Lower Boise Creek Project, King County - DNRP

Project Background: The Lower Boise Channel Restoration Project is located on 15 acres situated along the left bank of the White River. In the 1930’s the lower 500 feet of Boise Creek was relocated between the Northern Pacific RR and SR-410. This created a channelized and over-steepened stream with no floodplain or pools and limited spawning and rearing habitat.

Goals: The goal of the restoration project was to relocate the lower reach and mouth of Boise Creek into a new channel configuration and alignment to restore the natural stream geomorphic structure, functions, and habitat-forming processes, while also protecting Tacoma Water’s Pipeline. The design approach was to establish an alluvial fan floodplain with large wood to provide roughness, allowing the creek to scour pools, form riffles, build terraces, and actively migrate, providing habitat for fish and wildlife, and an expanded riparian buffer. The project targeted improvements in spawning, rearing, and refuge habitat for juvenile salmonids including summer and fall Chinook, pink, coho, and chum salmon, as well as native cutthroat and steelhead trout.

Objectives
• Relocate approximately 500 lineal feet of the existing channel and increase channel length to approximately 600 lineal feet.
• Create approximately 2 acres of alluvial fan floodplain habitats.
• Establish a minimum 150-wide (average) buffer of native vegetation along each side of the channel.
• Place 150 pieces of large woody debris (LWD), including 6 cubic meters of key large woody debris (KLWD), to create in-stream habitat. • Design the channel and floodplain to provide fish passage at low flows and to minimize velocities and scour during the bankfull flow.

B-IBI sampling was conducted by King County DNRP annually after project installation between 2011 and 2013 at up to three locations: control reach, old channel, and new channel. The sample collection targeted riffle habitat from 8 square feet using a Surber sampler and 500 micron mesh net. Taxonomic identification was to medium resolution with chironomids (midges) identified to subfamily and most other organisms identified to lowest practical level (typically genus or species). Pre project data are available in 2009 and 2010 from King County Roads site E2168 and E2168D/S under King County Roads.

Contact: Laura Hartema, Laura.Hartema@kingcounty.gov, 206-477-4708