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University of Cape Town (1998)

Soil erosion and land degradation in the Swartland and Sandveld, Western Cape province, South Africa : a re-evaluation

Morel, Anneke

Titre : Soil erosion and land degradation in the Swartland and Sandveld, Western Cape province, South Africa : a re-evaluation

Auteur : Morel, Anneke

Université de soutenance : University of Cape Town.

Grade : Master of Arts in Environmental and Geographical Science 1998

Résumé
The Swartland and Sandveld are situated in the Western Cape province (political limits) in what is also known as the southwestern Cape region . This area falls within the winter rainfall (or Mediterranean) region of South Africa and has a sharply defined seasonal climate. Vegetation in the region is unique. The soils in the Swartland and Sandveld vary greatly over short distances, making this area vulnerable to varying erosion rates. Landuse in the Swartland and Sandveld is mainly agricultural. Soil erosion is driven by the force of wind and or water. Sheet flow is what is considered as unconstrained water erosion together with rainsplash, while piping, rill and gully erosion are all forms of constrained water erosion. Erosivity and erodibility are both important factors in determining the vulnerability of an area to soil erosion. By their understanding of the factors involved in the course of degradation, researchers can determine the most effective conservation policies for a region. Of course, the influence of humans on the land should never be under-estimated and should be seen as a potent determinant of the erosion potential. The use of remote sensing and G.I.S. are essential in the development of erosion maps, and to assess possible changes that over time in the erosional situation in a region. As an analytical and data storage tool, these techniques are very useful, even essential. The total decrease in gully erosion from 1938 to 1989 in the Swartland amounts to 85% compared to the gully erosion in 1938. In the Sandveld wind erosion decreased with 17% from 1928 to 1986. Soil conservation in South Africa has come a long since the 1930’s and much of the experience and the lessons gained in the last six of seven decades have been incorporated in the countries new conservation Act. It has been concluded that the slowing down of the denudation process in the region, coinciding with effective new conservation strategies, are the The Swartland and Sandveld are situated in the Western Cape province (political limits) in what is also known as the southwestern Cape region. This area falls within the winter rainfall (or Mediterranean) region of South Africa and has a sharply defined seasonal climate. Vegetation in the region is unique. The soils in the Swartland and Sandveld vary greatly over short distances, making this area vulnerable to varying erosion rates. Landuse in the Swartland and Sandveld is mainly agricultural. Soil erosion is driven by the force of wind and or water. Sheet flow is what is considered as unconstrained water erosion together with rainsplash, while piping, rill and gully erosion are all forms of constrained water erosion. Erosivity and erodibility are both important factors in determining the vulnerability of an area to soil erosion. By their understanding of the factors involved in the course of degradation, researchers can determine the most effective conservation policies for a region. Of course, the influence of humans on the land should never be under-estimated and should be seen as a potent determinant of the erosion potential. The use of remote sensing and G.I.S. are essential in the development of erosion maps, and to assess possible changes that over time in the erosional situation in a region. As an analytical and data storage tool, these techniques are very useful, even essential. The total decrease in gully erosion from 1938 to 1989 in the Swartland amounts to 85% compared to the gully erosion in 1938. In the Sandveld wind erosion decreased with 17% from 1928 to 1986. Soil conservation in South Africa has come a long since the 1930’s and much of the experience and the lessons gained in the last six of seven decades have been incorporated in the countries new conservation Act. It has been concluded that the slowing down of the denudation process in the region, coinciding with effective new conservation strategies, are the University of Cape Town principal reasons for the results obtained in this research project. It must be noted however that without the intervention of the conservation efforts in the Swartland and Sandveld, the remarkable improvement in the water erosion situation (85%) would not have been obtained. The overall improvement (17%) in the Sandveld lags that in the Swartland and even shows a slight deterioration of the wind erosion situation found in 1974. There are therefor grounds for caution, since wind erosion is still very much relevant and not fully contained in the Sandveld. Further research into this situation would indeed be beneficial.

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