Assessment of building damage from tephra fall during the 2020-21 eruption of La Soufriere volcano

Empirical impact data on how the built environment responds to volcanic hazards is vital for improving our understanding of how societal assets may respond during future eruptions and to provide an evidence base for both qualitative and quantitative risk assessments. The explosive eruption of La Soufrière, St Vincent, in April 2021 generated eruption plumes extending 15 km above the volcano, with tephra fallout affecting the whole island of St Vincent as well as nearby islands.

The eruption resulted in significant building damage, including collapse, in the northern part of the island. A ground-based impact survey was undertaken in August 2021 with a focus on buildings located in the “red” - very high hazard - zone that sustained the heaviest impacts during the eruption; nearby settlements in the “orange” - high hazard - zone, which were impacted less by tephra deposition, were also incorporated. Over 500 buildings were catalogued in settlements surrounding the volcano, encompassing a wide range of building types and construction materials.

A building typology comprising seven categories was developed to characterise each structure, with the majority of assessed buildings having unreinforced concrete block walls and sheet metal roofing. A tailored damage framework was used to categorise each structure and mitigation strategies, both long and short term, were captured. This analysis provides an evidence base for advice on future impacts and mitigation strategies relevant for communities living close to the volcano in St. Vincent and on other volcanic islands in the Caribbean.