Modelling soil erosion and sediment transport of the Nqoe River Catchment at 'Muela

Abstract

This study assesses the dynamics of soil loss rates of the Nqoe River Catchment. The assessment is made by numerical modeling of the stream water levels and flow, as well as the suspended and bed-load sediment. Literature states that accelerated soil erosion is a problem in the catchment, resulting in high rates of sedimentation of the ‘Muela Reservoir. This erosion is blamed on the over-stocking of rangelands which leads to overgrazing and development of bare soil cover. As part of literature review, to better understand existing methods for estimation of soil erosion and stream sediment transport, thirteen (13) overland soil erosion equations and forty-two (42) channel erosion and sediment transport equations were coded in over eighteen thousand (18,000) lines of code. Analysis of these models informed the runoff model developed using the Gridded Surface Subsurface Hydrologic Analysis model (GSSHA). The model was calibrated and validated for the Nqoe catchment, and its capability to adequately simulate in this data-sparse geographic region was assessed. It was found that the GSSHA model is robust in its simulations of both stream hydrographs and catchment soil loss. The value of the global gridded satellite rainfall data from the NASA GES DISC proved to be useful and accurate in running the GSSHA model for the data-sparse Nqoe catchment in Lesotho. This data was particularly useful while running land management scenarios for assessment of management activities (reforestation, urbanisation, cropland fallowing and rangeland stocking density) that could best serve to reduce soil erosion in the Nqoe catchment. It was found that reforestation and crop-land fallowing could be some of the most beneficial management strategies for reduction of catchment soil loss.

Date of Award	10 Nov 2018
Original language	English
Awarding Institution	Univerisity of Nottingham
Supervisor	James Andrew Griffiths (Supervisor) & Thorne Colin (Supervisor)