Mapping Flood-Prone Zones in Port Harcourt Using GIS and Digital Elevation Models

Flooding constitutes one of the most recurrent and economically destructive natural hazards in Port Harcourt, Rivers State, exacerbated by low-lying topography, inadequate drainage infrastructure, and intense seasonal precipitation. This study maps flood-prone zones in selected communities within the Port Harcourt Local Government Area using Geographic Information Systems and a Digital Elevation Model derived from Shuttle Radar Topography Mission data. Hydrological terrain analysis, including sink filling, flow direction computation, flow accumulation, and watershed delineation, is performed in ArcGIS to identify areas susceptible to surface water ponding and inundation. The resulting flood susceptibility map is validated against historical flood event records obtained from the Rivers State Emergency Management Agency and field survey observations. Findings indicate that low-elevation zones along the Woji and Rumuola corridors exhibit the highest susceptibility, with over thirty percent of residential parcels in these areas falling within the high-risk class. The study further highlights the spatial correlation between impervious surface expansion and elevated flood risk, underscoring the role of unregulated land development in aggravating urban flooding. The outputs of this analysis are intended to inform the Port Harcourt Metropolitan Development Authority in prioritising drainage infrastructure investment and enforcing flood-plain building setbacks. The study contributes methodologically to flood risk assessment frameworks applicable across the Niger Delta region. Keywords: flood mapping, GIS, DEM, Port Harcourt, flood susceptibility.