Revision of the Macro Climatic Regions of Southern Africa
8 Pages Posted: 21 Oct 2013
Date Written: October 21, 2013
Factors influencing pavement designs are divided into two, namely controllable and non-controllable. Controllable factors include engineering design, selection of materials, construction quality and control, standards and progress. Uncontrollable factors include climate, terrain and geological conditions such as surface and sub-surface hydrology. Therefore there are many influential factors that the engineer cannot control and hence understanding risk and reliability is a key aspect of design to cater for uncertainties. It is believed that by the year 2100, world climate will have changed in ways that are difficult to imagine - as difficult as it would have been at the end of the 19th century to imagine the changes of the 100 years since. The current heat, drought, floods and rainfall spurts are evident of the effects of climate change. The response to climate change is often seen as twofold; adaptation and disregard. Adaptation often viewed as the most essential part of the response to the threat of climate change whereas disregard comes from a poor understanding of the influential factors of the African climate. Severe lack of local weather data, particularly for central Africa is also part of the problem. This lack of knowledge makes it very difficult to predict with any degree of accuracy what will happen as a result of climate change at a country, or even sub-regional level in Africa. Extensive research has been done by climatologists on the subject of climate change. However, engineers and technologists have not yet adapted an approach that aims to address the topic within the engineering sector. Improvements ought to be made particularly on climate based parameters used in transportation engineering and designs. The Macro Climatic Regional Map of Southern Africa adopted from Weinert (1980) by Technical Recommendations for Highways (TRH4) (1994) is one of the most outdated weather based catalogues used in the industry. To date, even in light of the eminent threat of climate change, no credible advances have been made yet for any improvements on this over thirty year old design climatic regional map. Minor editions on the Weinert N-Values include up to ten percent adjustments on net cold binder whereby an increase is made on dry areas (N-value > 5) and reduction in wet/humid areas (N-value < 2). A gap therefore exists and speedy research is imperative in order to optimize our roads’ serviceable life and also keep abreast with the ever changing environmental factors influencing our roads. The methodology adopted in this study included identifying and mapping areas within the Southern African region that may suffer from future increased precipitation and flash flooding among other climate based parameters. Results of preliminary analysis indicate a shift in rainfall patterns within the region where increases in rainfall per annum are expected in the central Free State and North escarpment of the Eastern Cape provinces in South Africa. In future there shall be more moderate and wet areas than when the original map was adopted. Areas characterised as dry such as the Western Cape and the Karoo shall be now described as moderate. Another visible change on the map is the increase from three different climatic regions to six.
Keywords: Weinert N-value, flooding, climatic regions, environmental factor, climate change
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