Investigation of Flood Vulnerability of Low-Income Residential Areas in Port Harcourt, Rivers State

Low-income residential areas in Port Harcourt, South South Nigeria, experience frequent and damaging flooding events attributable to inadequate drainage infrastructure, rapid urbanisation, and low-lying coastal topography. This study investigates the flood vulnerability characteristics of three low-income residential communities in Port Harcourt: Rumuola, Diobu, and Borokiri. A field-based descriptive approach was adopted, incorporating topographic surveys using differential GPS, assessment of existing drainage infrastructure capacity, and structured questionnaires administered to 200 households. Remote sensing analysis using Sentinel-2 satellite imagery was used to map land cover changes from 2013 to 2023. Drainage network capacity was calculated using the rational formula against storm return period rainfall intensities derived from local meteorological data. Results show that existing drainage systems are designed for a 2-year return period storm while current land cover conditions generate peak runoffs consistent with a 10-year storm event. Drain blockage by solid waste reduces effective drainage capacity by an estimated 45 percent. Land cover analysis reveals a 34 percent increase in impervious surfaces over the ten-year study period. Flood depth records from household interviews indicate inundation events exceeding 0.5 m in 58 percent of Rumuola households annually. The study concludes that integrated flood risk management combining drainage upgrades, solid waste management, and urban land use regulation is urgently needed. Recommendations include the adoption of urban flood risk mapping as a mandatory component of building permit processes in Port Harcourt.

Keywords: flood vulnerability, urban drainage, low-income housing, Port Harcourt, South South Nigeria