I am facing the same scenario. 60 year old 1/4 acre pond, 20+ acres of wartershed, recently renovated will be stocked this year as soon as it fills up and overflowing is not likely until the fall. One 4" rain event and I might put the emergency overflow to use. I hope to give the stocked fish as much opportunity to spawn before the dam is overrun possibly latter in the year, bumping up the number of fish in the pond.
My goals are to have a decent BG/RES pond with stunted LMB and maybe ladder stocked HSB as predators. It is likely that my 1/4 acre pond will want to overpopulate due to lack of culling. My thoughts are that the occasional overflowing (once or twice a year)could help with overpopulation (natural culling).
I sacrificed a couple of feet of full pool depth by keeping my drain pipe at ten feet while giving the dam 3 feet of freeboard. This should help a little during high water events by allowing water to build up over the drain pipe by 3 feet before the emergency overflow is breeched. Some fish will leave through the pipe, but maybe not as much as over the top of the dam.
I will be hanging my hat on the hopes that the majority of my fish will not abandon my pond and what does swim over the top will only reduce the possibility of overpopulation/stunting (and the creek will profit from the extra renegade fish).
