Airwreck,
I was thinking more of a spot in the dam that was just lower than the rest, shallow enough to drive through and deep and wide(long) enough to evacuate the amount of overflow. Culvert would work just a little more work and expense. Mine is 6 or so feet wide and drains into a 6" pipe in the back, the back is also lower than the sides in case of a really big rain.
I lose fish all of the time, most, usually as the waters first goes over the spillways edge, most are small couple of weeks old. The tilapia reproduce rapidly enough to cover any of the loses. Trying to prevent lose might cause more harm than good as debris can clog your spillway.
