Land Subsidence Hazard and Building Collapse Risk in the Coastal City of Lagos, West Africa.

Every year incidents of building collapse claim many lives and cause enormous financial losses around the world, which are often blamed on low‐quality materials, non‐compliance with standards, lack of oversight, and failure to enforce building codes. Here, we highlight the role of land subsidence in triggering unprecedented collapses in the city of Lagos, Nigeria, which has reported over 200 casualties during 152 building failures since 2005. We used acquisitions from radar satellites for 2018–2021 and provided data that link subsidence to foundation damage and high building failure risk in the region. We estimate that an area of 5–81 km2 and 255–4,000 buildings are exposed to a high to very high risk of collapse for short‐term (10 years) to long‐term (75 years) periods. Differential land subsidence can trigger building collapse, and the data presented here will enable authorities to create adequate building codes and standards and devise mitigation strategies. Plain Language Summary: Low‐quality materials, non‐compliance with standards, a lack of oversight, and failure to enforce construction codes are frequently cited as causes of the annual global increase in building collapses that kill countless lives and result in tremendous financial losses. In this article, we focus on the impact that land subsidence plays in causing building collapses in Lagos, Nigeria. We employed radar satellite acquisitions from 2018 to 2021 to present evidence linking subsidence with foundation damage and a significant risk of building failure in the area. We calculate that in the future, between 5 and 81 km2 and 255–4,000 buildings are at a high to very high risk of collapsing. Key Points: Major parts of the city of Lagos are subsiding at rates of more than 4 mm/yrOur analysis suggests a causal relationship between incidences of building collapse and differential subsidence in LagosBy 2053, a total area of 45 km2 and approximately 2,200 buildings will be exposed to a high to very high risk of collapse [ABSTRACT FROM AUTHOR]