Diversion Dam Culvert Protection
A Diversion Dam is constructed 10 to 15 feet upstream of the culvert inlet so when the beavers dam upon it the inlet is not obstructed. The goal is to create the beginnings of a beaver dam. It works best if it holds back a little water and creates a noisy waterfall that will attract the beaver’s attention. The beaver will then choose to build on top of your Diversion Dam rather than the culvert.
It can be made from any variety of materials, including fencing or rocks. Anything that will start the dam impoundment. Make it 1 foot higher than the water level to prevent the beavers from going over it to continue to dam the culvert.
If using fencing, both ends of the fence should terminate on high ground leaving an 18 inch gap between the culvert and the fence so large turtles and other wildlife can continue to use the culvert for passage. Interestingly, usually beavers will not go up on dry land and then back down into the culvert with damming materials, so the wildlife passage does not usually result in a dammed culvert. However, if beavers use the wildlife passage to dam inside the culvert, then the passage may need to be closed off for a season or two to break that behavior.
At low flow sites with plenty of large rocks, in lieu of a fence, a rock berm can be built across the stream to create the small impoundment for the beavers to dam upon rather than the culvert. However, usually a simple fence is used, similar to a Beaver Dam Analog.
When the height of the beaver damming must be limited to prevent flooding damage, a Pond Leveler pipe may be installed through the rising beaver dam.
If no ponding is tolerable near the culvert, a Culvert Protective Fence may be a better choice than a Diversion Dam.