VALIDATION OF A BOUSSINESQ MODEL OF BEACH GROUND-WATER BEHAVIOR

A numerical solution to the 1-D Boussinesq ground water equation is us ed to predict water table response to tidal and wave forcing. We argue that the solution presented here offers considerable advantages over other solutions to the 1-D Boussinesq ground water equation and is sim pler to apply than 2-D ground water models. The main assumption in usi ng the Boussinesq equation is that ground water flow in a shallow aqui fer can be described using the Dupuit-Forchheimer approximation, in wh ich it is assumed that changes in hydraulic head with depth below the water table are negligible. The predictive ability of the solution was tested against field data from ten wells and ten piezometers on a mic rotidal sandy beach. Two model runs were carried out: in the first the effect of tides only was considered; in the second setup due to waves was also considered. The arithmetic mean of independently measured va lues of hydraulic conductivity was used to describe sediment character istics. The piezometer data show that changes in hydraulic head with d epth are negligible for much of the beach, suggesting that the use of the Boussinesq equation is appropriate. The correspondence between mod el predictions of water table elevations and field observations is goo d for both the tide-only and the tide plus setup model runs, with the latter giving the better predictions. (C) 1998 Elsevier Science B.V. A ll rights reserved.