Simultaneous high frequency field measurements of water depth, flow velocity and groundwater elevation, coincident with observations of bed level change were made across the swash zone of a steep gravel beach. Groundwater oscillations were forced directly by swash events on the beachface but the antecedent elevation of the water table was important in determining the net groundwater response. The instantaneous swash flux was used as an indicator of infiltration/exfiltration and was highly asymmetric across the swash zone. A region of strong infiltration in the midto- upper-swash termed the Swash Recharge Zone (SRZ) and a transition region in the lower-swash where infiltration/exfiltration balance were identified. Morphological change over the tidal cycle was exclusively onshore and associated with berm construction. Accretion occurred close to the uprush limit within the SRZ whilst morphological change across the transition region was minimal. It is suggested that swash volume asymmetry caused by infiltration in the SRZ biases sediment transport onshore by reducing the sediment transport competency of the backwash.
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