Wisconsin has had a beaver vacuum for a number of years in many areas, by state design, which is kind of sad, not normal. Surprised the animal people don't point it out. Beaver can be a real problem when fur prices drop, so highway departments must be saving, but it is an abnormal environment. Heard the same thing about the trout. It can be difficult to maintain a balance, keep "some" beaver because they are rodents that are very prolific, reproducing quickly. In N.Y they figured they would nearly more than double every three years if left unchecked in the Adirondacks, 100 beaver becoming about 220 and nearly 500 in six years. With milder winters and better feed they double even faster in outlying areas.
Back to precipitation. On one really wet year I got quite a surprise. Clients often ask, "if we trap them will they come right back?" I usually would tell them if we cleaned up the issue we were good for the year, which had, until that time, always been the case. One very wet summer I had two locations that each required trapping 5 times, new pairs moving in over and over again after heavy rains. In-between I would ask, "was there any activity after I trapped." Each time the answer was no. For a period of three to four weeks it would be completely clear, no damming, then start all over again.