Author Results: C. Westbrook


Incorporating beaver dams in a physically-based hydrological model

A current challenge in ecohydrology is the incorporation of beaver dams into hydrological models. Select works have attempted to solve this problem using routing approaches, Manning coefficient variations, pond dynamics, or fully-distributed hydraulic models; however, all these approaches assume that all beaver dams are homogeneous structures and react in the same way to rainfall events. Recent findings highlight the importance of including the functional heterogeneity of beaver dams, especially the water path past the dam (dam flow state). To overcome the challenge of accounting for different dam flow states interrupting downstream water transmission in different ways, we developed BEAVERPY, a flow state-based Python package that can be coupled with the platform Cold Regions Hydrological Model (CRHM) to represent both streamflow modulation by ponds and dams, while also simulating infiltration and evapotranspiration. We used the broad-crested weir equation for the overflow dams, the Darcy equation for the seep flow dams, and the v-notch weir equation for the gapflow dams, verifying each case with synthetic experiments. To calibrate and validate the model, we instrumented the ponds and streams in a peatland fen in the Canadian Rocky Mountains in Alberta with level sensors and ‘DamCams’ (trail cameras) to capture flow type. Then, we used LIDAR DEM data and high-resolution imagery to delineate the hydrological response units. Each pond is represented as an HRU, which can interact with soil and routing modules. Finally, we conducted a scenario-testing experiment to understand the sensitivity of different beaver dam flow states for several storms. The results indicate the importance of including flow state dynamics for the beaver dam representations, and highlight the importance of integrating animal-ecological aspects into the streamflow modelling. This research has implications for understanding the use of  beaver as a nature-based solution for flood mitigation and river restoration.

Relative Effectiveness of Four Different Guards In Preventing Beaver Cutting of Urban Trees

Beavers are expanding into cities as they recolonize their historic range. While they increase the ecological functioning of urban green areas, human-beaver conflicts occur. Public support to deal with conflicts has shifted from population to forage control. Tree guards are becoming popular with management personnel in North America and Europe to reduce damage to valuable trees. The problem is that this management technique has not been studied. We inventoried the tree guard types in use in natural and manicured river parks in the City of Saskatoon, Canada, determined their adherence to an installation protocol by measuring guard dimensions, and assessed the relative effectiveness of guards in protecting trees from beaver cutting. The inventory revealed that four types of tree guards are in use, ranging from light gauge chicken wire to heavy gauge chain link fencing. Overall, 11% of the trees with guards that we inventoried were cut by beavers, but variation among guard types was observed. Less than 10% of trees with type i and ii guards were beaver cut whereas 17% of trees with types iii and iv guards were beaver cut. Fewer trees were cut when there was adherence to installation protocol, regardless of guard type. Cut trees with guard types i, iii and iv experienced both minor and major damage whereas cut trees with guard type ii experienced only minor damage. The study results have implications for developing effectiveness and implementation monitoring plans for tree guards as part of an overall beaver management plan.

Distribution of Canadian Rocky Mountain Wetlands Impacted by Beaver

We studied the distribution of beaver-impacted mineral wetlands and peatlands in a 7,912 km2 area of the Canadian Rocky Mountains. Using aerial photography and an existing wetland database, we inventoried 529 wetlands at elevations of 1,215 to 2,194 m; peat soils were found at 69 % of the 81 field verified wetlands.

Beaver Dams and Overbank Floods Influence Groundwater–Surface Water Interactions of a Rocky Mountain Riparian Area

This study provides empirical evidence that beaver can influence hydrologic processes during the peak flow and low?flow periods on some streams, suggesting that beaver can create and maintain hydrologic regimes suitable for the formation and persistence of wetlands.