Environmental factors influencing beaver dam locations

Beavers are known for their ability to build dams that change the environment. They also occupy territories where they do not construct dams. The goal of this study was to determine which environmental factors influence beaver dam construction and to examine the upstream water level increase caused by the dams. We compared factors collected at 15 beaver territories with dams (32 dams) and 13 territories without dams (i.e., control) in the gently undulating and human-dominated landscape of Middle Belgium in 2013. River width, river depth, distance from woody vegetation, stream velocity, and bank height differed significantly between territories with and without dams. Water depth was the most important parameter to correctly classify territories as either dam territory or control territory (with 97% accuracy). When beavers were present and water depth in summer was <68 cm, the probability of dam building was high; if water depth was >68 cm, dam building was unlikely. Dams caused an increase in the upstream water level of on average 47 +/- 21 cm. On average the water level could rise only an additional 25 +/- 30 cm upstream of the dam before bank overtopping would occur. These results provide a simple tool for planners to assess the probability of floodplain inundation by beaver dam building, as part of multifunctional riverine landscape management. (c) 2018 The Wildlife Society.