Ecosystem Diagnosis and Treatment (EDT) model for the Stillaguamish River Basin

1. Ecosystem Diagnosis and Treatment (EDT) model for the Stillaguamish River Basin Michael D. Purser, Senior Habitat Specialist Snohomish County Public Works Surface Water Management Everett, WA

2. Overview • EDT is a habitat rating model. • Data for 43 attributes are collected and the attributes are calculated or estimated for all reaches that are the habitat of Chinook salmon. • The attributes include direct factors (e.g., large woody material, pool area, water quality, etc.), and indirect factors such as hydrology.

3. Model Outputs Model outputs include: • a baseline report comparing current and historic Chinook salmon population performance • an analysis of the relative importance of preservation and restoration actions in each subbasin, and • a reach-scale analysis of the influence of specific actions on specific life history stages.

4. Attributes • Default attribute values were created in an initial effort that was commissioned by the Tulalip Tribes and the WDFW (2002). • New data were used to update attribute values such as physical habitat, water quality data, and riparian condition. • TAG members reviewed the original dataset, the proposed changes, and the documentation supporting the revisions.

5. Fish Populations • Spawning reaches and timing and harvest patterns are defined for both North Fork and South Fork Chinook salmon populations. • The model predicts viable salmonid population parameters (VSP’s): • life history diversity, • productivity, • capacity (maximum number of recruits supportable), and • equilibrium abundance for returning spawners and outmigrating smolts for both populations.

6. Baseline and Diagnostic Results The initial results from the model include: • an assessment of Current and Template conditions on the VSP parameters (Baseline Report); • an analysis of benefits to each population of restoration and protection by subbasin; and • a reach-level analysis of the effect of attributes on the productivity of each life stage known to use the reach (Diagnostic Reports).

7. Actions and Scenarios • EDT can model scenarios comprised of specific actions to see the effect on adult and juvenile Chinook salmon. • The model was also used to confirm that the scenarios created would have benefit to the focal species. • Actions modeled in EDT include: • riparian restoration, • floodplain connectivity/side-channel restoration, • reduction of sediment, and • restoration of large woody debris (in concert other activities as well as stand-alone projects).

8. Results

10. Diagnostic Reports – fall run (SF) • Protection priorities: • Jim Creek • Lower Pilchuck Creek • Restoration priorities: • Lower Stillaguamish River, • Lower South Fork, and • Jim Creek

12. Diagnostic Reports – summer/fall run (NF) Protection priorities • French-Segelsen • Middle North Fork Stillaguamish Restoration priorities • Lower North Fork, • Middle North Fork • French-Segelsen

14. Key Findings • Reconnecting estuarine marsh had the largest response of any action. • Riparian planting • The long-term (25 years or more) benefits of riparian planting increased productivity more than any other scenario. • Even in 10 years, planting yielded a significant increase in productivity and capacity through improvements in water quality.

15. Key Findings (cont’d) • Improve in-channel structure through placement of LWD • Wood has the most benefit where it changes the distribution of habitat features (i.e., increase primary and backwater pools which are limiting throughout the system). • Important short-term measure because riparian plantings that may occur today will not contribute significant LWD for 50 years or more. • 15-20% increase in productivity, capacity and abundance.

16. Key Findings (cont’d) • Reconnecting off-channel habitat • Significant for both populations assuming a large percentage of reconnected habitat becomes backwater pool with good food and cover. The effect of reconnection alone was relatively small because the area of off-channel habitat is small relative to the total reach area. • The effect was greater in the South Fork.