Extreme weather events in the Sneeuberg, Karoo, South Africa: a case study of the floods of 9 and 12 February 2011
- Fox, Roddy C, Rowntree, Kate M
- Authors: Fox, Roddy C , Rowntree, Kate M
- Date: 2013
- Language: English
- Type: Article
- Identifier: vital:6672 , http://hdl.handle.net/10962/d1004468
- Description: Two destructive flood events occurred in rapid succession in the semi-arid Sneeuberg Mountains of the Karoo, South Africa in February 2011. The temporal and spatial characteristics of these two extreme events are examined in this paper through analysis of data from an unusually dense, and reliable, network of farm rain gauges. These analyses add to our understanding derived from existing rain gauge information. Comparisons are then made with patterns from a range of modeled products derived from remote sensed information: the Modern-Era Retrospective Analysis for Research and Applications (MERRA), the Tropical Rainfall Measuring Mission (TRMM) and the Global Land Data Assimilation System (GLDAS). We found that the first flood event was widespread and precipitation was related strongly to altitude. The second was highly localised, with no relationship to altitude. Both had very sharply peaked rainfall intensities. These findings are of significance to the studies of flooding and landscape change in the area as such events have become more pronounced over the past 50 yr and it is likely that this trend will accelerate. The modeled patterns are derived largely from remote sensing and we found that they are reliable for drawing out monthly and annual variations but they make noticeable underestimates. They are poor estimates, however, both for the spatial distribution of precipitation, and the short term trends as they struggle to estimate the impact of topography and other local forcing factors. This finding corroborates information derived from other analyses at broader spatial scales using more widely spread, established rain gauge stations. Ten percent of southern Africa has been classified as mountainous and these areas provide much of our water resources so our findings are significant to water managers throughout this and similar mountainous regions.
- Full Text:
- Date Issued: 2013
- Authors: Fox, Roddy C , Rowntree, Kate M
- Date: 2013
- Language: English
- Type: Article
- Identifier: vital:6672 , http://hdl.handle.net/10962/d1004468
- Description: Two destructive flood events occurred in rapid succession in the semi-arid Sneeuberg Mountains of the Karoo, South Africa in February 2011. The temporal and spatial characteristics of these two extreme events are examined in this paper through analysis of data from an unusually dense, and reliable, network of farm rain gauges. These analyses add to our understanding derived from existing rain gauge information. Comparisons are then made with patterns from a range of modeled products derived from remote sensed information: the Modern-Era Retrospective Analysis for Research and Applications (MERRA), the Tropical Rainfall Measuring Mission (TRMM) and the Global Land Data Assimilation System (GLDAS). We found that the first flood event was widespread and precipitation was related strongly to altitude. The second was highly localised, with no relationship to altitude. Both had very sharply peaked rainfall intensities. These findings are of significance to the studies of flooding and landscape change in the area as such events have become more pronounced over the past 50 yr and it is likely that this trend will accelerate. The modeled patterns are derived largely from remote sensing and we found that they are reliable for drawing out monthly and annual variations but they make noticeable underestimates. They are poor estimates, however, both for the spatial distribution of precipitation, and the short term trends as they struggle to estimate the impact of topography and other local forcing factors. This finding corroborates information derived from other analyses at broader spatial scales using more widely spread, established rain gauge stations. Ten percent of southern Africa has been classified as mountainous and these areas provide much of our water resources so our findings are significant to water managers throughout this and similar mountainous regions.
- Full Text:
- Date Issued: 2013
The Evil of sluits : a re-assessment of soil erosion in the Karoo of South Africa as portrayed in century-old sources
- Authors: Rowntree, Kate M
- Date: 2013
- Language: English
- Type: Article
- Identifier: vital:6725 , http://hdl.handle.net/10962/d1006803
- Description: Deep, linear gullies are a common feature of the present landscape of the Karoo of South Africa, where they were known locally in the early twentieth century as ‘sluits’. Recent research has shown that many of these features are now stable and are no longer significant sediment sources, although they are efficient connectors in the landscape. Because most of the gully networks predate the first aerial photographs, little is known in the scientific literature about the timing of their formation. One secondary source, however, throws interesting light on the origin of these features, and the early response by landowners to their rehabilitation. The Agricultural Journal of the Cape of Good Hope at the turn of the Twentieth Century carried a number of articles by farmers and agricultural officers concerning the "evil of sluits". The authors gave accounts of widespread incision of valley bottoms by deep, wide gullies. Many of these gullies had been in existence for some thirty years but apparently had formed within living memory. A number of attempts to prevent further erosion had been put in place at the time of writing. This paper presents a review of land degradation, specifically gully erosion, and rehabilitation recommendations as given by authors writing in this journal. It reflects on the findings in the context of assessing land degradation processes through the local knowledge portrayed in the journal.
- Full Text:
- Date Issued: 2013
- Authors: Rowntree, Kate M
- Date: 2013
- Language: English
- Type: Article
- Identifier: vital:6725 , http://hdl.handle.net/10962/d1006803
- Description: Deep, linear gullies are a common feature of the present landscape of the Karoo of South Africa, where they were known locally in the early twentieth century as ‘sluits’. Recent research has shown that many of these features are now stable and are no longer significant sediment sources, although they are efficient connectors in the landscape. Because most of the gully networks predate the first aerial photographs, little is known in the scientific literature about the timing of their formation. One secondary source, however, throws interesting light on the origin of these features, and the early response by landowners to their rehabilitation. The Agricultural Journal of the Cape of Good Hope at the turn of the Twentieth Century carried a number of articles by farmers and agricultural officers concerning the "evil of sluits". The authors gave accounts of widespread incision of valley bottoms by deep, wide gullies. Many of these gullies had been in existence for some thirty years but apparently had formed within living memory. A number of attempts to prevent further erosion had been put in place at the time of writing. This paper presents a review of land degradation, specifically gully erosion, and rehabilitation recommendations as given by authors writing in this journal. It reflects on the findings in the context of assessing land degradation processes through the local knowledge portrayed in the journal.
- Full Text:
- Date Issued: 2013
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