ASSESSMENT OF LAND SUSCEPTIBILITY TO GULLY EROSION IN ORUMBA NORTH LGA, ANAMBRA STATE, SOUTH EASTERN NIGERIA

Abstract

This study utilizes GIS techniques to determine land susceptibility to gully erosion in Orumba North LGA of Anambra State. Environmental variables of interest in the study include land use, slope (DEM), drainage and soil. The methodology also involves land use classification and reclassification in raster format. Weights are assigned to each raster cell of selected environmental variables according to their level of significance to soil erosion and the combination of individual
variable layer susceptibility weight through overlay technique used Math Raster Calculator in GIS environment was used to determine the actual susceptibility of the land to gully erosion. The result showed that built-up land use which increased from 0.62% in 1986 to 4.43% in 2016, is the most dynamic variable that drives the development of gully erosion in the area. The 1 order streams drain about 60.58% of the study area with a total stream length of 192.65km. Over 40% of land area 0 has a slope higher than 50 and relief of 157m-203m and 203m-255m values which contribute to increase runoff velocity in the study area; thereby catalyzing erosion activities. Loamy sandy soil type covers about 51.47% and has the highest erodibility factor of 0.38. In all, the 'very high 2 susceptibility' land area to gully erosion constitutes 18.78km (5.12%). These are the 'Erosion Hotspot Areas'. The study recommends the provision of green belts infrastructures in the developmental strategies of the city planning authorities. This strategy will mitigate further development and expansion of gullies as the cities expand.