Effect of the settlement of sediments on water infiltration in two urban infiltration basins

The sealing of surfaces in urban areas makes storm water management compulsory. The suspended solids from surface runoff water accumulate in infiltration basins and may impact on water infiltration. This paper describes a study of the effect of the settlement of sedimentary layers on the water infiltration capacity of two urban infiltrations basins. In situ water infiltration experiments were performed (1) to quantify the effect of sediment on water infiltration at local scale and (2) to derive the complete characterization of the unsaturated hydraulic properties of sediments and subsoils by using the BEST algorithm. These properties were used to model the effect of sediments on 1D water infiltrations at basin scale, simulating real operating conditions for three model rainfalls (shower, rainfall and light rainfall) and the full year 2008. The results clearly prove that sediments reduce local water infiltration capacities, due to their lower saturated hydraulic conductivities (Ks). Moreover, numerical results have shown that this finding could have a drastic impact on water infiltration at the basin scale through increasing the number and duration of water pondings. From the technical point of view, this study underlines the need for efficient monitoring of infiltration basin sedimentation and its impact on water infiltration capacity.