it worked below the dam to keep it from washing out from high water, but above the dam, no, when we get high water, enough to flood, the rock keeps the bank intact but does not hold the water. I should point out that as the river is right now, it is about 50 -60 feet wide. BUT like i said during the time that the flood gate was damaged and above the dam was drained, it was about 15ft wide and 1ft deep. Incidentally this is also about 15-20 miles UP river from where last year a earthen dike along side of a different dam was washed out totally draining the lake above it. and in doing so also lowered the level of the river clear up to where the proposed site is now. Here is a link of wher the dam was breached last summer, like I said 15-20 miles down river from where we are talking about. I am agree with an earlier post about not repairing that one. because it was privately owned.
delhi dam - Google Search