scholarly journals Long-term flood controls on semi-arid river form: evidence from the Sabie and Olifants rivers, eastern South Africa

2015 ◽  
Vol 367 ◽  
pp. 141-146 ◽  
Author(s):  
G. Heritage ◽  
S. Tooth ◽  
N. Entwistle ◽  
D. Milan
Keyword(s):  
South Africa ◽  
Riparian Vegetation ◽  
Optically Stimulated Luminescence ◽  
Primary Control ◽  
Sediment Storage ◽  
Alluvial Sediment ◽  
Extreme Flood ◽  
Bedrock Erosion ◽  
Morphologic Development

Abstract. Rivers in the Kruger National Park, eastern South Africa, are characterised by bedrock-influenced "macrochannels" containing variable alluvial thicknesses and riparian vegetation assemblages. Evidence from the Sabie and Olifants rivers suggests that flows up to moderate floods (<3500 m3 s−1) tend to result in net alluviation, with sediments gradually covering the underlying bedrock. More extreme floods strip alluvium and erode bedrock, effectively exerting the primary control over long-term river morphologic development. On the Olifants River, post-flood aerial LIDAR imagery reveals that the 2012 extreme flood (~14000 m3 s−1) resulted in extensive stripping of stored alluvial sediment, exposing and eroding the underlying weathered bedrock. On the Sabie River, preliminary optically stimulated luminescence ages for remnant alluvium are all less than 1000 years, highlighting typical timescales of sediment storage. Together, these results suggest that while periods of general alluviation occur on these systems, long-term river development results from extreme flood-generated bedrock erosion.

scholarly journals Erosion during extreme flood events dominates Holocene canyon evolution in northeast Iceland

2015 ◽  
Vol 112 (8) ◽  
pp. 2355-2360 ◽  
Author(s):  
Edwin R. C. Baynes ◽  
Mikaël Attal ◽  
Samuel Niedermann ◽  
Linda A. Kirstein ◽  
Andrew J. Dugmore ◽  
...  
Keyword(s):  
Large Scale ◽  
Dominant Role ◽  
Flood Events ◽  
Topographic Analysis ◽  
Exposure Dating ◽  
Extreme Flood ◽  
Bedrock Erosion ◽  
The Impact ◽  
Exposure Ages

Extreme flood events have the potential to cause catastrophic landscape change in short periods of time (100 to 103 h). However, their impacts are rarely considered in studies of long-term landscape evolution (>103 y), because the mechanisms of erosion during such floods are poorly constrained. Here we use topographic analysis and cosmogenic 3He surface exposure dating of fluvially sculpted surfaces to determine the impact of extreme flood events within the Jökulsárgljúfur canyon (northeast Iceland) and to constrain the mechanisms of bedrock erosion during these events. Surface exposure ages allow identification of three periods of intense canyon cutting about 9 ka ago, 5 ka ago, and 2 ka ago during which multiple large knickpoints retreated large distances (>2 km). During these events, a threshold flow depth was exceeded, leading to the toppling and transportation of basalt lava columns. Despite continuing and comparatively large-scale (500 m3/s) discharge of sediment-rich glacial meltwater, there is no evidence for a transition to an abrasion-dominated erosion regime since the last erosive event because the vertical knickpoints have not diffused over time. We provide a model for the evolution of the Jökulsárgljúfur canyon through the reconstruction of the river profile and canyon morphology at different stages over the last 9 ka and highlight the dominant role played by extreme flood events in the shaping of this landscape during the Holocene.

Erosion rates and patterns in a transient landscape, Grand Staircase, southern Utah, USA

Geology ◽  
2019 ◽  
Vol 47 (9) ◽  
pp. 811-814 ◽  
Author(s):  
Kerry E. Riley ◽  
Tammy M. Rittenour ◽  
Joel L. Pederson ◽  
Patrick Belmont
Keyword(s):  
Grand Canyon ◽  
Climatic Forcing ◽  
Sediment Storage ◽  
Erosion Rates ◽  
Base Level ◽  
Rock Types ◽  
Alluvial Sediment ◽  
Dynamic Landscapes ◽  
Cosmogenic 10Be

AbstractCosmogenic 10Be concentrations in alluvial sediment are widely used to infer long-term, catchment-averaged erosion rates based on the assumption that the landscape is in mass-flux steady state. However, many landscapes are out of equilibrium over millennial time scales due to tectonic and climatic forcing. The Grand Staircase of the Colorado Plateau (North America) is a transient landscape, adjusting to base-level fall from the carving of the Grand Canyon, and is characterized by cliff-bench topography caused by differential erosion of lithologic units. The 10Be concentrations from 52 alluvial and colluvial samples, collected in nested fashion from five catchments, produced inferred erosion rates ranging from 20 to >3500 m/m.y. (or mm/k.y.). We attribute this high variance in part to lithologic-controlled steepness and hotspots of erosion related to cliff retreat along the White Cliffs (escarpment near Mt. Carmel Junction, Utah), as well as headward drainage expansion along the uppermost Pink Cliffs (escarpment within Bryce Canyon National Park). Results from the downslope Vermillion Cliffs (near Kanab) indicate lower erosion rates despite similar slope and rock types, suggesting knick-zone migration has passed that lower region of our study area. The 10Be concentrations measured along trunk streams systematically match local, subcatchment erosion rates, with muted influence from upstream sediment sources. This is consistent with intermittent sediment conveyance between cliff and bench terrain, with sediment storage and localized release associated with ephemeral arroyo systems in the region. Therefore, while detrital cosmogenic nuclide records in transient landscapes may not directly reflect upstream catchment-averaged erosion rates, 10Be inventories can provide insight into unsteady upslope-directed erosion and downslope-directed sediment conveyance in these dynamic landscapes.

Reconciliation as Interdependence

2018 ◽  
Author(s):  
Fanie du Toit
Keyword(s):  
South Africa ◽  
Institutional Arrangements ◽  
Political Transition ◽  
Racial Groups ◽  
Just Society

This chapter endeavors to develop a coherent framework for political transition—as reconciliation. I argue that reconciliation explains how relationships emerge in unfavorable conditions; how once a modest beginning is achieved, cooperation can grow, trust strengthened, and understanding deepened through appropriate processes and institutional arrangements; and how eventually a fundamentally more just society is built—all as part of a comprehensive transitional agenda. In South Africa, reconciliation politics propagated the idea, diametrically opposed to apartheid, that racial groups were fundamentally and comprehensively interdependent. This provided a compelling rationale for taking reconciliation seriously—and twenty-four years on, it still does. Reconciliation embraces a shared future on the basis that this is not only desirable but unavoidable, and turns to deal with a troubled past because it obstructs this future. More broadly, therefore, reconciliation can be described as “working toward fairness and inclusivity, reconciliation entails the mutual acknowledgment, the progressive institutionalization, and the long-term socialization of a comprehensive and fundamental interdependence.”

The Imperial Army Project

2018 ◽  
Author(s):  
Douglas E. Delaney
Keyword(s):  
South Africa ◽  
British Empire ◽  
Second World War ◽  
World War ◽  
Archival Research ◽  
Military Cooperation ◽  
High Point ◽  
The Military ◽  
Second World

How did British authorities manage to secure the commitment of large dominion and Indian armies that could plan, fight, shoot, communicate, and sustain themselves, in concert with the British Army and with each other, during the era of the two world wars? This is the primary line of inquiry for this study, which begs a couple of supporting questions. What did the British want from the dominion and Indian armies and how did they go about trying to get it? How successful were they in the end? Answering these questions requires a long-term perspective—one that begins with efforts to fix the armies of the British Empire in the aftermath of their desultory performance in South Africa (1899–1903) and follows through to the high point of imperial military cooperation during the Second World War. Based on multi-archival research conducted in six different countries on four continents, Douglas E. Delaney argues that the military compatibility of the British Empire armies was the product of a deliberate and enduring imperial army project, one that aimed at ‘Lego-piecing’ the armies of the empire, while, at the same time, accommodating the burgeoning autonomy of the dominions and even India. At its core, this book is really about how a military coalition worked.

scholarly journals Private retirement resorts in South Africa: Guidelines for wellness and sustainability in the long term.

2013 ◽  
Vol 32 (1) ◽  
Author(s):  
Andries C. Hauptfleisch
Keyword(s):  
South Africa ◽  
Knowledge Base ◽  
Quantitative Data ◽  
Qualitative Data ◽  
Well Being ◽  
The Other ◽  
Literature Study ◽  
Optimal Profile

Unsubsidised private retirement resorts in South Africa developed during the last three decades present residents with many challenges. There is no existing generally accepted knowledge base or guidelines to serve this sensitive market. The research objective was to establish which elements are experienced by residents of retirement resorts as satisfactory and which as problematic. A literature study was also undertaken. Quantitative as well as qualitative data were obtained by means of structured questionnaires, interviews and a seminar. The results reported pertain to eight resorts in the east of Pretoria, four in Bloemfontein and two in Knysna. The study is currently being extended to other centres. The quantitative data is arranged in order of the priorities set by the biggest group (Pretoria), with the other groups in comparison. So the research was based on the sourcing of quantitative and qualitative data, as well as on descriptive evaluations. The results offer insightful knowledge and guidelines towards establishing an optimal profile for the development of long-term sustainable private retirement resorts. The implications and value of this study are that both developers of retirement resorts and prospective residents are provided with guidelines to better equip them to evaluate a specific retirement resort with regard to the sustainable well- being of residents long-term.

Is the water permit system a panacea or a bed of inefficiency? The case of South Africa

Water Policy ◽  
2013 ◽  
Vol 15 (4) ◽  
pp. 570-584 ◽  
Author(s):  
Devi Datt Tewari ◽  
Saidou Baba Oumar
Keyword(s):  
South Africa ◽  
Water Distribution ◽  
Water Markets ◽  
Water Management System ◽  
Administrative Costs ◽  
System A ◽  
Access To Water ◽  
License System ◽  
Institutional Efficiency

Although South Africa has adopted a very modern permit/license system to control access to water as a resource, the attainment of the lofty objectives (efficiency, equity and sustainability) of the National Water Act of 1998 depends on two critical factors: (1) the institutional efficiency of the water management system; and (2) the development of water markets and their efficient functioning. This study lists a number of concerns that the Act is not geared to resolve efficiently or in a timely manner. These concerns include the high administrative costs of implementation, poor incentives for long-term investments, bureaucratic inefficiency, practical problems in water pricing and adaptability to climate change threat. There is a need to re-think the ways and means with which to make water distribution more efficient in the country. One possible solution would be to develop water markets in the country.

Sign in / Sign up

Export Citation Format

Share Document