Tyler,
I think the reason that you haven't seen much more feedback is that all anyone at a distance can do is speculate on what might work. Without topo maps, information on soil types and vegetative cover in the watershed, and runoff estimates from various precipitation events, one cannot give any firm solutions.
As I said, what you need is to get a local NRCS person or a private engineer on the site to do this work. It may cost you some dollars, but it would be far cheaper than re-building the dam. Who knows, you might have your dam placed in a location where it is not feasible, unless it is tremendously overbuilt to handle the three creek flowing into it. At least that would be my gut feeling, supported by the fact that it has washed out several times. To handle that water flow you might need a very large concrete spillway (or many large drop inlet tubes) along with 5-10 feet of freeboard up to the emergency spillway, and then another 5-10 feet up to the top of the dam.
Bill
