Spatial assessment of accelerated surface runoff and water accumulation potential areas using AHP and data-driven GIS-based approach: the case of Ilorin metropolis, Nigeria

• Published in: Geocarto international 2022-12, Vol.37 (27), p.15877-15895
• Main Authors: Idrees, Mohammed O., Olateju, Sanni A., Omar, Dahir M., Babalola, Ayo, Ahmadu, Hussein A., Kalantar, Bahareh
• Format: Article
• Language: English
• Subjects: erosion; GIS; hazard; Ilorin; multicriteria analysis; Urban flood
• ISSN: 1010-6049; 1752-0762
• DOI: 10.1080/10106049.2022.2102236

This study assesses and maps accelerated surface runoff and water accumulation hazards in the Ilorin metropolis (Nigeria), using topographic and climatic variables that control accelerated surface runoff and water accumulation. Regarding the accelerated runoff, profile curvature, tangential curvature, drainage density, slope length (L-S) factor, convergence index, catchment shape, land use, and rainfall data were utilized. For the water accumulation process, surface slope, topographic wetness index, drainage density, convergence index, elevation, and altitude above channel were considered together with rainfall and land use. In each case, criteria weights were computed using Multi-Criteria Decision Analysis (MCDA) technique and subsequently integrated into the GIS environment to generate the accelerated surface runoff and inundation hazard maps applying weighted overlay operation. The final map showed that about 35.07 km2 (8%) and approximately 56.55 km2 (14%) of the study area are identified as very high- and highly prone to accelerated surface runoff, respectively. Correspondingly, around 79.89 km2 (18%) and 122.02 km2 (∼28%) belong to the very high and high-water accumulation potential areas, respectively. In summary, it is estimated that about 36% of the water accumulation potential area falls in the densely populated urbanized zones, compared to the accelerated runoff potential detected in undeveloped areas. This implies that there is a higher risk of flooding in the study area than accelerated runoff. However, since the runoff effect occurred mostly in agricultural areas, there is a need for a detailed investigation of this on crop production. Although this study applied a very simple approach, it yielded a high accuracy map (87.5%) which provides useful information for decision-makers to stimulate effective land use planning, alleviate flood occurrence, and reduce soil degradation.