Moisture likely plays a significant role in how coastal dunes change and erode, but moisture-related processes are often overlooked in studies about dune evolution. Previous research indicates that the dune slumping is primarily controlled by wave infiltration into the dune, and subsequent moisture effects on dune stability. When water infiltrates the dune, it increases the internal moisture, adding weight and potentially leading to collapse if the destabilizing forces become stronger than the dune’s ability to hold together.

However, few studies have examined the complex ways moisture levels in dunes can change over time and across different areas. This includes looking at how swash (the water that rushes up the beach), groundwater, and rainfall contribute to moisture levels. We still don’t fully understand when and how different parts of a dune get wet or which environmental factors have the biggest impact on these moisture changes. Gaining insights into these moisture dynamics could help us understand how they affect the erosion of dunes.

The objectives of this study were to 1) quantify variations of internal dune moisture content; 2) constrain the environmental variables responsible for those changes; and 3) assess when dunes are most susceptible to erosion as associated with internal moisture dynamics. The resulting data improve understanding of dune dynamics and help determine the capacity of internal moisture to influence erosion.

We found that internal dune moisture is highly variable in time and space, which likely affects the erosion potential of the dune. The spatial variability in internal dune moisture is influenced by local environmental forcings (like tidal stage, rainfall). The temporal variability in moisture content reveals both strong seasonality and complex wetting and drying patterns at the event timescale. The spatial and temporal variations in the total moisture content within dunes have important implications for “priming” dunes for erosion.

This work was published as “Linking Internal Coastal Foredune Moisture Dynamics to Erosion Vulnerability” in the Coastal Sediments ’23 Conference Proceedings, which can be found here. A pdf is also provided below for your convenience!