Oceanic Pulse Forcing of a Beach Groundwater System

Abstract

This paper presents the findings of a pilot study into oceanic pulse forcing of a sandy coastal aquifer. Field observations of the response of the aquifer to a wave setup induced pulse in shoreline levels reveal that the pulse penetrates further into the aquifer than the semi-diurnal tidal signal. The data are then used to evaluate the abilities of an existing analytical solution and a numerical model to predict the propagation of the pulse in the interior of the aquifer. Both the analytical and numerical models predict the growth of the time lag with landward distance of the pulse adequately but fail to reproduce the decay of the pulse, significantly over predicting the decay rates. In this instance, the presence of tidal fluctuations and a sloping ocean boundary have been eliminated as potential causes but another possible candidate that warrants further investigation in the future is the infiltration from wave runup which would act to increase groundwater levels.