Assessment and Mapping of Gully Erosion Geo-hazards in Agulu – Nanka, Southeastern Nigeria: An Integrated Geotechnical and GIS Approach
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The gully erosion is the most serious environmental problem in Agulu-Nanka, Southeastern Nigeria. Present study focused on characterization of geo-environmental factor in the gully affected areas to prevent future problems. The study investigates geotechnical analysis and catchment management of gully erosion in Agulu - Nanka, Anambra State, Nigeria. The major objectives were: to provide geotechnical parameters and data (permeability, liquidity, plasticity, consistency, moisture content and compaction) of the soils available in Agulu Nanka, Anambra State. The method of data collection employed was through field work which involves the use of GPS to capture the coordinates of the gully sites and tape rule to measure the width, depth, and length of the gullies. GIS techniques were used in data analysis. A total of 14 gully sites were coordinated and mapped, the result reveals the gully erosion were dispersed with areas of Nanka/Oko having the highest concentration of gullies. The generation of gully characteristic map reveals that the gullies vary from area to area in relation to their lithology. The characteristic map (in meters) was classified into three parameters with 2.00-6.06 as Low, 6.06-8.89 as Medium, and 8.89-13.77 as High. The gullies with the highest depths were within the coordinates of N6220.9364, E7458.5948; N6228.6836, E7459.4048; N6311.6208, E74333.6612 with 52.96m, 47.32m and 45.18m respectively. The length of the gullies at the concentrated region stretched as far as 4.37km while the gully with the largest width covered a large space of 397.20m. The result indicate the need for incorporation of gully vulnerability, the areas require dire attention to arrest the menace of the erosion threats.
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