Flooding is one of the most persistent environmental risk facing Lagos.

The PALM-TREEs study finds that flooding occurs annually in two broad periods: the June–July floods, associated primarily with extreme rainfall, and the more severe September–October/October–November flooding, influenced by lagoon surges and spillway discharge from the Ogun River Basin. The latter can persist for weeks depending on the volume of water released from the dam. Flood risk is particularly high in informal and vulnerable settlements, including Ajegunle, Ijora, Agege, Ikorodu, Ifelodun, Mile 12, Bariga and Agboyi-Ketu. The study also identifies drainage blockage, particularly by waste debris, as a major factor amplifying flood impacts, with 65% of research participants identifying blocked drainage as a contributor to flood damage. Conversion of floodplains to grey infrastructure was also identified as a driver of flooding in island settlements, where flooding can occur annually and persist for two to three months. The consequences extend beyond physical damage.

Flooding results in displacement, loss of property and livelihoods, disruption of services, and health risks, including cholera and malaria. Communities respond by relocating to relatives in upland areas, constructing embankments, renovating drainage, moving valuables, temporarily closing schools, and controlling erosion.
These findings reinforce existing evidence that Lagos’ flood vulnerability is shaped by the interaction of its coastal and low-lying geography with rapid urbanization, inadequate infrastructure, drainage constraints, and poor land-use management.
Importantly, Lagos already has a substantial policy foundation for addressing these risks. These include the Lagos Resilience Strategy, the Lagos Climate Action Plan, and more recently, the Lagos State Climate Adaptation and Resilience Plan (LCARP).
The central policy challenge is therefore not the absence of flood-management policies, but ensuring that existing measures are targeted towards the communities and locations experiencing the greatest exposure and vulnerability, while addressing the environmental and governance factors that amplify flood impacts