Effects of Rainfall Intensity and Slope Angle on Splash Erosion in Makurdi, Benue State

Abstract

Soil erosion is a critical global environmental problem, especially in the developing countries including Nigeria. In the humid and sub-humid tropics, splash erosion resulting from intense rainfall and slope degree pose severe land degradation problems. The objective of this study is to assess the effects of some rainfall parameters and slope on directional components of splash erosion in the Makurdi area of Benue State. Data were collected on rainfall amount and duration in an experimental station in Benue State University, Makurdi for a period of one rainy season in 2007. Sediment collectors attached to soil trays placed at angles 5, 15, 25 and 35 degrees were used to collect the amount of splash at the end of every rain day. The soils were oven dried and measured. The amount of soil splashed was statistically analyzed after weighing to verify the slope effects on splash. The results showed that slope has a significant effect on the downslope and upslope components of the splash. Downslope component increased with slope while the upslope component decreased, reflecting variations of raindrop impacting forces and ponding depth with slope. Total splash increased with slope angle to a peak at 150 and then decreased with increasing angle. Factors of slope angle, rainfall amount, and intensity, and total kinetic energy were regressed against directional components of splash. The result showed that 70% of variations in the downslope splash is explained by these factors. Further research is recommended on slope orientations at different wind directions and rate of rain capture on erodibility.

KEYWORDS: Splash, erodibility, slope, erosivity, Modeling.