ABSTRACT

The study and design of soil erosion control structure for Nsulu erosion site at Isiala Ngwa North Local Government Area of Abia State was carried out, which includes particle size analysis, moisture content, bulk density, porosity, field permeability etc. The results of the structural class (% sand, % silt, % clay), saturated hydraulic conductivity , moisture content, bulk density and porosity of the soils from the selected locations at the gully head, middle and tail were presented Table 4.1. The moisture content obtained from the soil samples collected from the three experimental sites locations show that moisture content for soils ranges from 18.0 % to 21.4 % with the average moisture content of 19.5 as at the time of the study. The average value of the soil bulk density for the gully effected area was 1.27 g/cm3while the average value of the porosity obtained for the experimental site was 46.2 g/cm3. The saturation hydraulic conductivity of the experimental sites ranges from 4.12 X iO to 5.85 x iO indicating high value of hydraulic conductivity. It is observed that soils with high K value has the low clay content, and soil with low K value has the high clay content. This is in agreement with the work of Emeka-Chris (2010) that states that soils with higher K values should have lower clay content and are more prone to erosion. Low clay % content results in lower binding forces and poor cohesion. A trapezoidal channel was designed carrying 3.3m3/s with bottom width of 0.93m, depth of l.0m and side slope of 2:1 respectively to control the erosion by conveying the runoff to the nearest rural river that serves as outlet discharge point.