Articles & Case Studies

Flood management study on the Orange River

Posted: Friday 16th May 2014

HR Wallingford has teamed up with Johannesburg-based Fourth Element Consulting to offer sustainable environmental solutions to the rapidly developing economies in southern Africa. The two organisations are now collaborating on a project to investigate flood management solutions for the Orange River in South Africa.

Fourth Element Consulting has been engaged by ILISO Consulting to undertake the hydraulic modelling of the Orange River in the Northern Cape, South Africa. ILISO has been appointed by the Northern Cape Department of Agriculture, Land Reform and Rural Development to provide flood management assistance in the Lower Orange River. The project includes the hydraulic modelling of over 350 km of river, covering the vineyards and wheat fields from Boegoeberg Dam (near Groblershoop) to Onseepkans. Over R1 billion has been allocated to the rehabilitation works.

A two-dimensional (2D) model is being developed and is probably the largest 2D simulation of a river system undertaken in South Africa. “The Orange River is a highly braided system with important agricultural lands utilising all available land. 2D modelling better represents the effects of the flood levees that protect agricultural lands from frequent flooding”, says Stuart Dunsmore, managing director of Fourth Element. Many of these levees suffered damage in the floods of 2011 and the Department is reviewing both the design and level of protection appropriate for the levees.

Fourth Element has employed the expertise of HR Wallingford to provide technical advice to the project team. David Ramsbottom is an international specialist in flood management and irrigation systems. “While the irrigation systems along the Orange River appear well planned and highly effective, there are some notable differences in the design of the flood levees compared to international standards”, says Ramsbottom. “The Department is already addressing some of the present shortcomings, but it will be important to use the model to assess cause and effect of the design heights of the levees. Levees that are too high will increase the risk of flooding elsewhere with potentially serious consequences”.

Already over 800 km of flood levees have been identified and are being incorporated in the hydraulic model. “The 2D model will be a very valuable asset for longer term planning, design and even disaster management for communities along the river”, says Dunsmore. “The data sets are enormous and each model will take a number of days to run. However, preliminary runs are already showing the potential of the models”, he says.

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August 2021

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