Computing the sediment and ensuing its erosive activities using HEC-RAS to surmise the flooding in Kulfo River in Southern Ethiopia

Abstract

Purpose

The change in sediment transport phenomenon and morphological characteristics of Kulfo River in the southern part of Ethiopia is estimated using one-dimensional hydraulic modelling. The purpose of this study is to predict erosion and sedimentation using hydrological engineering center-river analysis system (HEC-RAS) model.

Design/methodology/approach

Geometrical survey data of 2005 and 2019 were used to assess the impact of flood depth with 100 years of return per period on the morphology of the river. The bed and bank materials at selected sites of the river were sampled to estimate the grain size using manning roughness coefficient. Discharge and suspended sediment concentration were sampled thrice per day for a stretch of three months to develop a rating curve.

Findings

HEC-RAS model indicates that flood depth with 100 years return period had a significant inundated area during 2019 in comparison to 2005 demonstrating a temporary change in the morphology of the river. Acker and White method in HEC-RAS was used extensively to calculate the sediment load and subsequently calibrated. In the upper reach of the study area, there was aggradation and degradation, whereas the only degradation was noted in the middle to the downstream reach of the channel. Seasonal flood during peak flow due to a rise in bed level is most prevalent during the aggradation period.

Originality/value

Comparison of a flood depth inundating the catchment and sediment deposition has been intricately analyzed by using HEC-RAS model.

Citation

Damte, F., G_Mariam, B., Ayana, M.T., Lohani, T.K., Dhiman, G. and Shabaz, M. (2021), "Computing the sediment and ensuing its erosive activities using HEC-RAS to surmise the flooding in Kulfo River in Southern Ethiopia", World Journal of Engineering, Vol. 18 No. 6, pp. 948-955. https://doi.org/10.1108/WJE-01-2021-0002