So we were told by the city that the pond drains to the sewer. Wish I could figure out how to attach a photo or video but here's the setup:
A huge pipe that broke, brings the water and drops it onto a long narrow flat area about 3' wide x about 20' long. That is where I'd put the sediment trap. At the end of that 20' long area, there's a drop into the water. Sometimes we're able to build it up to make a good waterfall, but if the water level is high, the water drops right into the pond, and sediment starts to gather right below that drop. I actually see very little sediment going in the path of the exit drain, which is about 40' from where all the sediment sits at the drop in the pond.