Numerical analysisof groundwater in a drained beach

The paper deals with a numerical simulation of the groundwater behavior inside a beach equipped with the Beach Drainage System. Two-dimensional water flow in a partially saturated porous medium has been simulated by using Richard's equations in a numerical platform (HYDRUS-2D). Numerical results are then compared with experimental ones, obtained during the laboratory tests performed on a BDS 1:1 model at the GWK flume (Hannover). The good agreement between measured and calculated results, allows to simulate different beach permeability (ranging from silt to coarse sand) and different drain altimetric positions, in order to draw some first considerations about BDS design criteria which, to date, are only based on technicians experience. In particular, a ‘limit drain depth’, strictly related to beach permeability, is defined as the maximum depth which produces the maximum water table lowering and, as a consequence, the best system efficacy in drying the porous medium inside the beach.