Modelling of flow pattern and particle removal in an open stormwater detention pond

Paper in proceeding, 1998

In Sweden open stormwater detention ponds are more often used to reduce stormwater pollution through sedimentation. The pollution reduction occurs both during storm events and in between events. Design methods are often simplified and based on detention time only. However, not only the pond volume but also the geometry and thus the flow pattern are of concern when designing open detention ponds. In the city of Göteborg a 6200 m2 open stormwater detention pond was investigated with respect to massflows of pollutants and flow pattern. The observed data has been used to verify a FEM model established for the pond. Both 3-D and 2-D flow simulations have been performed at inflows starting at 20 l/s up to a maximum of 800 l/s. The simulations show that both 2-D and 3-D calculations give reasonable agreement with observed data. The 3-D calculations are however more accurate taking the bottom shape into account. Conclusions drawn from this study is that simulations of pond flow pattern are essential in designing pond geometry, and inlet and outlet locations.