Snow occurs in the High Drakensberg of southern Africa approximately eight times
per annum. Snow cover is frequently captured by Landsat satellite imagery, which
provide data for the monitoring of snow cover in other regions of the world. Together
with a digital elevation model, repetitive snow cover data are used to analyse the
distribution of snow cover in the High Drakensberg study area. The effect that the
regional and local topography, latitude, and climatic conditions have on the spatial
distribution of snow and the function that temperature, wind, altitude, aspect and slope
gradient play in the preservation of snow cover are examined. The results of the
spatial study allow for the identification of sites that support the accumulation of
snow. Specific active and relict geomorphological features were surveyed and
correlated spatially to the contemporary snow cover. Among such features are linear
debris ridges on south-facing valley slopes in the High Drakensberg. These appeared
similar to glacial features found elsewhere in the world and are thus significant in a
long-standing and highly conjectured debate over the validity of possible plateau,
cirque and niche glaciation in the region. Late-lying snow cover favours gently
sloping south- and southeast-facing aspects at altitudes from 3000 m ASL to just
below the highest peaks in the region near 3450 m ASL, above which higher
insolation levels on the flat mountain summits provides unfavourable conditions.
Snow cover immediately adjacent to the Drakensberg escarpment ablates quickly
whilst snow cover at high altitudes in the Lesotho interior experiences better
preservation conditions. Latitude has no obvious impact on the distribution of snow
cover due to the dominant role of topography in the High Drakensberg other than a
limiting of snowfall to regions south of 29°S in late spring. Various synoptic
conditions produce snowfall in the region, with cold fronts associated with midlatitude
cyclones producing the majority of snow cover. A strong correlation exists
between the spatial distribution of snow cover and specific geomorphological
features. Observed linear debris ridges are located on slopes that experience frequent
contemporary snow cover, lending credence for a glacial origin of the ridges during a
period of colder environmental conditions.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/4866 |
| Date | 22 May 2008 |
| Creators | Mulder, Nicholas Andrew Maurits |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 197579620 bytes, application/pdf, application/pdf |
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