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dc.contributor.advisorLe Roux, J. S.
dc.contributor.advisorBarker, C.
dc.contributor.authorVrahimis, Sheila
dc.date.accessioned2018-06-07T16:54:57Z
dc.date.available2018-06-07T16:54:57Z
dc.date.issued1999-12
dc.identifier.urihttp://hdl.handle.net/11660/8389
dc.description.abstractEnglish: An investigation of the literature on slopes revealed that some researchers found a relationship between rock fragment size and slope angle on debris slopes whilst others find no such relationship at all. This project endeavored to empirically test whether such a relationship exists. The literature reveals confusion regarding the concept of debris slopes. It was found that the terms scree slope, debris slope and boulder- controlled slope were used interchangeably. Research findings of scree slopes were used for debris slopes and vice versa. The debris slopes identified for this project conform to the requirements as stated by Young (1972) and comprises a regolith covered slope occurring beneath a free face on which boulders display an upwards increasing tendency in size. Four hills in the southern Free State (semi-arid climate) were selected and on these ten profiles were surveyed. The literature reveals purposive sampling as opposed to random sampling of hills for study and this project is no exception. The choice of profiles were led by the requirements proposed by Young (1972) as well as including only hills with a debris slope of the Beaufort series overlain by a dolerite caprock. Control of the latter variable successfully allowed for isolating the origin of debris on the debris slope (as these comprised dolerite from the caprock). Research that did not control this variable ran into trouble isolating the exact origin of debris on the slopes which impacted on results and conclusions. The profiles were surveyed using an Abney level and the profile- meter of Le Roux (1980) which is 2m in length. Profiles were surveyed down the true slope (perpendicular to the contours) and a line sample of all debris 30 mm and larger on the profile were included for study. The debris sample is therefore representative of a particular measurement of slope. Differences amongst researchers exist regarding the downs lope boundary of a debris slope. This also impacts on research findings. In this project the downslope boundary was determined using the two variables of slope angle and percentage debris cover as opposed to only using slope angle (and this value was in many cases arbitrarily determined) as revealed in previous research. Thus for this study the debris slope comprises the part of slopes commencing at the foot of the free face with the lower boundary based on a low slope angle (≤ 5°) combined with a low percentage debris cover (≤ 2% > 30mm diameter). In previous research only one dimension of debris was measured as opposed to measurement of all three dimensions as in this project. A variety of indicators for debris size were calculated and correlated with slope angle and transformations of angle. These indicators were also correlated with distance from the bottom of the free face. Small, but statistically significant correlations were obtained. Comparison of correlations obtained for the different indicators indicated trends in the data which impacted on the research findings. Calculation of the indicators also allowed for controlling variation in calculating correlations. This demonstrated why many researchers were led to deduce a causal relationship between slope angle and debris size. Manipulation of data which included the isolation of outliers as well as variations in measuring length indicated increases in values obtained for correlations. The latter indicated the importance of the size of the measuring length in obtaining results. This revealed a possible reason why researchers using a measuring length of >2m found a causal relationship between slope angle and debris size. Measurement of all three dimensions of the debris allowed for an investigation into the shape of particles. This demonstrated the importance of particle shape on sorting as well as in the processes operating on slopes and hence the effect of particle shape on slope development. Slope angle frequency distributions were examined and it revealed that debris slopes in the 5° to 10° and 15° to 20° categories could be considered stable for the sampling space. Slopes above 350 are rare and therefore can be regarded as unstable by using ergodic reasoning. From the research it was concluded that debris slopes in this area are mainly structurally controlled but that slope angle and shape comprise a complex function of structure and process over time. With a relatively stable base level slope development is the result of parallel retreat.en_ZA
dc.description.abstractAfrikaans: In die literatuur bevind sommige navorsers' n verband tussen die grootte van puin en die hellingshoek van hange. Andere bevind geen verband nie. Hierdie studie is aangepak om empiries vas te stelof daar 'n verband tussen hellingshoek en puingrootte op puinhange bestaan. Uit die literatuurstudie blyk dit dat daar verwarring rondom die konsep van puinhange bestaan. Sodoende gebruik sommige navorsers die terme talushange, "scree" hange, rotsbeheerde ("boulder controlled") hange en puinhange as sinonieme. Navorsing wat op puinhange toegespits is, word as bewyse vir talus- en "scree" hange gebruik en anders om. Die puinhange in hierdie studie voldoen aan die vereistes soos deur Young (1972) gestel naamlik 'n regolietbedekte hang benede 'n vryhang waarop puin met 'n afwaartse neiging in puingrootte voorkom. Vier inselberge is in die suidelike Vrystaat gekies en op hierdie heuwels is tien profiele opgemeet. Net soos in ander navorsing is die metode nie ewekansig nie en is die keuse in hierdie geval gelei deur die vereistes wat aan 'n puinhang deur Young (1972) gestel is sowel as dat die heuwels uit' n dolerietdekrots met' n puinhang van Beaufort gesteentes bestaan. Laasgenoemde vereiste het tot gevolg dat die dolerietpuin op die puinhang onbelemmerd waargeneem kon word. Navorsers wat nie hierdie faktor beheer het nie het probleme om die herkoms van 'n puinbrokstuk vas te stel en dit hou ernstige gevolge vir die resultate en afleidings in. Die profiele is met die profielmeter van Le Roux wat 2m in lengte is en 'n Abney-waterpas langs die ware helling (loodreg op die kontoere) gemeet. 'n Lynmonster van die puin is teen die ware helling van die puinhang geneem en is dus verteenwoordigend van wat by 'n spesifieke meeteenheid op die helling voorkom. Alle puin van 30mm en groter wat aan die profiellyn geraak het, is in die puinmonster ingesluit. Die onderste grens van die puinhang is op grond van twee parameters, naamlik hellingshoek en voorkoms van puin vasgestel. Sodoende bepaal 'n lae hellingshoek (≤ 5°) gekoppel aan 'n lae persentasie puinbedekking (≤2% > 30mm gemiddelde deursnee) die onderste grens, terwyl die boonste grens deur die vryhang vasgestel word. Hierdie metode verskil van dié van ander navorsers wat die onderste grens gewoonlik net op grond van hellingshoek (en hierdie hoekwaarde verskilook onderling tussen navorsers) vasstel. Uit die literatuur blyk dit dat navorsers slegs een dimensie van die puin gemeet het. In hierdie studie is al drie dimensies van die puin op die lynmonster gemeet. Verskeie indikatore van puingrootte is vir die data bereken en korrelasies is met hellingshoek en transformasies daarvan, sowel as afstand vanaf die vryhang bereken. Die korrelasies het klein, maar beduidende waardes gelewer. Onderlinge vergelyking van die korrelasies met die aanduiders van puingrootte het tendense in die data aangetoon wat die afleidings beïnvloed het. Die indikatore het bygedra dat die variasie van die puin tydens die berekening van korrelasies beheer kon word wat belangrike implikasies vir die afleidings ingehou het. Sodoende kon aangetoon word waarom sommige navorsers daartoe gelei was om 'n kousale verwantskap tussen hellingshoek en puingrootte af te lei. Manipulasies van die data is uitgevoer wat onder andere die verlenging van meeteenhede en die uitskakeling van uitskieters insluit. Telkens het die korrelasies verhoog. Dit het die belangrikheid van die lengtes van meeteenhede op die gevolglike afleidings aangetoon en gedemonstreer waarom navorsers wat slegs van lang meeteenhede gebruik gemaak het 'n kousale verband tussen hellingshoek en puingrootte bevind het. Weens die meting van al drie dimensies van die puin kon 'n ondersoek na die vorm van die puin geloods word. Dit het die belangrikheid van vorm op die sortering van die puin aangetoon asook die rol daarvan in die prosesse op die hange en dus die effek daarvan op hangontwikkeling benadruk. Die verspreiding van hellingshoeke is ondersoek. Daar is bevind dat stabiele hellings vir die puinhange in die steekproefruimte in die 5° tot 10° en 15° tot 20° kategorieë val. Hellings bo 35° is skaars en kan deur middel van ergodiese beredenering as onstabiel gesien word. Die onderhawige studie bevind dat die puinhange in hierdie gebied hoofsaaklik struktuurbeheerd is, maar dat die hellingshoek en vorm van die hange 'n komplekse funksie van struktuur en proses oor tyd is. Met 'n basisvlak wat relatief stabiel is, vind hangontwikkeling, nadat 'n ekwilibrium helling vir die bodemgesteente van die puinhang ontwikkel is, deur middel van ewewydige terugwyking plaas.en_ZA
dc.language.isoafen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectSlopes (Physical geography)en_ZA
dc.subjectGeomorphology -- Free Stateen_ZA
dc.subjectDissertation (M.A. (Geography))--University of the Free State, 1999en_ZA
dc.titleHang- en puinmorfometrie van heuwels met 'n dolerietdekrots in die semi-ariede Suidelike Vrystaaten_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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