ABSTRACT

Soil erosion is one of the geo-environmental hazards that is occuring the world over. In this work, interest was given to gully erosion type which is occurring in the study site, Umudike stream valley. The effect of this gully is evident in the cutting off of paths leading to the stream, reduction in the size of farmlands among other ill effects. This study investigated the underlying causes and effects of gully erosion in the area, and two approaches which are the regression analysis of rainfall data of Umudike geographical location and a laboratory analysis of the soil physical properties conducted on the soil samples collected from the erosion site were adopted to find the cause. Fig 4. Shows results from the finding that rainfall pattern over the 35 years data gotten from the Agro-met Unit of NRCRI is gradually increasing in all this years as seen in the regression graph plotted, thereby contributing enormously in the gully nightmare. Also, the PCA tool employed to deduce which soil physical property has contributed more in influencing and propelling erosion, showed that CDV of total porosity, aggregate stability, hydraulic conductivity and PSD in calgon for water, PSD in water for clay and PSD in water for sand are the main principal component variables out of the nine component variables that influence erosion. Fig 5.illustrates the scree plot graph of the fraction of the total variance in the soil dataset. In all this properties, a peculiar characteristic of them from the study is that they are most prone to erosion and one of a gully nature occurring in the study site due to their weakness in resisting rainfall impact as they are easily dispersed and infiltration highly reduced leading to run off and encourages gully erosion. Thus, rainfall and poor soil physical properties are the underlying cause of gully erosion in Umudike-stream valley. However, certain steps can be adopted in an effort to combat the gully menace such as planting of bamboos and vegetative trees, creation of drainage to channel the rainfall water off the slope etc.