Beaver Dam Analog Suitability

Analyzing elevation data to determine suitable sites to implement Beaver Dam Analog projects (BDAs) in order to restore incised streams.

Streams go through phases of development dependent on their surrounding conditions. These phases can be considered more or less healthy for the ecosystem that depends on the stream. Stages where there is a high degree of incision and high water velocity are less suitable for stream life than stages with lower velocities and meandering channels. The ideal stage for restoration is Stage 0, where the stream bed is the same elevation as the floodplain. The cost of restoring streams to Stage 0, can be very high, if it is possible at all. Beyond the amount of material needed to raise the stream bed, the associated disturbances require expensive mitigation and drawn out permitting.

Beaver Dam Analogs (BDA) are a low cost, low disturbance method for restoring incised creeks to stage 0 conditions. traditionally material would be added to the incised stream bed to raise it to the level of the floodplain. A BDA is just that: a structure of mud and organic materials gathered from the stream banks, built to block the flow of water. BDAs lower the water velocity and act as sieve that accumulate sediment over time. This sediment settles and raises the stream bed. The materials harvested from the bank allow for heterogeneous erosion, analogous to beaver channels one observes in a natural beaver pond. As the habitat improves over time, beavers can be reintroduced, taking on the long term maintenance costs. 

BDAs cannot be installed just anywhere. They must be in a location with steep stream banks in an otherwise flat floodplain. To locate suitable sites for BDAs, I created a suitable site index on properties McKenzie River Trust owns or holds easements on. The index favors a high degree of slope calculated from a 10 meter DEM (steep banks) with a low degree of slope from a 30 meter DEM (flat floodplain).