The King County Department of Natural Resources and Parks is proposing to to develop a habitat restoration and flood reduction plan and associated design concept alternatives for Boise Creek between 284th Avenue SE and its confluence with the White River near Enumclaw, Washington (AKA Middle Boise). The goal of this effort is to develop design alternatives to a proof-of-concept level.

In 2010 King County performed a geomorphic assessment of Middle Boise Creek that included public outreach, conceptual design development, and a land availability assessment. A basic hydraulic analysis was performed of different design alternatives using a HEC-RAS model where the main flow of Boise Creek has left its banks during floods. As a result of this feasibility assessment process a willing property owner agreed to sell property for the design and construction of a projec that would improve agricultural productivity, reduce flooding, and improve fish habitat.

The proposed modelling work will build upon the previous work to construct a two-dimensional hydraulic model of the project site using the FLO-2D software program to identify the flooding characteristics with greater resolution. Conceptual design alternatives will be developed, tested with the hydraulic model, and modified in coordination with the County until a proof-of-concept design can be achieved.

The Assessment would deliver:
- A 2D Model for Middle Boise Creek between 284th Avenue SE (RM 4) and the White River (RM 0).
- Habitat Restoration Site Identification (at least 10 future habitat restoration projects will be identified alon Boise Creek).

Boise Creek is used by several anadromous fish species including ESA-listed Chinook and steelhead, along with chum, pink, and coho salmon. White River spring Chinook, which spawn and rear in Boise Creek, are the only spring population in South Puget Sound and are also genetically the most distinctive stock in south and central Puget Sound. The spring Chinook run is only one of four populations of spring Chinook in Puget Sound. Boise Creek is the major accessible Chinook, steelhead, and coho spawning area just prior to the PSE Diversion Dam, thereby elevating Boise Creek's importance for maintaining salmon populations in the White/Puyallup River watershed.

In 2004, King County completed the Boise Creek Rapid Rural Reconnaissance Report to gain a better understanding of the drainage systems, streams, and habitat issues in the Boise Creek sub-basin. Boise Creek water quality is degraded as documented in the 201) Puyallup River Watershed Water Quality Improvement Report (WDOE. In 2012, King County completed the Middle Boise Creek Feasibility Analysis which assessed this impacts to this waterbody via historic drainage projects, channelization, excavating sediment, and agricultural activities like grazing. The proposed 2D model will complete the necessary analysis of Boise Creek and facilitate future restoration projects between the Enumclaw Golf Course and the mouth of Boise Creek.

Boise Creek is in tremendous need of restoration, since it's channel is entrenched, streambanks steepened, and there's very little riparian vegetation and instream wood. Minimal channel sinuosity exists for most of the lower four miles. Stream temperatures in Boise Creek regularly exceed Washington State standards for salmon spawning and incubation, and for juvenile rearing. Based on recorded high water temperatures, Boise