Post-hurricane field survey in the wake of hurricane Irma on the British Virgin Islands - documentation and analyses of inundation parameters and hurricane sediments

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Severe storm events and related storm surges are a major threat to coastal communities and ecosystems. The current storm season with a large number of devastating storms, such as hurricanes Harvey, Irma and Maria drew renewed attention to this risk. Post-event field surveys give researchers the opportunity to directly evaluate an event’s impact on ecosystems, landscapes, and coastal infrastructures. A post-hurricane survey in the wake of Irma on the British Virgin Islands will offer the unique opportunity to study the effects of a category 5 hurricane. The low-lying island of Anegada is a highly eligible field site because it allows for a direct comparison of the effects of the hurricane and its related depositional and erosional evidence in various settings, such as reef, lagoon, sandy coast, beach ridge plain, salt pond and coastal limestone platform. Evidence could include sandy washover fans on beaches and into the salt ponds, coral rubble accumulations and coarse-clast ridges close to the lagoon, mud units in salt ponds, single clast transport on coastal platforms (coral or limestone boulders), breaching of dunes, and coastal erosion (e.g., scarps, shoreline retreat). Onshore inundation parameters (flow depth, inundation distance) will be measured, eyewitnesses will be interviewed, and any kind of erosional or depositional evidence will be documented. Aerial photos taken in September 2017 show significant coastal erosion and overwash that reached ~300 m inland on the southern shore and at least 2-3 m above sea level along the north shore.This project will take advantage of pre-event field data collected on Anegada in earlier years that allows for a detailed comparison of pre- and post-Irma data. A coast-parallel coral rubble ridge was monitored from February 2013 to March 2017. During this time span tropical storms only slightly modified the lower seaward part of the ridge. Consequently, it was proposed that the ridge may imply that the island is vulnerable to storm surges of greater impact compared to any of the recent storms. The post-hurricane survey aims to document if Irma emplaced a new ridge or if the pre-existing ridge was significantly modified or reworked.Furthermore, this study will provide new insights that can help to 1) better define characteristics of storm deposits in tropical environments; 2) identify storm units in the sedimentary record in order to set up recurrence intervals; 3) understand rubble ridge dynamics; 4) quantify the destruction of a coral reef caused by a hurricane; 5) learn about the interplay of storm surge and wave action of thousands of waves that inundate a shoreline for several hours.The project has a significant relevance in the light to climate change, most of all related to the increase in sea surface temperatures, sea level rise and the demise of coral reefs, as these processes will dramatically raise the frequency and intensity of tropical storms.