Detention ponds constructed in urban areas should perform two major functions: reduce flood flows and improve quality of runoff by trapping sediments and related pollutants. Providing tools for an efficient and low data–demanding assessment of pond per- formance can greatly support sediment management at the small catchment scale. This paper adopts the approach of a continuously stirred tank reactor (CSTR) to model the sediment concentration in the stormwater outflow from a small detention pond located in an urbanized catchment. The model is developed and tested using data sets of seven rainfall–runoff–suspended sediment events. Good agreement between observed and estimated outflow from the pond is achieved for both hydrographs and sediment graphs in calibration and validation. Thus results indicate that the present model due to its low data demand can predict sediment graphs at the outlet from such low-volume reservoirs.