Infiltration trench is one of the best stormwater management practices to control excessive runoff volume in urban areas. Most of the methods or models employed for designing an infiltration trench are either very simplified which leads to unreliable results or suffer from inconsistency of using one equation in variably saturated soil. Therefore, in this paper, the authors have developed a new onedimensional infiltration trench model based on Richards’ equation for modeling flow movement in variably saturated soil, coupled with a surface water balance equation as the upper boundary condition, using implicit finite-volume method. The proposed model allows for periodical ponding in the storage, interaction between storage and subsoil, and flow movement in variably saturated soil beneath the storage. The model was run under different scenarios and tested against several experimental and analytical test cases. The obtained numerical results were mass balanced and exhibited accurate simulation of the flow movement in unsaturated soil as well as ponded infiltration in a saturated controlled experimental trench

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