This model simulates a simple stormwater detention pond with a simple discharge structure. The discharge is controlled by an orifice in the side of a metal riser as shown in the diagram below. It is assumed that the flow through the orifice controls the flow and that the outlet conduit pipe is sufficiently large and there is no tailwater to cause any backwater effect into the riser.

GoldSim is used to simulate the accumulation of water in the pond (using a Pool element) and calculate the resulting water depth using a stage - area relationship. The resulting depth is used to calculate the orifice flow. The resulting outflow hydrograph is compared to the output of a HEC-HMS model for verification of the functions.

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