Installing beaver dam analogues (BDAs) in degraded streams is an increasingly common restoration technique in western North America. In some locations, such as Trail Creek near Gunnison, Colorado, the goal of these installations is to create wetland areas within the stream corridor. Using a reach-scale approach, we sampled aquatic invertebrate community composition, water velocity, and substrate grain size in three 500m reaches: a beaver pond reach (with breached dams), a BDA-treated reach, and an untreated reach. Our objective was to assess whether the BDA-treated reach exhibited physical and biological characteristics consistent with wetland habitats. We found that the BDA reach supported a more homogenous aquatic invertebrate community composition compared to the other reaches. The BDA reach had lower flow and deeper depths than the beaver reach and the untreated reach, and the untreated reach had larger median grain size than the other two reaches.
The next year, the beaver ponds had been abandoned and were no longer intact; however, the BDA structures had been colonized and augmented by beavers. Taking a habitat-scale approach, we then compared aquatic invertebrate community composition, temperature, substrate size, pond depth, and pond area between untreated stream pools, BDA ponds, and beaver-augmented BDA ponds. Community composition differed among habitat types. The BDA ponds had significantly lower daily high temperatures compared to stream pools, and the beaver-augmented ponds had significantly lower daily highs than the BDA ponds. Beaver-augmentation also resulted in lengthening the dams and deepening the ponds. Beaver-augmented BDA ponds were rounder in shape than BDA ponds, which often were just deeper versions of the existing stream channel shape. Our results have implications for how BDA installation spacing should be designed, such as by potentially leaving room between some structures for more riffle-like flow to avoid loss of habitat diversity. Overall, these results support that BDAs change habitat towards wetland status, but beavers enhance wetland outcomes.