Urban Beaver Activity Management and Qualitative Risk Assessment Using GIS

Extreme weather events are expected to increase the burden on urban stormwater infrastructure as the climate continues to change. Beavers (castor canadensis) are well known for their engineering prowess and ability to rapidly naturalize degraded urban streams. This has a multitude of benefits including stormwater retention, groundwater recharge, ecological restoration, and erosion reductions; however, beavers and stormwater managers frequently clash through the clogging of stormwater outlets and the destruction of beaver dams. Beavers are routinely trapped, and their dams destroyed, only to have new beavers re-colonize the area in an endless, costly cycle. This project demonstrates a GIS-based method to predict where beaver activity may be an issue in a stormwater network using land cover to identify ideal beaver habitat at chokepoints in a stormwater network. Areas where roads cross streams in the Fletcher’s Creek watershed in Brampton, Ontario were ranked based on the amount of land cover nearby that could increase the likelihood of beaver habitation and associated blocking of sensitive stormwater infrastructure such as culverts at stream-street crossings. This ranking could theoretically allow stormwater managers to prioritize monitoring. If this method is tested and verified in the field it could prove useful for stormwater infrastructure planners by allowing them to invest in cost-effective beaver deterrents at key locations before a human-beaver conflict arises, potentially reducing costs for maintenance activities and allowing beavers to continue provide their natural stormwater management services.