Hurricane Idalia (2023)-induced dune erosion along west-central Florida barrier-island coast and post-storm restoration

Hurricane Idalia made landfall on 30 August 2023 along the relatively sparsely populated Big Bend coast of Florida as a strong Category 3 hurricane. Although the heavily developed west-central Florida barrier islands were not in the direct path of Hurricane Idalia, the distal passage of the storm generated a combined storm surge and high wave conditions that were favorable for inducing severe dune erosion. Since a significant portion of the studied beaches were regularly nourished, the fact that the storm impact occurred near the end of a beach-nourishment cycle exacerbated the dune erosion due to the generally narrow pre-storm beach. An emergency artificial dune restoration was started within 1.5 months after the storm impact and completed in four months. The artificial dunes were approximately 0.5 to 1.0 m higher than the natural dunes, 2.0 m-2.5 m above the beach versus 1.5 m-1.8 m above. A significant portion of the coastal dunes that were developed from the roughly 40 years of repeated beach nourishment were eroded. Degree of dune erosion can be reduced by a wider pre-storm beach and intertidal zone, in addition to the presence of a nearshore bar. Wide beach-intertidal zone and nearshore bar also improve the performance of the post-storm artificial dune restoration. A minimum of 10-m beach width at the dune base was necessary for the post-Idalia constructed dunes along the west-central Florida coast to last through the first winter. A combined beach and dune restoration would be ideal to mitigate storm impact. Management obstacles should be overcome to enable synchronized beach-dune nourishment. Emergency dune restoration alone may not be a sustainable longer-term solution.