Effects of seepage flow on swash zone sediment transport

Coastal groundwater regimes have a significant impact on the near - shore sediment transport and beach stability in coastal areas. Groundwater head fluctuation caused by the swash uprush and backwash influence the swash zone sediment transport in a sloping beach. It is important to understand the response of groundwater to the swash wave motion. Only few studies have been attempted previously perhaps because of the complexities of the problem, such as solving the water table free surface and handling complex boundary condition like water fluctuation caused by run-up and run-down of the swash wave front. Also in order to model the transient behavior of groundwater in response to swash motion, a very short time step should be applied and this causes a need for enormous computational effort. The groundwater behavior under the influence of swash motion in an unconfined coastal aquifer with a mild sloping face in mostly affected by two factors: the infiltration of seawater from the top of the beach slope into the aquifer at maximum run up, and exfiltration of groundwater during run-down. The latter effect is intensified by a mild-sloping beach and due to the existence of a seepage face. The objective of this study is to investigate the groundwater dynamics of an unconfined coastal aquifer under the influence of swash uprush and backwash motions. A two - dimensonal time dependent computational model is developed considering the dynamic boundary of the swash motion at the beach face. The findings will be further applied to simulate the swash sediment transport.