Analysis of Gully Erosion Dynamics in Federal College of Education (Technical), Gombe, Gombe State, Nigeria

Abstract

The paper examines dynamics of gully erosion sites at Federal College of Education (Technical), Gombe, Gombe State, Nigeria. The specific objectives are: to identify and map out areas affected by gully, examine factors responsible for gully erosion, calculate areas affected by gully, assess effects of the sinuosity of the gullies channel on the morphologies of the gully in the area. The study used primary source of data which includes field observations and measurement of depth, width, depth and length of the gully and sinuosity of the channel. The field survey was conducted to give an overview of the physical condition of the study area, including topography, vegetation and land use type. GPS points of gully sites were also taken. Land-use/land-cover types at five periods were extracted from Google earth, Landsat-TM, and ETM+. Slope and elevation information were also obtained from digital elevation model sourced from Africover portal of FAO website to determine the elevation of the zone. The study used Arc GIS software for the analysis. The findings of the study show that three major gully sites identified are Site A (Demonstration Secondary school), which covers an area of 13498.21 sqm (58.37%), gully site B (behind the Female Hostel) which covers an area of 3536.95sqm (15.30%) while gully site C behind (GOFCECON building) which accounted for 6088.58sqm (26.33%). Types of landuse/Landcover changes found in the area include plantation/trees, shrubs/grassland, build up areas, open space and gully sites. There was a significant decrease in plantation/trees and shrubs/grassland over the years from 49.02% in 2014 to 40.41% in 2018 with an increase in gully size from 0.68% in 2014 to 0.91% in 2018. The sinuosity index is 1.12 which has a significant effect on the expansion of the gully channel in the area. The paper concludes that the factors responsible for the dynamism of gully erosion in the area is a combination of interdependent mechanisms between topography, slope, soil erodibility, landuse/landcover change, which have changed over the years thereby reducing infiltration capacity, increased surface runoff on a steep slope environment. The paper recommends that a specific, scientific and systematic approach which integrates the influence of all factors observed as responsible for gully formation should be employed in the control of gullies in the area.