The Rainbow Lake restoration and reconfiguration project is funded through a State of WA capital budget grant to WDFW for the design and restoration of the lake. The lake was created for the purpose of mitigating lost fisheries as part of the Lower Snake Compensation Program. The lake was created as a reservoir on the floodplain in the late 50's to provide fishing opportunity as wild steelhead numbers declined. By the 2000's the lake was severely silted in and require high level of maintenance, while providing minimal wildlife recreation benefit. The reservoir also provides a water source for the Tucannon River Fish Hatchery, where trout for stocking the put and take fisheries in the lakes. The Rainbow Lake Project aimed to improve the quality (depth) of the lake and minimize its impact on the Tucannon River floodplain. The habitat focus of the project removed ~0.18 miles of river levee to create 3.8 acres of river connected wetland. Construction was completed in the fall of 2018.

Work designed and implemented at Rainbow Lake is closely tied to the in-stream work funded through the BPA Habitat Programmatic for the Project Area 13 (PA-13) which is located within the active channel and floodplain from the Hatchery Dam at RM 40.0 to the hatchery access road bridge at RM 39.2. The lake project will provide a better fishing opportunity to sportsman while allowing more habitat benefit to ESA protected salmonids within the Tucannon River. In the Spring of 2020, WDFW will initiate restoration action in the river reach to address the conditions listed below.

6.1.1.1 Channel Characterization

The channel is characterized as a single-thread, plane-bed channel with forced pool-riffle and local rapid sections. The channel is typically straight, wide, and contains little complexity in much of the project area. Large levees confine the channel throughout the project area. These levees are located along the right bank from approximately RM 39.95 to 39.8, at RM 39.6, and from RM 39.5 to 39.2. The levees are heavily armored with large angular boulders. The hatchery dam at the upstream end of the project area controls the channel grade. No significant side channels or off-channel areas were observed at the time of field reconnaissance. The quality and availability of instream habitat is restricted by the lack of channel and hydraulic complexity. The straight and confined channel results in hydraulic conditions that create high velocities and high transport capacity. These conditions do not support the retention of LWD and bedload, and, therefore, lack hydraulic complexity. A few downed logs and one log jam provide pools and cover, but overall very few adequate pools for adult holding are available. The lack of side channels (except some apparent high-flow channels) limits the quantity of habitat for rearing juveniles.

6.1.1.2 Floodplain Characterization
Floodplain connectivity in this reach is affected by the presence of infrastructure, and little low-lying floodplain is present in the project area. However, there is low floodplain present near RM 39.8 and 39.3 that is disconnected by infrastructure. Although there is not a high quantity of disconnected floodplain, likely because of local channel incision, the levees are armored and prevent channel migration and the development of gravel bars and low-lying emergent floodplain. Rainbow Lake, the public camping areas, and the access road to these areas are located atop a terrace and not within the low-lying floodplain. The riparian zone is generally in moderately good health, except for along the levees, which are typically populated with invasive understory species. The levees are typically sparsely vegetated with shrubs and covered in thistle and other weedy plants that provide little overhang. The disconnected low-lying area in the east floodplain near RM 3