The use of erosion models to predict the influence of land use changes on urban impoundments.

Adriaan Gilau

Friday 3 july 2015

12:33 - 12:36h at South America (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) Basin-wide sediment management, Poster pitches

Parallel session: Poster pitches: 15J. Sediment - Basin & Environment - Wetland

Impoundments in urban areas of South Africa, either natural or artificial, are popular recreational attractions that add to the quality of life, increase property value and are increasingly built as focal points for commercial developments. More regularly such impoundments acts as receptacles for polluted runoff, resulting in water quality problems and ultimately reduce the aesthetic value and undermine their recreational value and function as originally envisaged (Freeman et al, 2000). The impact of soil loss from urban erosion processes is a major problem confronting decision makers on a national and local level due to the impact on local resources (Le Roux et al., 2007). One such resource is the Boksburg Lake in the Eastern Service Delivery Region of the Ekurhuleni Metropolitan Municipality of the Gauteng Province, South Africa. The purpose of the study was to quantify what impact soil erosion processes, as a result of changes in land-use, had on the urban impoundment. There is a close relationship between how land is managed and the impact erosion may have on in-stream health. Increased erosion as a result of catchment changes increases the loads of phosphorus introduced into streams (Croke, 2002) and subsequently increases the occurrence of eutrophication. Resent research has discovered that existing stores of sediment, as a result of previous erosion (mid–to-long term), are responsible for the delivery of additional phosphorus to waterways and reservoirs (Croke, 2002). The management of sediment levels combined with reduced catchment phosphorus load is viewed as the most viable option in eutrophication abatement. The study used a modified approach of the Universal Soil Loss Equation and the Soil Loss Estimation Model for Southern Africa, suited for urban conditions. These approaches were adopted for South African conditions. Proposed management practices for the reduction of the erosion are presented.

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