After years of renting, I purchased my first home for the princely sum of $30,000. There's a small stream running through the very back of the lot, and at the time, the stream bank was awash in blackberry and English ivy, likely a result of bird transport. Over the years, I removed all of that stuff; replacing it with sword-ferns and alder. It became a nice little wildlife-watching spot.
And then Portland's Bureau of Environmeddle "Services" slapped an "environmental overlay" on the place and sent me some 200+ pages of dead tree, informing me - among other things - that they could now enter "my property" at any time, that I could plant no non-native species within 50 feet of the stream (including garden vegetables), and that I would have to apply to them for permission prior to making any changes to the property. At the time they did this, I had plans to replace the back deck on the house, which was literally falling apart.
BES informed me that I'd have to hire an architect and submit drawings to them with a $1200 nonrefundable fee, after which they would at some point tell me whether or not I could replace the deck. That about did it for me. Screw it; I took out the old deck and put in a new one anyway. I'd really had about enough of BES by then. I was able to peddle the place, and got $140,000 to apply toward purchase of a different home, up in the hills and, to date, far away from BES.
Before we moved, we'd identified some 120 unique bird species, including two species of heron, wood ducks (stream), quail (brush) a variety of woodpeckers (including pileated), hawks, owls, etc. I left dead trees near the stream standing as snags for habitat.
Shortly before the BES overlay, beavers moved in back there and built a dam. This created some consternation amongst upstream neighbors; in part due to rising water levels and in part due to tree losses. One neighbor showed up at the door to talk about "my beavers".
Having some years of experience in wild animal management, I met with concerned neighbors and advised them to place poultry netting around the base of any trees they didn't wish to lose, to a height of three feet. This humanely deters beavers.
As for the water levels, that was a bit more problematic; you can't just chop holes in the dam, as the beavers repair them overnight. And although the property was located between SW Shattuck Road and SW 45th, no public agency was willing to relocate beavers.
So I met with those folks, and we established a higher water level that they could live with, and I set about making that happen. I went to Home Depot and picked up 8 feet of 4" PVC pipe, and a couple of elbows to fit. Back at the ranch, I hauled out my trusty axe and chopped a hole through the dam, dropping the water level to our agreed-upon standard.
I placed an elbow on each end of the pipe, facing downward, and weighted it into the cleft. The beavers cemented it into place overnight. Bingo. Everybody happy - peaceful coexistence. Well, the beavers would possibly have preferred to keep raising the water levels, but....
The neighbors lost no more trees after installing the netting, and were satisfied with the water level. Oh, and simply inserting a pipe into the cleft won't work; that's why you need the elbows: beavers are attracted to water flow, so the back elbow needs to direct water quietly down the back of the dam. The pipe, jutting out into the middle of their pond, would be plugged by them as well, hence the downward-facing elbow at that end. They can't figure that part out.