MODELING COASTAL GROUNDWATER RESPONSE TO BEACH DEWATERING

There has been renewed interest in the use of beach dewatering as a te chnique to combat beach erosion. Although several test and prototype i nstallations have been undertaken worldwide, no guidelines are availab le to aid the engineering design of such projects. In this paper, we p resent a numerical model that simulates two-dimensional ground water f low in a coastal aquifer under beach drainage, including water table l owering and seepage face reduction. The boundary element method is app lied to solve the Laplace equation for the velocity potential. An inte rnal boundary is used to simulate drainage. We conducted simulations f or two different types of drainage systems, i.e., artificial and gravi ty drainage. The behavior of the water table from the simulations was found to be consistent with field observations. The results also showe d that the location and size of the drain affect the efficiency of the drainage system. The system efficiency slightly increases with the si ze and vertical elevation of the drain. As the drain is shifted landwa rd, the system becomes considerably less efficient. Although they do n ot represent design criteria, these results indicate considerations wh ich affect the performance of beach dewatering system.