Evaluation of Settlement Encroachment into River Floodplains and Land Use Transformation, A Four-Decade Geospatial Analysis of the Ngadda River Corridor, Maiduguri, Nigeria

Abstract

Settlement encroachment into river floodplains represents a critical challenge to sustainable urban development in rapidly growing African cities. This study examines the spatial patterns and environmental implications of settlement expansion within the River Ngadda floodplain in Maiduguri, Borno State, Nigeria, spanning the period 1985–2025. The research adopts a mixed-methods approach, integrating geospatial analysis of multi-temporal satellite imagery Landsat 5 TM, Landsat 7,8 & 9 ETM+ were used, with structured questionnaire surveys (n = 381) and field observations. Land use/land cover (LULC) transformations were quantified using ArcGIS 10.5, with GPS-facilitated ground-truthing ensuring classification accuracy. Results indicate a substantial transformation of the floodplain landscape, as built-up areas increased from 20.3% in 1995 to 54.9% in 2025, representing a 63.19% expansion. In contrast, vegetation declined from 46.4% to 24.0%, alongside significant reductions in bare surfaces, reflecting the loss of natural land covers. Additionally, water surface area increased by 172.38%, suggesting intensified flooding linked to reduced infiltration and increased surface runoff. Survey findings further reveal that 75% of respondents perceived continuous settlement expansion, while 80% reported increased flood frequency and intensity. Population growth and weak regulatory enforcement were identified as major drivers of encroachment. The study concludes that persistent floodplain encroachment has degraded ecological integrity and heightened flood vulnerability. It therefore recommends strict land-use regulation, integrated floodplain management, and sustainable housing strategies to enhance urban resilience.