In order to protect sandy beaches from erosion caused by waves, a Beach Management System (BMS) is planned in some areas along the Japanese coast. In order to predict the flow in the extended unsaturated zone due to increased drainage, numerical simulations were carried out for a laboratory aquifer and the cross section at a test site in Chiba Prefecture, Japan. The numerical simulations revealed that the unsaturated zone extends below the sandy beach and that salt and fresh water mixed around the drainpipes.
