Modeling of sediment transport through stormwater gravel filters over their lifespan

Gravel filter media are widely used for attenuation and treatment of runoff in a range of stormwater management systems, including infiltration trenches/basins, porous pavements, and soakaways. These systems essentially reduce the effective impervious area of a catchment and also provide stormwater detention and infiltration into the surrounding soils, thus helping to restore predevelopment hydrology. Although it is well-known that these systems eventually clog and their treatment performance diminishes with time, no model developed has so far been developed to predict this behavior. The aim of this study was to develop a mathematical model of the transport of sediment through stormwater gravel filters over their lifespan. A detailed laboratory study of sediment transport was undertaken for different stormwater inflow regimes until the system became clogged. These data were used to test two models, the k-C* model (the first-order decay model) and the Yao model (a physically based model). Although these models were able to predict sediment behavior in clean filters (i.e., at the start of their life), both failed to accurately simulate observed behavior once the filter accumulated sediment. The main variables that impact the sediment process in dirty filters were quantified, and modifications to the Yao model were proposed. The modified model, with three calibration parameters, was calibrated for concentrations of total suspended solids. This model could be used in practice to asses the maintenance requirements of a gravel filter. Although developed for stormwater management, the model could be applied to a number of other disciplines, such as water treatment and groundwater recharge.