Paul Young5 said:Those little critters—muskrats, nutria, or whatever you want to call those river rodents—they dig these tunnels, and let me tell you, those tunnels are the absolute worst enemy for levees; once the water gets a hold of them, it's game over. For a levee to actually work properly, it needs time to settle and compact, which takes quite a while, so instead of just dumping loose dirt in front of the water, you really ought to be using sandbags. Honestly, anyone who genuinely believes you can just "defend one side of a river" with nothing but an excavator—and please, don't take this personally, I'm just speaking my mind—is sorely mistaken. And if you actually want to defend anything effectively, you need to understand hydrology, because by the time a river starts overflowing its banks, it’s already far too late.
Now, look, I know exactly what I'm talking about here,
those tunnels created by rodents have to have an outlet that runs from the river through the levee to the dry side, and that's where the water flows through, widening the hole via erosion. Once that hole gets wide enough, the whole damn dam just erodes away—it breaches.
If we had focused on protecting the levee—that is to say, preventing those erosion holes from expanding—the levee would still be standing.
I do agree with part of what you said, though, regarding the fact that once a breach actually occurs, there's no saving it, because at that point, nobody can stop the sheer pressure of the water. All you can really do is use excavators to dig diversion channels so the incoming floodwater flows into the areas you've designated to be flooded, which might eventually help mitigate the overall damage.
The holes dug by mice or crayfish are actually the most dangerous things for a dam, and that's precisely why they sometimes have to treat the water in reservoirs—like that one near the old site—specifically to prevent crayfish from digging those channels right into the levee structure.
That particular dam is made of clay, which is basically a playground for creatures looking to dig holes, making the situation incredibly precarious. Back when those insurgents mined the dam, they actually managed to prevent massive erosion because crews were able to immediately get in there with excavators and dump trucks to fill in the eroded areas.
So, you see, it actually *is* possible to save a dam with an excavator if you act fast enough.☕