Observations of Water Content and Fluid Pressure within the Interior of an Eroding Beach Dune

Existing parameterizations for predicting dune morphology do not include the mechanics of water movement within dune interiors during erosion events. Sediment moisture content influences sediment behavior and consequently influences the behavior of dunes as they erode. We instrumented the interiors of vegetated, bare, and biocemented dunes with 30 moisture sensors and 15 pressure sensors during a large-scale beach dune erosion experiment in the OH Hinsdale Wave Research Laboratory Large Wave Flume. The sensors were vertically stacked at 8 cross-shore locations with an approximate vertical spacing of 30 cm and cross-shore spacing of 3m. The 1:2 scale dune was subject to hurricane waves and water levels scaled from Hurricane Sandy. A line-scan LiDAR was used to capture runup heights and erosion along a single transect throughout the duration of the experiment. Using this combination of sensors, we quantified the movement of water in the dune throughout the storm, pressure gradients and infiltration caused by runup events, and the influence of pressure and moisture content on the mechanics of dune erosion. Erosion volumes are correlated with individual runup events and their associated sediment moisture content for each dune archetype. Preliminary results indicate that moisture sensor data can identify shifts in erosion regime and that moisture is modulated differently between the dune types.