I can tell you what I did on one of my pond and it seemed to work. It has a 12" PVC pipe and it angles down dramatically which increases velocity and capacity during flooding. I dug a pit below the outlet side of the pipe and placed a 6" drain to another downstream pond. I capped up-end of the smaller drain with a wire trash rack and filled the hole with rip rap. During heavy flow the structure spreads out the water flowing over the grass (that the 6" drain will not handle). During the rest of the time, the small drain gives the above-ground area time to grow tall grass. Tall grass lays down during flooding protecting the soil beneath. I used the same strategy on my newly finished pond (but on a smaller scale), but it has not yet been tested. I have emergency spillways on all 3 of my "fish" ponds and wish that I had them on 2 constructed wetland that do not. They were constructed by contractors and have a very level berm which has so far handled overflow. Good luck!
Last edited by RAH; 01/30/18 07:31 AM.
