Phase II - Beaver Dam Analog Construction in Hoopa Reservation Streams

Beaver dam analogs were constructed in the upper reaches of Supply Creek, between the mouth of Campbell Creek and the SR96 and in Soctish Creek upstream of Pine Creek Road. In total 12 beaver dam analogs were installed. Additionally repairs were made to two BDA in supply creek from an earlier year that had been taken out via scour and a large tree in supply creek, and one was extended to river right to enhance the channel evolution that was occurring at this location. The height and placement of these structures can affect more than one meso habitat. If placed at the base of a split channel then more than one pool can be created as was seen in Supply Creek. Alternatively if the structure increases the water surface elevation it can in crease depth beyond a riffle crest and change 2 runs into pools, as the initial result in Campbell Creek. Once in place sediment dropped out of suspension upstream at this location and an alternating bar sequence was created making a pool on river left and another just upstream on river right.

SONCC in the lower Trinity River are identified in the Recover Plan as being at high risk of extinction. Restoration of tributary habitat for both natal and non-natal SONCC is therefore of great importance. Ponds and backwater habitats that form upstream of beaver dams were identified in the SONCC recovery plan as high-quality summer and winter rearing habitat for Coho salmon, and so this project is expected to suport increases in survival and growth of Coho as well as the other native anadromous salmonids. Beavers are expected to occupy some or all of the BDAs, and when doing so will sustain and enhance the features.

Therefore, long-lasting ecological benefits are anticipated. Besides the direct habitat benefit to Coho, beaver dams and BDAs can enhance aquatic and riparian functions. Some of these functions are: sequestering of fine sediment until high flows can transport them to floodplains or downstream reaches, recharge of groundwater in adjacent floodplains, increasing hyporheic flows, raising of water tables that support native riparian vegetation, and helping to sustain flows during drought periods. These functions in turn benefit Coho, other aquatic species and terrestrial species that use the riparian corridor.