Daryl:

If you haven't seen it already, look at both links in this archived thread:

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=92487#Post92487

I think in #590 there is a formula to calculate the flow of water over your emergency spillway, so you don't exceed "X" flow speed, which creates washouts. i.e. it will tell you how to figure out your emergency spillway size.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).