Die identifisering van ontwikkelingsensitiewe areas teen berghellings : Stellenbosch- en Hottentotshollandberge

James, Arthur Jeffree (2001-03)

Thesis (MA)--Stellenbosch University, 2001.

Thesis

ENGLISH ABSTRACT: Agricultural and forestry development as well as the erection of buildings and other structures against steep mountain slopes is currently a substantial problem in the Boland. Such developments can be detrimental because of aesthetic considerations and the environmental damage that can arise therefrom. In this regard, environmental damage specifically includes the destruction of fynbos and soil erosion, the latter also having a negative impact on agriculture. This study has attempted to identify areas sensitive to development, and from the resulting findings to develop a set of guidelines for possible future development along the mountain slopes of the Boland. The study area includes only a part of the Boland mountains, namely the Stellenbosch and Hottentotsholland mountains, but can serve as a pilot area for other regions in the Boland possibly plagued by the same problems. Analyses were primarily undertaken by means of GIS software such as inter alia Unix Arc/Info and ArcView 3.1. Various remote sensing techniques were also used to interpret and analyse Landsat TM satellite imagery. For these analyses the image processing program Idrisi for Windows was mainly used. Because the study concentrates on agricultural development, certain criteria such as the erodibility of soil types and the gradient had to be taken into account in the identification of sensitive areas. With regard to gradient data, the use of a "Digital elevation model" (OEM) was of cardinal importance. Other types of development (buildings and structures, as well as forestry) were also analysed to establish firstly where these developments occur; and secondly whether they occur in sensitive areas as far as the height and gradient of slopes are concerned. Because of the subjectivity that exists with regard to the visual impact of these developments, it is difficult to determine what developments on high mountain slopes are aesthetically acceptable and what are not. According to the Act on Agriculture no. 9238 of 1984, slopes with a greater than 20% gradient may not be ploughed without special permission. Against this background the most important result of the analyses undertaken in this study, was the identification of agricultural areas sensitive to erosion. Finally, guidelines are suggested that can be applied to possible future developments on the mountain slopes of the Boland.

AFRIKAANSE OPSOMMING: Landbou- en bosbou-ontwikkeling sowel as die oprigting van geboue en ander strukture teen steil berghellings is tans 'n wesenlike probleem in die Boland. Sulke ontwikkelings kan nadelig wees weens estetiese oorwegings en omgewingskade wat hieruit kan voortspruit. In hierdie verband verwys omgewingskade spesifiek na fynbosvernietiging en gronderosie. Gronderosie het natuurlik ook 'n negatiewe impak op die landbou. Daar is in hierdie studie gepoog om ontwikkelingsensitiewe areas te identifiseer, en vanuit bevindinge 'n stel riglyne te ontwikkel vir moontlike toekomstige ontwikkeling teen die berghellings in die Boland. Die studiegebied sluit slegs 'n gedeelte van die Bolandse berge in, naamlik die Stellenbosch- en Hottentotshollandberge, maar kan dien as loodsgebied vir ander streke in die Boland wat moontlik dieselfde probleme ondervind. Analises is hoofsaaklik gedoen deur middel van geografiese inligtingstelsels- (GIS-) programmatuur soos onder andere Unix Arc/Info en ArcView 3.1. Afstandswaarnemingstegnieke is ook aangewend om Landsat TM- satellietbeelde te interpreteer en te analiseer. Vir hierdie analises is hoofsaaklik van die beeldverwerkingsprogram Idrisi for Windows gebruik gemaak. Omdat die studie op landbou-ontwikkeling konsentreer, moes sekere kriteria soos die erodeerbaarheid van grondtipes en gradiënt in ag geneem word in die identifisering van sensitiewe areas. Wat gradiëntdata betref, was die gebruik van 'n "Digital elevation model" (OEM) van kardinale belang. Ander tipes ontwikkelings (geboue en strukture, asook bosbou) is ook ontleed om eerstens te bepaal waar hierdie ontwikkelings voorkom; en tweedens of hierdie ontwikkelings in sensitiewe areas wat hoogte en gradiënt betref, voorkom. Weens die subjektiwiteit wat rondom die visuele impak van hierdie ontwikkelings bestaan, is dit moeilik om te bepaal watter ontwikkelings teen hoë berghellings esteties aanvaarbaar is en watter nie. Volgens die Wet op Landbou no. 9238 van 1984 mag hellings met 'n gradiënt steiler as 20% nie sonder spesiale toestemming geploeg word nie. Teen die agtergrond hiervan is die belangrikste resultaat van analises in hierdie studie, die identifisering van erosiesensitiewe landbou-areas. Riglyne wat toegepas kan word op moontlike toekomstige ontwikkelings teen die berghellings in die Boland, word laastens voorgestel.

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