The dams can create significant pools, saturating and weakening the roadway structure. If not removed, the water behind the dam can cover the highway. If the roadway fill becomes over saturated, a fill failure can necessitate closure of the highway.
Beavers often build dams in waterways containing populations of federally-protected fish.
In these circumstances the dams can only be removed during seasonal in-water work windows and only after proper coordination with regulatory agencies and with approved permits in place. Typically, beaver dam building does not coincide with the in-water work window. Beaver dam removal is also expensive. Potential prevention methods need to address many different parameters, such as water velocity, bedload movement, large woody material movement, and water volume. Numerous devices and methods have been developed to prevent beavers from blocking culverts while still maintaining fish passage and adequate stream flow.