Building Damage from Tephra Fall During the 2020-21 Eruption of La Soufriere Volcano

The explosive eruption sequence of La Soufrière, St Vincent commenced on 9 April 2021, disintegrating the lava domes produced during both the 1979 and 2020/21 effusive phase and carving out a new crater geomorphology. The explosive events resulted in plumes to greater than 15 km above the volcano with tephra fallout affecting all of the island of St Vincent as well as Barbados to the east and the French islands to the north. The eruption resulted in significant building damage, including collapse, in the northern part of the island.  

Empirical impact data are one of the most important sources of information for impact forecasting, and yet only three published datasets of structural tephra fall damage to buildings exist (Pinatubo 1991; Rabaul, 1994; Calbuco, 2015). Such data provide an evidence base from which advice on future impacts and mitigation strategies can be developed for communities living close to the volcano. Furthermore, damage data collected following an eruption can be used for developing vulnerability functions needed in quantitative risk assessments, to support emergency preparedness and response.  

The explosive events from La Soufrière in April 2021 provided an opportunity to assess damage from the extensive tephra deposits, with a view to using the empirical impact data to develop vulnerability functions tailored for a regional context. A ground-based impact survey was undertaken in August 2021 that captured 500+ buildings in settlements surrounding the volcano and encompassing a wide range of building types and construction materials. We provide an overview of the damage to buildings and identify key advice for mitigating future impacts. Drawing from the lessons learned, we examine future strategies for collection of impact datasets during such events.