Beavers need to have a home. Ideally, they like to build it in the middle of the pond so it's surrounded by water, but if that's not possible because the water is too deep, they will dig a home into the ground next to the pond with the entrance under the water so you can't see it. They don't really care if it's the dam or not, but since the slope of the dam is usually steeper then the rest of the pond, it becomes very attractive to them to dig there. Large earthen dams all have rip rap, or large chunks of concrete from the bottom of the dam all the way to the top to stop animals from digging into the dam. It also helps with erosion, but erosion is only at the surface of the pond, the underwater part is to stop digging.
I grew up water skiing in the SF Bay Area Delta, from Tracy to Sacramento. At one time, I knew all the main channels and where all the best places to ski where regardless of the wind, and where to party. California is a state with very restrictive hunting laws on everything except beavers. When I was there, you could shoot them with any weapon you wanted, any time of the day or night, every day of the year, and you could use spot lights to shoot them at night. There was no limit on how many you could shoot. Levi breaks happen a few times a year and they are always because of beavers getting past the concrete rip rap and digging their homes into the levee's. Eventually, they go too far and the water pushes through, then very quickly, the entire levee busts open.
On my pond, there is a creek behind my dam that flows to the Sabine River. Beavers travel up and down that creek, and dam it up in places. I guess that some make their homes in the banks, which are steep and well protected. I also figure that one day, one will do the same in my dam. They have taken down hundreds of trees, and every single rose bush at my gazebo. Who knew they ate rose bushes? But after it happened, I found out that they eat every woody type plant. In the last ten or twelve years, I've shot about 8 of them, and my wife has taken a couple too. If we see it, we shoot it. At 200 yards, it's a heck of a shot to heat the top of the head as it's moving across the water. If you miss, just wait, they will pop up again somewhere else.
Never assume, or hope for the best. Eventually you will regret it.