Muskrats, in some situations, can be excluded or prevented from digging into farm pond dams through stone rip-rapping of the dam. A more comprehensive approach would be the installation of heavy-gauge wire mesh (1" x 1" or smaller) down to a minimum depth of 6 feet. Serious damage, if anticipated, can often be prevented by constructing dams to the following specifications:
? the inside face of the dam should be built at a slope of 3 to 1;
? the outer face of the dam should be build at a slope of 2 to 1, with a top width not less than 8 feet (2.4 m), preferably 10 to 12 feet (3 to 3.6 m).
The normal water level in the pond should be at least 3 feet (91 cm) below the top of the dam, and the spillway should be low and wide enough so that heavy rainfalls will not increase the level of the water for a significant length of time. These specifications are often referred to as overbuilding, but they will generally prevent serious damage from burrowing muskrats.
Additional methods include exclusion fencing in situations where muskrats may be leaving a pond or lake to cut valuable garden plants or crops, together with trapping, and cultural practices such as removal of all aquatic plant species and palatable plant species growing in the vicinity of the pond.
Resources: (online)
Muskrats
