Mapping Infrastructure Damage After Flooding in Anambra State Using GIS

The 2022 and 2023 flooding events in Anambra State caused extensive damage to road, bridge, and settlement infrastructure across riverine communities. This study maps infrastructure damage in the Ogbaru and Ayamelum LGAs using a combination of satellite imagery change detection and field-verified damage reports. Pre-flood baseline infrastructure maps are created from OpenStreetMap data and verified Sentinel-2 imagery. Post-flood Sentinel-1 SAR and Sentinel-2 optical composites are analysed to detect damaged roads, destroyed bridges, and inundated settlements. Damage severity is classified into three categories: destroyed, significantly damaged, and accessible but flood-exposed. Results identify 14 road segments totalling 87 kilometres as inaccessible following peak flood conditions. Three bridge crossings are classified as destroyed, severing communities from markets and health facilities. The study provides a spatial damage inventory for the Anambra State Emergency Management Agency and the Federal Road Maintenance Agency to coordinate recovery operations. Keywords: flood damage, infrastructure mapping, Anambra, SAR, GIS damage assessment