Assessing the Effects of Beaver Dam Analogues on Channel Morphology using High-Resolution Imagery from Unoccupied Aerial Vehicles (UAVs)

The loss of beaver and their dams in the western US due to trapping and habitat loss has reduced former beaver meadows and wetlands to single thread, incised stream channels. In response to this degradation, landowners have begun to implement beaver-inspired stream restoration projects, such as constructed beaver dam analogues (BDAs). BDAs are intended to restore incised streams by increasing sediment deposition in the channel, promoting ponding and groundwater storage, and improving riparian vegetation health.

In collaboration with The Nature Conservancy of Wyoming (TNC), we have assessed the effects of BDA stream restoration projects in Red Canyon Creek, a meandering second-order stream that runs through a TNC-owned livestock ranch. TNC installed a sequence of 5 BDAs along a 500 m reach of Red Canyon Creek in spring and summer of 2018. We completed unoccupied aerial vehicle (UAV) surveys of the BDA restoration site in 2017 (prior to BDA installation), 2018 (immediately following BDA installation), and in 2019 (one year following BDA installation). Using visible light UAV imagery and Structure from Motion methods, we generated annual digital elevation models (DEMs) of the experimental BDA reach with centimeter-scale accuracy. We used these high-resolution DEMs to quantify sediment accumulation upstream of the BDAs and changes in bank sedimentation and erosion due to BDA installation. We compare these changes measured in the DEMs to field measurements of 50 erosion pins installed in summer 2018. Little change occurred during the year prior to BDA installation, followed by extensive shifts in channel morphology after one year of BDA presence in the creek. Our findings show that BDAs significantly alter channel morphology, contributing to our understanding of the impacts of these low-tech stream restoration structures on degraded streams.