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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

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d, cstr

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3/15/

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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

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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