Assessment of gully erosion from coastal plain sands of Ogburu, Ilaro, Ogun State

Abstract

The field measurements were used to calculate the discharge using hydraulic equations. The calculated discharges with limited hydraulic and hydrologic data were then used to establish an erosion rate equation i.e. E = 0.025 (1.022Q) 15/8L3/8 So3/2 (Kg/m2/hr) which was used to estimate erosion rate. Three established functional relationships were found to be highly correlated, these are; discharge as a function of erosion rate Q = f(E); shear stress as a function of discharge _ = f(Q) and shear stress as a function of erosion rate _ = f( E). The simple linear regression model results are Q = 28.63 + 17. 38E. _ = 19.47 + 3.19Q and _ = 120.24 + 22.45E with correlation coefficients, r = 0.86, 0.89 and 0.93 and coefficient of determination, r2 = 74%, 79% and 86% respectfully, the very high coefficient of correlation (r) and determination (r2) is enough justification to conclude that the derived equations can be used to estimate the magnitude of erosion rate or extent and its future severity can be predicted from hydraulic parameters measured on site. The established relationships from limited hydraulic parameters can be used to assess the gully erosion from the site. Keywords: Erosion Rate E (Kg/m2/hr), Shear stress _(N/m2), Mannings Roughness Coefficient (n). [Global Jnl Environ Sci Vol.1(1) 2002: 27-34]