-driven wetlands on discontinuous permafrost in Interior
Alaska. Technical Report WRP-DE-__. Alaska Department of Environmental
Conservation, Anchorage, AK, and U.S. Army Corps of Engineers, Engineer Waterways
Experiment Station, Vicksburg, MS.
ADNR (Alaska Department of Natural Resources). 2012. Navigable Waters Web Map. Available
on-line at http://www.navmaps.alaska.gov/navwatersmap/ Accessed November 2013.
AEA (Alaska Energy Authority). 2012. Revised Study Plan: Susitna-Watana Hydroelectric
Project FERC Project No. 14241. December 2012. Prepared for the Federal Energy
Regulatory Commission by the Alaska Energy Authority, Anchorage, AK. Available on-
line at http://www.susitna-watanahydro.org/study-plan. Accessed October 2013.
Brinson, M.M. 1993. A hydrogeomorphic classification for wetlands. Technical Report WRP–
DE–4, U.S. Army Corps of Engineers, Army Engineer Waterways Experiment Station,
Vicksburg, MS.
Brown, J., O. J. Ferrians, Jr., J. A. Heginbottom, and E. S. Melnikov. 1998 (revised February
2001). Circum-arctic map of permafrost and ground ice conditions. National Snow and
Ice Data Center, Boulder, CO. Digital media.
Cowardin, L. M., V. Carter, F. C. Golet, and E. T. LaRoe. 1979. Classification of wetlands and
deepwater habitats of the United States. Northern Prairie Publication 0421. U.S.
Department of the Interior, Fish and Wildlife Service, Washington, DC. 131 pp.
Dahl, T. E., J. Dick, J. Swords, and B. O. Wilen. 2009. Data collection requirements and
procedures for mapping wetland, deepwater and related habitats of the United States.
Division of Habitat and Resource Conservation, National Standards and Support Team,
Madison, WI. 85 pp. Available on-line
athttp://www.fws.gov/wetlands/documents/gNSDI/DataCollectionRequirementsProcedur
es.pdf. Accessed September 2013.
Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual. Technical
Report Y-87-1. Vicksburg, MS: U.S. Army Corps of Engineers, Engineer Waterways
Experiment Station. Available on-line at
http://el.erdc.usace.army.mil/wetlands/pdfs/wlman87.pdf. Accessed September 2013.
Gracz, M. 2011. Cook Inlet Lowland Wetlands. Available on-line at
http://cookinletwetlands.info/. Accessed September 2013.
Hall, J. V., J. E. Powell, S. Carrack, T. Rockwell, G. Hollands, T. Walter, and J. White. 2003.
Wetland functional assessment guidebook, operational draft guidebook for assessing the
functions of slope/flat wetland complexes in the Cook Inlet Basin Ecoregion, Alaska,
using the HGM approach. Technical Report WRP-DE-__. Alaska Department of
Environmental Conservation, Anchorage, AK, and U.S. Army Corps of Engineers,
Engineer Waterways Experiment Station, Vicksburg, MS. 160 pp.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 22 February 2014 Draft
Jorgenson, M. T., J. E. Roth, S. F. Schlentner, E. R. Pullman, and M. Macander. 2003. An
ecological land survey for Fort Richardson, Alaska. Technical Report ERDC/CRREL
TR-03-19. U.S. Army Corps of Engineers, Engineer Research and Development Center,
Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire. 100 pp.
Lichvar R. W. 2013. The National Wetland Plant List: 2013 wetland ratings. Phytoneuron 2013-
49: 1–241.
Magee, D. W. 1998. A rapid procedure for assessing wetland functional capacity based on
hydrogeomorphic (HGM) classification. Bedford, NH.
Munsell Soil Color Charts. 2009. Revised edition. Gretag Macbeth, New Windsor, NY.
National Wetlands Inventory Center. 1995. Photointerpretation conventions for the National
Wetlands Inventory. U.S. Fish and Wildlife Service, St. Petersburg, FL. 60 pp.
NCDC (National Climatic Data Center). 2013. U.S. Department of Commerce. Climate data
available on-line at http://www.ncdc.noaa.gov/cdo-web. Accessed November 2013.
Smith, R. D., A. Ammann, C. Bartoldus, and M. M. Brinson. 1995. An approach for assessing
wetland functions using hydrogeomorphic classification, reference wetlands, and
functional indices. Technical Report WRP–DE–9, U.S. Army Corps of Engineers,
Engineer Waterways Experiment Station, Vicksburg, MS.
USACE (U.S. Army Corps of Engineers). 2007. Regional supplement to the corps of Engineers
Wetland Delineation Manual: Alaska Region (Version 2.0). Technical Report ERDC/EL
TR-07-24. September 2007. Wetlands Regulatory Assistance Program. U.S. Army Corps
of Engineers, Engineer Research and Development Center, Vicksburg, MS. 130 pp.
USDA (United States Department of Agriculture) NRCS (Natural Resources Conservation
Service). 2004. Land Resource Regions and Major Land Resource Areas of Alaska. 91
pp. Available on-line at: http://www.ak.nrcs.usda.gov/technical/lrr.html. Accessed
November 2013.
USDA (United States Department of Agriculture) NRCS (Natural Resources Conservation
Service). 2010. Field Indicators of Hydric Soils in the United States, Version 7.0. L. M.
Vasilas, G. W. Hurt, and C. V. Noble (eds.). United States Department of Agriculture and
Natural Resources Conservation Service, in cooperation with the National Technical
Committee for Hydric Soils.
Viereck, L. A., C. T. Dyrness, A. R. Batten, and K. J. Wenzlick. 1992. The Alaska vegetation
classification. General Technical Report PNW-GTR-286. U.S. Department of
Agriculture, Forest Service, Pacific Northwest Research Station, Portland, OR. 278 pp.
Washburn, A. L. 1973. Periglacial Processes and Environments. Edward Arnold, London,
England.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 23 February 2014 Draft
9. TABLES
Table 5-1. Mean Monthly Air Temperature and Cumulative Precipitation for Two Weather Stations Within the Wetland
Mapping Study Area, Susitna-Watana Hydroelectric Project, Alaska, 2013.1
Mean Air Temperature (°F) Total Precipitation (Inches)
30-yr Mean Monthly Means Anomaly 30-yr Mean Monthly Totals Anomaly
Station Month 2012 2013 2012 2013 2012 2013 2012 2013
Cantwell 4E April 27.2 30.7 11.6 3.5 -15.6 0.71 1.14 0.00 0.43 -0.71
May 41.4 40.3 35.7 -1.1 -5.7 0.77 0.59 0.02 -0.18 -0.75
June 51.3 51.3 56.8 0.0 5.5 1.87 3.22 0.07 1.35 -1.80
July 55.2 52.2 56.6 -3.0 1.4 2.53 1.29 1.00 -1.24 -1.53
August 50.6 50.4 53.2 -0.2 2.6 3.24 1.55 0.00 -1.69 -3.24
Chulitna
River April2 30.6 36.0 26.0 5.4 -4.6 1.38 0.53 0.47 -0.85 -0.91
May2 42.8 41.7 37.2 -1.1 -5.6 1.03 0.59 2.76 -0.44 1.73
June 52.8 52.0 57.7 -0.8 4.9 1.65 3.74 0.69 2.09 -0.96
July 55.5 52.3 57.9 -3.2 2.4 3.92 2.30 1.86 -1.62 -2.06
August2 51.8 51.3 56.1 -0.5 4.3 5.83 4.71 0.74 -1.12 -5.09
Notes:
1 Source: NCDC 2013.
2 Data from these months are incomplete: April 2013, n = 20 days; May 2013, n = 20 days; August 2013, n = 17
days.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 24 February 2014 Draft
Table 5.1-1. Wetlands and Waters Sampled in the Field in 2012 and 2013 and Mapped, as of Mid-November 2013, in the
Wetland Mapping Study Area, Susitna-Watana Hydroelectric Project.1
NWI Code2 Code Description3 No. Wetland Determination Plots No. Map-verification Plots
n (2012)4 n (2013) n (2012)4 n (2013)
Waters
R2UBH Lower perennial river 9 5
R2USC Seasonally flooded lower perennial shore 1 1
R3UBH Upper perennial river 20 8 23
R3USC Seasonally flooded upper perennial shore 4
R4SBC Seasonally flooded intermittent streambed 2 4 3
L1UBH Permanently flooded lake 3
PUBH Permanently flooded pond 28 1 7
PUBHb Permanently flooded pond (beaver modified) 1
Wetlands
PUSC Seasonally flooded unconsolidated shore 3 4
PUSCb Seasonally flooded unconsolidated shore (beaver
modified) 1
PMLE Seasonally flooded/saturated moss lichen 1
PEM1H Permanently flooded persistent emergent 4 4 3
PEM1F Semi-permanently flooded persistent emergent 11 21
PEM1Fb Semi-permanently flooded persistent emergent (beaver
modified) 1 4 12
PEM1E Seasonally flooded/saturated persistent emergent 30 51 4 31
PEM2E Seasonally flooded/saturated Non-persistent emergent 1 1 1
PEM1C Seasonally flooded non-persistent emergent 2
PEM1B Saturated persistent emergent 6 9 1 2
PEM1Bb Saturated persistent emergent (beaver modified) 2
PEM1/SS1F Semi-permanently flooded persistent emergent/broadleaf
deciduous shrub-scrub 1 1
PEM1/SS1E Seasonally flooded/saturated persistent
emergent/broadleaf deciduous shrub-scrub 4 4 3
PEM1/SS1C Seasonally flooded persistent emergent/broadleaf
deciduous shrub-scrub 1
PEM1/SS1B Saturated persistent emergent/broadleaf deciduous
shrub-scrub 3 8 2
PSS1/EM1E Seasonally flooded/saturated broadleaf deciduous shrub-
scrub/persistent emergent 5 7 1
PSS1/EM1C Seasonally flooded broadleaf deciduous shrub-
scrub/persistent emergent 1
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 25 February 2014 Draft
NWI Code2 Code Description3 No. Wetland Determination Plots No. Map-verification Plots
PSS1/EM1B Saturated broadleaf deciduous shrub-scrub/persistent
emergent 6 12 3
PSS3/EM1B Saturated needleleaf deciduous shrub-scrub/persistent
emergent 1 1
PSS1E Seasonally flooded/saturated broadleaf deciduous shrub-
scrub 8 15 3 6
PSS1C Seasonally flooded broadleaf deciduous shrub-scrub 4 16 4 2
PSS1B Saturated broadleaf deciduous shrub-scrub 23 116 11 51
PSS1/3B Saturated broadleaf deciduous/evergreen shrub-scrub 1 4
PSS1/4B Saturated broadleaf deciduous/needleleaf evergreen
shrub-scrub 13 3
PSS3B Saturated broadleaf evergreen shrub-scrub 1 1
PSS3/1B Saturated broadleaf evergreen/deciduous shrub-scrub 1 5
PSS3/4B Saturated broadleaf/needleleaf evergreen shrub-scrub 1 1
PSS4E Seasonally flooded/saturated needleleaf evergreen shrub-
scrub 1 1
PSS4B Saturated needleleaf evergreen shrub-scrub 3 6 1
PSS4/1B Saturated needleleaf evergreen/broadleaf deciduous
shrub-scrub 2
PSS4/3B Saturated needleleaf/broadleaf evergreen shrub-scrub 3
PFO4B Saturated needleleaf evergreen forest 6 5
U Upland 150 240 44 129
Total 276 619 85 295
Notes:
1 Shaded rows are sampled wetland classes that have not yet been mapped.
2 Following Cowardin et al. (1979).
3 Following Dahl et al. (2009).
4 Based on additional data review, the 2012 map classes were revised from those previously reported in ABR
(2013).
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 26 February 2014 Draft
Table 5.3-1. Functional Capacity Index (FCI) Values, Following Magee (1998), for Wetland-determination Plots on Two
Transects (T139 and T182) in the Wetland Mapping Study Area, Susitna-Hydroelectric Project Area, 2013.
Field Plots Grouped into
Preliminary Wetland Functional
Classes
HGM
Class NWI Type1 Modification of Groundwater Discharge Modification of Groundwater Recharge 2 Storm and Flood Water Storage Modification of Stream Flow Modification of Water Quality Export of Detritus Abundance & Diversity of Vegetation Abundance & Diversity of Fauna Permanently Flooded Ponds
SW13_T139_07 Slope PUBH 0.53 N/A 0.33 0.22 1 0.53 0.47 0.57
SW13_T182_01 Slope PUBH 0.33 N/A 0.38 0.22 0.67 0.53 0.47 0.53
Saturated Deciduous Shrub Scrub
SW13_T139_13 Slope PSS1B 0.47 N/A 13 0 0.93 0 0.6 0.67
SW13_T182_03 Slope PSS1B 0.33 N/A 13 0 0.8 0 0.73 0.7
SW13_T182_05 Slope PSS1/4B 0.33 N/A 13 0 0.8 0 0.73 0.7
SW13_T182_06 Slope PSS1B 0.47 N/A 1 3 0 0.93 0 0.73 0.7
Saturated Evergreen Forest
SW13_T139_12 Slope PFO4B 0.47 N/A 13 0 1 0 0.47 0.63
Saturated Evergreen Shrub Scrub
SW13_T139_03 Slope PSS4/3B 0.33 N/A 13 0 1 0 0.73 0.57
SW13_T139_11 Slope PSS4/3B 0.67 N/A 0.62 0.67 0.87 0.8 0.73 0.67
Seasonally Flooded Deciduous Shrub Scrub
SW13_T139_06 Riverine PSS1C 0.87 0.5 0.46 0.67 1 0.67 0.6 0.73
Seasonally Flooded/Saturated Deciduous Shrub Scrub
SW13_T139_09 Slope PSS1E 0.73 N/A 0.48 0.67 0.8 0.67 0.73 0.67
Seasonally Flooded/Saturated Emergent Meadow
SW13_T139_01 Slope PEM1E 0.53 N/A 0.38 0.44 0.8 0.6 0.6 0.6
SW13_T139_14 Slope PEM1E 0.67 N/A 0.43 0.67 0.8 0.53 0.47 0.7
Seasonally Flooded/Saturated Emergent/Shrub Scrub
SW13_T139_05 Slope PEM1E 0.53 N/A 0.38 0.44 0.8 0.6 0.6 0.63
SW13_T182_02 Slope PEM1/SS1E 0.47 N/A 0.48 0.44 0.8 0.4 0.47 0.67
Semi-Permanently Flooded Emergent Meadow
SW13_T139_04 Slope PEM1F 0.53 N/A 0.38 0.44 0.8 0.6 0.6 0.63
Notes:
1 Following Cowardin et al. (1979) and Dahl et al. (2009).
2 Groundwater recharge function not assessed for HGM slope wetlands.
3 Potential modifications to model pending, to better reflect variable wetland functional capacity (see text).
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 27 February 2014 Draft
10. FIGURES
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 28 February 2014 Draft
Figure 3-1. Study Area and Ground-reference Plots Sampled in 2013 for the Wetland Mapping Study, Susitna-Watana Hydroelectric Study Area.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 29 February 2014 Draft
Figure 6.1-1. Preliminary Map of Riverine Waters and Riparian Palustrine Wetlands in the Denali Corridor,
Susitna-Watana Hydroelectric Project, 2013.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 30 February 2014 Draft
Figure 6.1-2. Preliminary Map of Lacustrine Waters and Associated Palustrine Waters and Wetlands in an
Area West of the Proposed Project Dam Site, Susitna-Watana Hydroelectric Project, 2013.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 31 February 2014 Draft
Figure 6.1-1. Preliminary Map of HGM Slope (Fen) Wetlands in the Gold Creek Corridor, Susitna-Watana
Hydroelectric Project, 2013.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 February 2014 Draft
APPENDIX A: PHOTOGRAPHS OF REPRESENTATIVE WETLAND
TYPES SAMPLED IN THE VEGETATION AND WILDLIFE HABITAT
MAPPING STUDY AREA, SUSITNA-WATANA HYDROELECTRIC
PROJECT, 2013.
INITIAL STUDY REPORT WETLAND MAPPING STUDY IN THE UPPER AND MIDDLE SUSITNA BASIN (11.7)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Appendix A – Page 1 February 2014 Draft
Permanently Flooded Lake (L1UBH) Semi-Permanently Flooded Persistent Emergent
(PEM1Fb) Beaver Modified
Seasonally Flooded/Saturated Persistent Emergent
(PEM1E)
Seasonally Flooded/Saturated Broadleaf Deciduous
Shrub Scrub (PSS1E)
Saturated Broadleaf Deciduous Shrub-Scrub (PSS1B) Saturated Broadleaf Deciduous Shrub-Scrub (PSS1B)