Dune Toe Collapse Risk and Mitigation

Beaches are suffering severe erosion and dune losses not only from storm events but also during moderate weather conditions. This study aims to determine the cause of dune toe collapses that frequently occur at Flagler Beach, Florida, with a focus on geotechnical characteristics and metocean conditions, and to improve mitigation strategies. The approach includes an initial desktop study about historic and current dune conditions, followed by field surveys and laboratory soil characterization, measuring geomorphological change, geotechnical properties, and metocean conditions. Field data will be used for calibration and validation of a numerical model in GeoStudio to simulate dune toe failure. Finally, the study will shift from a deterministic to a probabilistic approach incorporating uncertainty to provide better decision-aid to end users. The study will also investigate possible dune erosion mitigation strategies through slope modifications, moisture control, and changes in granulometry. The Flagler County Board of County Commissioners is the project partner, who will meet with the team quarterly and provide feedback on models for decision aid regarding efficiency and usefulness. The project will increase understanding of soil mechanics and metocean conditions regarding dune toe loss, deliver an initial risk assessment framework, and test mitigation strategies applicable to many coastal communities.