Controlling the hydraulic impact of discharge from storm water detention ponds into streams

Traditionally storm water detention ponds in Denmark are discharging to steams with a constant flow rate based on standard values. The discharged flow rate does not necessarily take the stream characteristics into account, thus sometimes causing flooding and erosion of the stream. Based on knowledge of the geometry and sediment characteristics in the stream it is possible to determine the maximum capacity of the steam to receive detention pond discharges without unintended erosion of the stream and flooding of the adjacent areas. Results of modelling have shown that it is possible to make a controlled discharge of storm water that is in agreement with the hydraulic capacity of the stream.