Water balance prediction in stormwater infiltration basins using 2-D modeling: An application to evaluate the clogging process

Abstract

Sustainable urban drainage systems are built along roads and in urban areas to collect urban runoff and avoid flooding, and to filter water pollutants. Sediment collected by runoff is deposited in the stormwater basin and progressively reduces water infiltration efficiency, leading to the clogging of the basin. To help stormwater basin managers and stakeholders better understand and predict clogging rates in order to elaborate maintenance plans and schedules, water transport prediction models are necessary. However, because of the heterogeneous sediment hydrodynamic properties inside the stormwater basin, a two-dimensional (2-D) water flow model is required to predict water levels and possible overflow as accurately as possible. Saturated hydraulic conductivity (Ks) and sediment water retention curves were measured in the overall sediment layer of the stormwater basin, in addition to sediment layer thickness and organic matter content (11 sampling points). Sediment depth was used to predict organic matter (OM) content, and the OM was used to predict Ks. Water height in the basin was modeled with the HYDRUS-2D model by taking into account the sediment hydrodynamic properties distribution. The HYDRUS-2D model gave a satisfactory representation of the measured data. Scenarios of the hydraulic properties of stormwater basin sediment were tested over time, and hydraulic resistance, R, was calculated to assess the stormwater basin performance. Presently, after 20 years of functioning, the stormwater basin still ensures efficient water infiltration, but the first outflow (Hydraulic resistance, R > 24 h)) is expected to appear in the next 5 years, and clogging (R > 47 h) in the next 13 years. This 2-D water balance model makes it possible to integrate the hydrodynamic heterogeneity of a stormwater basin. It gives interesting perspectives to better predict 2-D/3-D contaminant transport.