MEASUREMENT OF GROUNDWATER AND SWASH INTERACTIONS ON A SANDY BEACH

摘要

Beach groundwater is a complex and dynamic system interacting with tides, waves and swash. Groundwater fluctuations driven by oceanic oscillations enhance water exchange between the ocean and coastal aquifer. This alters total submarine groundwater discharge (SGD) rates and the breakthrough concentration and exit times for contaminants entering coastal waters. Interaction between swash dynamics and groundwater may also be important with regard to onshore sediment transport and beach profile evolution (Horn 2002). There is currently limited understanding of how the beach groundwater system responds to oceanic forcing at various frequencies. This paper presents field measurements collected on Belongil Beach (Byron Bay, NSW, Australia) during the period between 12th and 25th June 2004. Data includes piezometric head measurements from a crossshore piezometer transect and vertical head gradients from transducers installed in nested piezometers. The data is discussed in terms of small amplitude groundwater theory and indicates similar magnitudes of horizontal and vertical flows in the intertidal zone. The latter are frequently ignored in beach groundwater models.