Assessment of Sub-Watershed Contributions to Flooding in Magarya Catchment, Gombe Metropolis, Gombe State, Nigeria

Abstract

This study investigates sub-watersheds role in contributing to flooding events within the Magarya Catchment, located in Gombe Metropolis, Nigeria. The primary objectives were to delineate sub-watersheds, calculate runoff coefficients, and estimate peak discharges using GIS techniques that integrate digital elevation models (DEMs), land cover data, soil classifications, and rainfall data. The results identified six delineated sub-watersheds ranging from 2.56 to 22.63 km², with composite runoff coefficients varying from 0.31 to 0.61. Peak discharges ranged from 15.00 to 156.90 m³/s, with Sub-Watershed 3 exhibiting the highest peak discharge. Cumulatively, Sub-Watershed 6 manages a combined runoff of 743.08 m³/s, highlighting critical flood protection needs. The study underscores the potential of Nature-Based Solutions (NBS) in mitigating flood risks. Recommendations include implementing targeted flood management strategies such as reforestation in Sub-Watershed 6 to enhance soil permeability and reduce runoff and restoring wetlands in regions with mixed land use to buffer peak flows and improve flood resilience. Future studies should focus on continuous monitoring to inform adaptive flood management practices, integrating NBS to promote sustainable water resource management and enhance community resilience to climate change impacts. Keywords: Flooding, Sub-watershed, Runoff Coefficient, Peak Discharge and Magarya