I had the same problem when I first purchased my 160 acre property.....the "beavs" had gone unchecked for a few decades and as a result built two super-dams that subsequently flooded about 10-15 acres of farmland....it was basically a lake...great for duck and goose hunting but it actually cut me off from accessing about 30 acres of prime wooded and hunting land...essentially the back 3rd of the property....also, they were killing scores of huge viable trees just to get at the top branches for food....the rest of the tree just rots.....what they had actually dammed was a municipal drain that runs right down my property.....the drain superintendent got involved and the bottom line is that they encourage land owners to take action on their own property to take care of the problem by "relocation" of the varmints....especially in my case as this was also causing other problems upstream on other properties.....so the green light was given...it was spring-time....we proceeded to manually break down a 5-6 foot opening at mid-point of the dam, enough to cause a major drainage of the flooded area...this worked great to bring the water level down...of course as most of us who have dealt with a beaver problem before know, these critters are not only destructive but also industrious little buggers....the first thing that happens is the "re-construction crew" shows up around 7 PM to fix the leak....the dispatch crew (that's us) wait for them to arrive and proceed to send them to heaven....accelerated lead poisoning.....about 20 beavers over the span of about 2 weeks.....any remaining beavers got the hint and left, never to return....the entire area was drained, dried and is now green again....trapping works too but it's a lengthy and less effective process than a .22 mag. Unless you do it this way, as PILOON said, you'll never win....in the province of Ontario you don't need a permit to scare away, capture or kill most wild animals, if the animal is causing damage to your property, unless the animal is on the endangered or threatened species list....beavers are not on the list for obvious reasons...overpopulation....some people like having beavers around.....I don't.....this is the way the landowners in my neck of the woods take care of the problem.