NyQuiLlama,
A couple of thoughts by way of follow up. Seriously consider the trash pump to lower your water levels. This will accomplish two things: 1) it will make the entire operation safer and 2) it will enable you to see other damage from the critters. Thats damage that you may be able to repair all at the same time. The roofing material may help with spillway maintenance, but I doubt it will have any help with the critters...but I could be wrong.
Critter damage, in my experience, is much like an iceberg...what you can see is only a small part of the real damage. Take this opportunity to find and repair all the damage and you won't regret it. Good luck and keep us posted.
