Design of an Open Channel for Flood and Gully Erosion Control: A Case Study of Amakohia-Uratta in Imo State, Nigeria

Flooding and gully erosion constitute a major problem associated with urbanization in the underlying watershed of an area. In this study, a trapezoidal channel hydraulic system was designed for flood and erosion control in Amakohia-Uratta, Owerri North, Imo state, Nigeria. A topographical survey of the study area was done. The result shows that the maximum elevation is 81.03 m, the minimum elevation is 78.21 m, the bed slope of the area is 0.02%, the area of the watershed is 1.061ha, and the maximum length of flow is 140m. Also, the results from the hydrological analysis using the rational method indicated that the rainfall intensity of 10 years duration was 105.3 mm/h with a peak discharge Qp of 0.17 m3/s, causing the flood and erosion, while the channel design capacity (discharge) Qd is 0.17 m3/s, calculated using trial and error methods. Finally, design parameters for the trapezoidal open channel were calculated. The result indicated that the channel width is 0.3 m, the design depth is 0.5 m, the freeboard is 0.1m, the total channel depth is 0.6m, the top width of the channel is 2.1 m and the side slope is 1.5:1. In all the design is appropriate to capture, carry and discharge the peak runoff to Nworie River a natural outlet.