A Framework for Assessing Computer Models for Sediment Transport and Accumulation in Wet Detention Ponds

In urban areas, soils and other particulates can be picked up by and suspended in stormwater runoff as it passes over the landscape. If this runoff water is routed through a stormwater pond some of these particulates settle out of the water and onto the bottom of the pond. Stormwater ponds accumulate sediment, regardless of whether this is a primary function or not, and many municipalities are encountering large costs associated with controlling sediment in ponds, especially if frequent dredging is needed.

The ability to predict sediment transport and accumulation in stormwater ponds would provide needed information to support operations and maintenance decisions, such as the frequency of dredging, and to design (or re-design) ponds to reduce operational costs. The rate of sediment accumulation in a pond depends not only on several processes including runoff flow patterns into the pond, dynamics of the particulates suspended in the stormwater, and the flow of water within the pond, but also on the physical characteristics of the pond as well as any stratification occurring for variables such as temperature, dissolved oxygen and salts. These complex and interacting processes are difficult to observe and model.
Currently, there exist computer models that have the potential to simulate sediment transport and accumulation in stormwater ponds but there is no straightforward means of assessing whether a given model (or set of models) is appropriate for this purpose. Presented in this paper is a framework to assess these models so that municipalities can either (1) specify the computer model that is to be used for pond designs or (2) evaluate the adequacy of models that are used by proponents in their design submissions. With this framework in place, municipalities can choose the computer model(s) that best suit their needs for sediment management in their stormwater ponds.