Groundwater pressure dynamics in a laboratory swash zone

As part of the MODLIT program, which is a laboratory qualification campaign for sandy beach morphodynamics model, an instrumental study has been conducted in the LHF multidirectional wave basin (Grenoble-INP/SOGREAH, France). A key-point of the understanding of sandy beaches dynamics is the knowledge of the interactions between surface and groundwater hydrodynamics, in particular between swash and beach watertable, and their impact on accretion and erosion processes above the still water level. A dedicated cross-shore line of 9 relative pressure sensors has been deployed from the inner surf zone to the berm, combining buried and free sensors. Every sensors were located below the mean water level. Spectral analysis shows the low-pass filtering of pressure waves and allows to discriminate the low frequency modes. A detailed sequence of pressure field snapshots is presented to reveal the groundwater flows and highlight the role of swash overtopping in pressure gradients.