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Final Report for the Habitat Strategic Initiative
Floodplain Condition Assessment and Vital Sign Refinement
(Formerly titled: Floodplain Recovery Target Refinement)
ESA, Washington Department of Ecology, and Puget Sound
Partnership
NTA 2016-0401
WDFW Contract 17-08308
March 25, 2019
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Title: Floodplain Condition Assessment and Vital Sign Refinement (formerly titled Floodplain
Recovery Target Refinement) Final Project Report
Authors: Ilon Logan, Colin Hume, Jennifer Burke
Organization: ESA, Washington Department of Ecology, and Puget Sound Partnership
Year: 2019
Keywords: Floodplains, Vital Sign indicator, Common Indicator
Series Name: Puget Sound National Estuary Program
Grant Program: Habitat Strategic Initiative
Granting Agencies: Washington Dept. of Fish and Wildlife, Washington Dept. of Natural Resources
EPA Grant Number: PC-01J22301
Sub-recipient Grant No (Agency + No): 17-08308
Grant name: 66.123 PugetSound Action Agenda: Technical Investigations and Implementation
Assistance/Environmental Protection Agency
Near Term Action Number 2016-0401
Reference Number in other databases (e.g. PRISM XXXX): none
Summary:
In 2017 a project was initiated to refine the baseline condition assessment used to establish the
Floodplains Vital Sign indicator target for Puget Sound. A regional advisory committee and three pilot
watershed technical committees were convened over the course of 10 months to recommend criteria,
decision-rules, and methods by which to establish a historic-geomorphic floodplain extent and baseline
conditions using spatial data. Major products of the effort include robust documentation of the process
and GIS methods, as well as a spatial database of existing floodplain extent and conditions available for
viewing and download. Recommendations for project-level reporting which would contribute to making
progress on the Target were made and will be proposed to grant programs. Recommendations for an
improved Floodplain indicator target were also made and will be considered in future updates to the
Vital Sign program established by the Puget Sound Partnership.
Suggested citation:
ESA, Washington Department of Ecology, and Puget Sound Partnership. 2019. Floodplain Condition
Assessment and Vital Sign Refinement. Tacoma, Washington.
https://pspwa.box.com/s/f7b67a765ni5i5hjnf4moks44e9ol36x. March 31, 2019.
https://pspwa.box.com/s/f7b67a765ni5i5hjnf4moks44e9ol36x
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Table of Contents
Project Goals and Objectives ............................................................................................................... 4
Methods ................................................................................................................................................. 4
Results ................................................................................................................................................... 5
Project Outcomes .............................................................................................................................. 5
Success of Achieving Performance Measures................................................................................. 9
Conclusions ......................................................................................................................................... 10
Lessons Learned ............................................................................................................................. 10
Recommendations for Future Work .............................................................................................. 10
List of Tables
Table 1 – Summary Results for Regional Mapping
Table 2 – Summary Results for Floodplain Extent by Watershed
Table 3 – Summary Results for Conditions Assessment by Watershed
Table 4 – Summary of Project Performance Measures
Attachments
Attachment A – Map Exhibits
This project has been funded wholly or in part by the United States Environmental Protection Agency under assistance agreement
PC-01J22301 through the Washington Department of Fish and Wildlife. The contents of this document do not necessarily reflect the
views and policies of the Environmental Protection Agency or the Washington Department of Fish and Wildlife, nor does mention
of trade names or commercial products constitute endorsement or recommendation for use.
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Project Goals and Objectives
The Floodplain Condition Assessment and Vital Sign Refinement project was initiated by the
Washington State Department of Ecology (Ecology) and Puget Sound Partnership (Partnership,
PSP) to establish the foundation to assess, monitor, and report information regarding the
Partnership’s Floodplain Implementation Strategy, Vital Sign, and Common Indicator
programs. The objective of the project was to develop consensus for a regional floodplain
“footprint” and condition assessment of the floodplain across all (17) major rivers1 in the Puget
Sound to help monitor progress in protecting and restoring floodplain conditions. By engaging
technical teams in three different pilot watersheds (Dungeness, Green-Duwamish,
Stillaguamish), and a Regional Advisory Committee to establish and vet methods, this project
developed a regionally-accepted floodplain footprint and assessment of condition, in addition
to criteria for activities to include in reporting recovery progress. This project is one step
towards the goal of successfully quantifying and communicating floodplain investments and
restoration across Puget Sound.
Methods
The Partnership contracted Environmental Science Associates (ESA) and Carol MacIlroy
Consulting to provide management, facilitation, and technical assistance in carrying out the
project. The project had the following elements:
Convening a regional advisory committee for 7 meetings over the course of ten months.
Refining the criteria and methods for mapping the floodplain extent and assessing
floodplain condition building on an existing interim dataset developed in support of the
Floodplain Implementation Strategy in 2015.
Conducting pilot assessments of floodplains in three Puget Sound watersheds
(Green/Duwamish, Stillaguamish, and Dungeness watersheds) using the refined criteria
and methods.
Recommending improved criteria and methods, accounting for local knowledge, data,
and perspective while cognizant of regional needs.
Refining and solidifying methods for assessing and reporting floodplain location and
condition Sound-wide in the remaining non-pilot watersheds.
Recommending criteria and performance metrics for tracking project-level change in
floodplain condition as they can contribute to the Vital Sign tracking over time.
This project was guided by the Advisory Committee who established the criteria and methods
for integrating existing geospatial datasets of floodplain boundaries and land cover/land use to
delineate floodplain extent and assess the function within the delineated floodplain areas. In
1 This project and the PSP’s Vital Sign are focused on floodplains in the 17 major rivers (16 rivers with estuarine deltas and the Cedar River):
Big Quilcene River, Cedar River, Deschutes River, Dosewallips River, Duckabush River, Dungeness River, Elwha River, Green/Duwamish
River, Hamma Hamma River, Nisqually River, Nooksack River, Puyallup River, Samish River, Skagit River, Skokomish River, Snohomish
River, Stillaguamish River.
http://wa-rco.maps.arcgis.com/apps/View/index.html?appid=729159a20952401ca1dad205ff14651d
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addition to the Advisory Committee, three pilot watersheds were selected for this project to
support the refinement of methods and data sources based on guidance from local experts in
each watershed. The pilot watersheds were the Green-Duwamish, Stillaguamish and
Dungeness Rivers. The project produced a set of GIS map layers that characterize floodplain
extent and baseline conditions across 17 major rivers in Puget Sound and a consistent set of
performance metrics and tracking rules that could be used by Puget Sound grant programs.
The geospatial methods used to develop the floodplain dataset are presented in a Geospatial
Methodology Report.
Results
PROJECT OUTCOMES
The project produced two types of outcomes: analytical conclusions of the Advisory Committee
in the form of key decisions and recommendations and a floodplains geodatabase with a
companion document of GIS methods. The key decisions and recommendations of the
Advisory Committee addressed all the components of the Floodplain Condition Assessment
and Vital Sign Refinement project, including:
Floodplain Extent
Conditions Assessment
Floodplain Tiers/Categories
Project Tracking for assessing Vital Sign Indicator progress
Decision Rules for Incorporating Local Data
The Floodplains Condition Assessment and Vital Sign Refinement report created for the project
describes all of the key decisions and recommendations made by the Advisory Committee and
provides context where applicable. Additionally, recommendations for ways to improve the
Floodplain Indicator Target in the future are outlined in that document (deliverable 3.1).
The GIS analysts on the contractor team synthesized and operationalized the criteria and
decision rules for mapping the floodplain extent and conditions assessment and applied it to
the 17 major Puget Sound watersheds using the GIS methods described in the Geospatial
Methodology Report. The results of the final outputs for the pilot and regional assessments
were aggregated into an ESRI file geodatabase that included multiple feature datasets (one for
each pilot watershed and one all watersheds combined). The database was developed to be
consistent with the Partnership’s Programmatic GIS QAPP (PSP, 2014).
The Regional Approach to the floodplain extent resulted in 438,935 acres of mapped floodplain
(Attachment A, Map Exhibit 1). Table 1 summarizes the conditions assessment by floodplain
categories and the proportion of each category within the regional extent. Map Exhibit 2
provides a visual example of the conditions assessment for a portion of the Snohomish River.
https://pspwa.box.com/s/f7b67a765ni5i5hjnf4moks44e9ol36xhttps://pspwa.box.com/s/z1ace5h62z1wayqlarurpanqpcuql6b0https://pspwa.box.com/s/z1ace5h62z1wayqlarurpanqpcuql6b0
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Due to the large extent of project mapping and the level of detail produced by the conditions
assessment, it is unfeasible to depict the regional floodplain conditions on a single map.
Table 1 – Summary Results for Regional Mapping
Floodplain Mapping Component Area (acres) Proportion
of Area
Extent Floodplain Extent 438,935 100.0%
Conditions
Assessment
Floodplain Categories
a - Connected Natural Land Cover 156,363 35.6%
b.1 - Connected Agriculture 32,746 7.5%
b.2 - Connected Open Space 26,854 6.1%
b.3 - Connected Built 9,527 2.2%
c - Disconnected Natural Land Cover 50,424 11.5%
d.1 - Disconnected Agriculture 83,557 19.0%
d.2 - Disconnected Open Space 34,711 7.9%
d.3 - Disconnected Built 44,752 10.2%
Total Functional 156,363 35.6%
Total Degraded 282,572 64.4%
Of the 17 major Puget Sound watersheds, over half (55%) of the mapped floodplain extent is within three
watersheds: Nooksack River, Skagit River, and Snohomish/Snoqualmie/Skykomish Rivers (Map Exhibit
3). Table 2 summarizes the floodplain extent by watershed.
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Table 2 – Summary Results for Floodplain Extent by Watershed
Table 3 summarizes the amount of functional floodplain (Category A) and degraded floodplain
(Categories B, C, and D) for each watershed. The 17 watersheds vary widely in size so the proportion of
total floodplain extent is also shown.
Extent
(acres)
Big Quilcene River 766 0%
Cedar/ Sammamish/ Lake Washington 13,196 3%
Deschutes River 5,892 1%
Dosewallips River 1,217 0%
Duckabush River 574 0%
Dungeness River 7,777 2%
Duwamish River 35,432 8%
Elwha River 3,111 1%
Hamma Hamma River 932 0%
Nisqually River 24,182 6%
Nooksack River 52,578 12%
Puyallup River 40,574 9%
Samish River 20,254 5%
Skagit River 109,509 25%
Skokomish River 9,459 2%
Snohomish/ Snoqualmie/ Skykomish River 80,008 18%
Stillaguamish River 33,474 8%
Grand Total 438,935 100%
Watershed Proportion of Total Extent
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Table 3 – Summary Results for Conditions Assessment by Watershed
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SUCCESS OF ACHIEVING PERFORMANCE MEASURES
The following table lists the performance measures established at the outset of the grant and
provides commentary on outcomes (Table 4).
Table 4 – Summary of Project Performance Measures
Project Performance Measures Outcome
Team of regional experts establish
consensus criteria for floodplain
extent and function/degradation
metrics
Regional Advisory Committee successfully convened 7
times providing critical feedback and direction to the
project.
Consensus criteria for floodplain
function/degradation applied to
floodplain footprint to determine
baseline status and current
conditions for three watersheds
Criteria establish and vetted through the Advisory
Committee meetings and process.
Consensus criteria used in pilot
watersheds (3-4) to determine a
set of decision-rules to establish
baseline floodplain footprint for
all 17 major river floodplains
Criteria vetted in 3 pilot watersheds and baseline status for
all 14 major floodplains established. Additionally, pilot
watersheds requested a “subset” of floodplain area which is
more frequently flooded and prioritized for restoration. This
was implemented with local data and provided to the pilot
watersheds for their own recovery planning purposes.
Decision-rules validated with
local floodplain community and
refined
Decision-rules validated through Advisory Committee
process and pilot watershed process. Post-project outreach
will determine how broadly these are accepted across the
floodplain community.
Floodplain grant programs have
consensus criteria available to
inform project selection and track
performance
Initial recommendations for project tracking using
consensus criteria have been documented. Floodplains by
Design management team and PSEMP committee have been
presented initial performance tracking concepts and will
(among other grant programs) continue to be engaged post-
project to achieve broad use of the information generated. It
was determined that the floodplain extent, not the condition
assessment, was most applicable for project selection.
Floodplain indicators evaluated,
revisions proposed to Science
Panel as necessary to consistently
track progress
Current restoration indicator has been evaluated using
refined baseline floodplain condition results. Final report
provides options for refining the indicator in the future but
does not propose a new target. This will be pursued post-
project and incorporated into the Partnership’s re-envisions
of the indicators for 2020.
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Project Performance Measures Outcome
Quantified floodplain baseline
status and condition of function in
three watersheds for reporting
progress towards target
Baseline status for all 17 watersheds complete with a more
refined version in the 3 pilot watersheds which utilizes local
data integrated.
Conclusions
LESSONS LEARNED
This project sought to develop regional data and products that local and state resource
managers would view as reasonably accurate, well-developed, and useful to them. To
achieve success, a clear and transparent process was key along with responsiveness and
follow-through with individual committee members.
The three pilot watersheds (Green-Duwamish, Dungeness, and Stillaguamish) each
endorsed and understood the need for the regional target to be based in an assessment
of how much historic geomorphic floodplain was lost, including those areas
“permanently” disconnected due to flood management infrastructure. However, for the
project to benefit local recovery planning additional mapping of a “subset” of the
floodplain which is more frequently inundated is more valuable. The available data to
establish that subset of the floodplain differs in each watershed and so cannot be
established through a top-down regional process. Additional work across the remaining
14 watersheds, building off of the methods and process established in this project, will
provide a more refined regional tracking tool and add value to local recovery planning.
The importance of having explicit and well-articulated statements about the purpose
and appropriate application of a regionally-developed dataset cannot be overstated.
This project developed a dataset that was useful in informing regional targets and
policy, but is not to be used in making small (or site) scale decisions (such as funding or
project selection).
Engaging at the local level with the pilot technical teams successfully facilitated a
process to obtain, integrate, and vet the results of the local data with the local experts as
part of the regional process.
RECOMMENDATIONS FOR FUTURE WORK
Application of the approach and methodology to the other 14 watersheds (non-pilot
watersheds) is recommended for improving the suitability of the dataset for tracking progress
under the Floodplain Vital Sign and also for increasing the use of the dataset in local recovery
planning efforts. Additionally, the Partnership and Ecology will continue to engage the
recovery community to refine the Floodplain Vital Sign target using the recommendations
which resulted from this project as detailed in the Floodplains Condition Assessment and Vital
https://pspwa.box.com/s/f7b67a765ni5i5hjnf4moks44e9ol36x
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Signs Refinement report. The target should strike proper balance between being ambitious but
achievable and be based in the refined baseline established by this project. Lastly, additional
outreach efforts to grant programs are needed to “operationalize and institutionalize”
performance metric reporting that contributes and communicates progress towards the
Floodplains Vital Sign target.
https://pspwa.box.com/s/f7b67a765ni5i5hjnf4moks44e9ol36x
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Attachment A
Map Exhibits
HammaHamma River
DeschutesRiverNisquallyRiver
SkokomishRiverPuyallup River
Duwamish/GreenRiver
DuckabushRiverDosewallips River
Cedar River/ Sammamish River/ Lake Washington
BigQuilceneRiverSnohomish/SnoqualmieRiver/Skykomish
DungenessRiver
ElwhaRiver
StillaguamishRiverSkagit River
NooksackRiver
SamishRiver
Path: U
:\GIS\G
IS\Proje
cts\17x
xxx\D1
70337_
PSP_F
loodpl
ains\0
3_MXD
s_Proje
cts\Rep
ort\Ext
ent.mx
d, cstr
uthers
3/15/
2019
SOURCE: DigitalGlobe, 2016; ESA, 2019
Regional Baseline Floodplain Extent 0 20Miles
Puget Sound Partnership Floodplain Spatial Data Refinement for Monitoring ProjectMap Exhibit 1Results of Regional Approach to Floodplain Mapping
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Marysville
Everett
Lake Stevens
Snohomish
Mill Creek
Path: U:\GIS\G
IS\Projects\17xxxx\D170337_PSP_Floodplains\03_MXDs_Projects\Report\Conditions.m
xd, cstruthers 3/14/2019
SOURCE: DigitalGlobe, 2016; ESA, 2019
a - Con n ected Natural Lan d Coverb.1 - Con n ected Agricultureb.2 - Con n ected Open Spaceb.3 - Con n ected Builtc - Discon n ected Natural Lan d Coverd.1 - Discon n ected Agricultured.2 - Discon n ected Open Spaced.3 - Discon n ected Built 0 2
Miles
Puget Soun d Partn ership Floodplain Spatial Data Refin em en t for Mon itorin g ProjectMap Exhibit 2Exam ple of Results from Con dition s Assessm en t – Sn ohom ish River
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HammaHamma River
DeschutesRiverNisquallyRiver
SkokomishRiverPuyallup River
Duwamish/GreenRiver
DuckabushRiverDosewallips River
Cedar River/ Sammamish River/ Lake Washington
BigQuilceneRiverSnohomish/SnoqualmieRiver/Skykomish
DungenessRiver
ElwhaRiver
StillaguamishRiverSkagit River
NooksackRiver
SamishRiver
Path: U
:\GIS\G
IS\Proje
cts\17x
xxx\D1
70337_
PSP_F
loodpl
ains\0
3_MXD
s_Proje
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ort\Ext
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atersh
eds.mx
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2019
SOURCE: DigitalGlobe, 2016; ESA, 2019
Other Regional Baseline Floodplain ExtentsNooksack River Baseline Floodplain ExtentSkagit River Baseline Floodplain ExtentSnohomish/Snoqualmie River/Skykomish Baseline Floodplain Extent 0 20
Miles
Puget Sound Partnership Floodplain Spatial Data Refinement for Monitoring ProjectMap Exhibit 3Top 3 Watersheds Comprising Regional Floodplain Extent
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Floodplains_NEPFinalProgressReport_NTA2016-0401_AttachmentA.pdfExtent_Watersheds_v2Extent_v2DeltasConditions