Hydraulic Modeling of Beaver Dams and Evaluation of Their Impacts on Flood Events

• Main Authors: Michael Neumayer, Sonja Teschemacher, Sara Schloemer, Volker Zahner, Wolfgang Rieger
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Water
• Subjects: eurasian beaver; beaver territories; beaver dam cascades; inundation area; peak flow attenuation; hydraulic modeling; field survey; hydro_as-2d
• Online Access: https://www.mdpi.com/2073-4441/12/1/300

There is a general agreement on the impact of beaver dams regarding the increasing diversity of habitats and the improvement of the water quality, whereas the retention effect during flood events is still being discussed. In this study, we modeled 12 beaver dam cascade scenarios in two catchments for eight flood events with a two-dimensional (2D) hydrodynamic model. The implementation of the potential cascades in the model is based on the developed three-stage model for predicting location-dependent dam cascades in Bavaria. A Bavaria-wide questionnaire regarding dam occurrences and characteristics in combination with a detailed survey of 51 dams was used to set up a prediction scheme. It was observed that beaver dams are most likely built in rivers with riparian forest, with widths from 2 to 11 m and depths smaller than 1 m. The hydraulic model results showed larger inundation areas (>+300%) for the beaver dam scenarios. There is a noticeable peak attenuation and translation for elevated peak discharges (five times the annual mean discharge: up to ≤13.1% and 2.75 h), but no remarkable effect could be observed for flood events with return periods of more than 2 years. We conclude from the results that beaver dam cascades can have an impact on runoff characteristics, but do not lead to relevant peak reductions during flood events and therefore cannot be counted as flood mitigation measure.