Swash Seepage Velocity Estimation using Image Analysis

In the swash zone, the vertical flow of water into and out of the bed is one of the factors that may affect the surface sediment transport. To understand swash zone hydrodynamics, detailed measurements of swash front velocity were obtained in the swash zone by image analysis. During wave up-rush, surface water, in general, infiltrates generally perpendicularly into the beach and deflects direction when reaching groundwater table. Swash velocity plays a significant role in the up-rush infiltration process, which can be divided into three stages and positively related to the surface infiltration. As for the subsurface infiltration rate, it decreases rapidly and reaches a steady rate at the end. It is confirmed that swash front velocity can modify the infiltration process and its influence decreases towards the up-rush end. Calculated infiltration rates after incorporating the influence of swash front velocity into Darcy's law fit closely with the measurements.