Browsing by Author "Isa B. Salami"

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    Flood Susceptibility Mapping in Asa Local Government Area, Kwara State, using Remote Sensing and GIS Approach
    (1Department of Geography and Environmental Management, Faculty of Social Science, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria 2Department of Surveying and Geoinformatics, Faculty of Environmental Science, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria, 2022) Isa B. Salami; Falilat O. Lawal; Mohammed O. Idrees; Okochi M. Ifechukwu; Ayo Babalola; Dahir M. Omar; Azeez K. Alade
    Abstract: The increasing incidences of flood events in recent times have necessitated the need to come up with an early warning information for flood risk preparedness and reduction. The study aimed at mapping flood susceptibility in Asa Local Government Area, Kwara State, using Geographic Information System (GIS) based multi criteria evaluation approach. The data required for the study include: rainfall amount, soil texture, digital elevation model, distance from stream (euclidean distance) and land use land cover of the study area. Using Analytic Hierarchical Process, flood criteria weights were calculated for the different variables according to their influence on flooding and overlay analysis was employed in analysing the data for the study. The result of the study show there is spatial variation in the level of susceptibility to flood risks in the study area. Thus, the low-risk area covers 16.1% (~222.24 km2 ), moderate class 28.8% (~398.08 km2 ), high risk zone occupies 39.5% (~408.70 km2 ) while the very high-risk zone takes up 25.6% (~354.15 km2 ) of the area coverage of the study area. Furthermore, the accuracy assessment produced area under the curve (AUC) value of 0.795 (~80%). From the study, it was also discovered that Owode, parts of Afon, Bode, Onikangu, Abule-Alagbede fall within the very high and high-risk flood zones. The map could be a useful tool to decision makers in Asa local government for effective flood management plans.
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    Modelling Flood Hazards Impacted by Ungauged River in Urbanised Area Using HEC-RAS and GIS
    (Department of Surveying and Geoinformatics, Faculty of Environmental Sciences, University of Ilorin, Nigeria. 2Department of Surveying and Geoinformatics, Faculty of Environmental Sciences, University of Abuja, Nigeria., 2023) Isa B. Salami; Abdulganiyu Yusuf; Romoke Ojo1; Mohammed O. Idrees; Abdul-Lateef Balogun; Ojogbane S. Sani
    ABSTRACT: Ilorin City is located downstream of Asa, Oyun and Awun River Basins. The Asa River is a major river that traverses the city and divides the metropolitan area into east and west, almost equally. The river often overflows its banks to inundate adjacent communities, influencing severe economic damage and impact on human lives. However, efforts to mitigate this have majorly been focused on dredging the Asa River channel which has not solved the problem. For an accurate spatial and temporal understanding of the risks of floods and their potential hazards, it is important to estimate floods using river hydrology. The objective of this study is to model steady flow of the rivers using flow data and to map flood-prone areas in Ilorin using HEC-RAS integrated with GIS. Using the HEC-GeoRAS extension in the GIS environment, the geometric data of the rivers were obtained from the 30 m resolution digital elevation model (DEM) and input into HEC-RAS applying Manning Co-efficient values of 0.04, 0.045, and 0.04. For each river, flow data (Q) was given as the upstream boundary condition while a normal depth of 0.001 was assigned for the downstream condition to model a steady flow and inundation extents. The result of the HEC-RAS model has shown the flood-prone areas along the river channels delineated. The floodplain map produced reveals the spatial distribution and extent of the high flood-risk areas in the Ilorin metropolis. The total flooded area covers approximately 60.95 km2 (18%) majorly along the river channels. This study has demonstrated that integration of hydraulic modelling using HEC-RAS and GIS process is capable of producing an inundation flood map with good accuracy that will aid in suggesting effective measures to mitigate the impact of flooding.