DESCRIPTION
The 3-D project occupies river miles 24-25 of the Entiat River, it is a fish habitat enhancement project for listed salmonids in the Upper Columbia region. The project was originally scheduled to be implemented in 2011 as part of the Integrated Monitored Watershed (IMW) approach; however due to unseasonably high flows in 2011 the project was bumped back until 2012 implementation and more favorable flow conditions.
The project itself consists of seven bank-based engineered log structures (ELSs), one pond connector channel, one backwater alcove, one non-flow through side-channel and one flow-through side-channel. The property consists of private, Chelan Douglas Land Trust and USFS parcels.
This fish habitat enhancement project recreates habitat that is below historical and potential conditions. A total of 7 bank-based engineered log structures (ELSs) were constructed in areas that would naturally accumulate wood in addition to areas in this reach lacking in-channel cover complexity and diversity. Vertical piles were driven into each structure to provide additional stability. Cable was used to anchor structures in place and to fasten logs to vertical snags.
In addition to large wood placement, there are five locations where backwater or off-channel rearing habitats for juvenile salmonids was created. These types of habitats are located in existing natural backwater areas that can be enhanced by widening and lengthening to increase the total usable area during low flow stage and discharge. Imported wood was used at each site for cover and complexity habitat.
There are two types of off-channel design that were constructed based on how they function with the river. The first type does not have water running through it, but behaves like a cutoff oxbow channel and fluctuates in wetland and habitat area based on the stage of the Initiate River. In this type of channel, the excavated segments are free draining to prevent fish stranding as water levels drop in the summer. The backwater channel extend its length and area as river stage rises. Large wood was imported and vertical snags were buried for cover habitat within those enhanced backwater areas.
A second type of off-channel habitat that was created was habitat with surface water running through constructed off-channel habitats. At this location more complex pools were formed. The pools are maintained by surface water, reducing the risk of stranding and mortality as Entiat River flows reduce in the summer.
An additional site at the downstream end of the reach takes advantage of Brennegan Creek. At this site, an old Entiat River channel was excavated to increase total habitat area, allowing Brennegan Creek which flows from a huge wetland beaver complex, to feed water through it to the outlet and into the mainstem Entiat River. The intent/strategy of this work was to create habitat that fish can use now to help make up the habitat deficit that has occurred following human disturbance.
