I'm renovating a 45 year old dam located in southeastern South Dakota. It originally covered 12.89 acres and held 33.83 acre feet but is now silted in. I think we can end up with about a ten acre lake with most of the depth in the eight foot range and 2 acres in the 15 foot range. Since we have so much silt to move, it seems that the best way to do this is to make deep channels and domes/ridges that would be about two feet below the high water mark. We have an 883 acre watershed composed of half pasture (grass) and half cropland (beans, corn, and alfalfa) so we think that the lake will stay full most of the time. The surrounding terrain is fairly open so there will be quite a lot of wave action (especially in the summer with strong south winds). The maximum straight line for wind to act on is about 400 yards.

I have two questions. How deep to we need to make the channels to avoid huge amounts of submergent vegetation? How far down underwater does the erosive action extend? I don't want them to wash the tops of the domes/ridges back into the channels.

The dam itself is in good shape. Any other ideas would be greatly appreciated.
Thanks
Mike