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

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. Overview. EDT is a habitat rating model.

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

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  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

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

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

  11. 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.

  12. 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.

  13. 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.

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