Why aren't the maximum flow values on my depth-flow curve outlet structure being followed in the downstream pipe when I have a large backwater condition?
This may occur when the downstream conduit that the flow is coming into is not large enough to accommodate the backwater condition present. For example, let's say there is an elevation-area curve on a Pond that has a constant elevation of 500 ft. for every area entry. Downstream of that pond the flow goes into a conduit we'll refer to as CO-1 that has a start elevation of 480 ft., a stop elevation of 479 ft. ,and has a control structure with a user defined depth-flow curve. Downstream of CO-1 there is another conduit, CO-2, where the maximum flow values defined on the depth flow curve from CO-1 are not being adhered to. CO-2 is probably has too small a diameter to accommodate the flow being supplied due to the large backwater condition.