Abstract
The frequency and magnitude of floods have increased due to natural phenomenon and human developmental activities in the areas of Mbashe (N2) and Port Alfred (R72) roads, Eastern Cape Province, South Africa. Climate change has contribution for the change of flood occurrence in the area. The aim of this study was to investigate the causes of culvert failures due to changes in local conditions (hydrology and hydraulics), focusing on the methodology of determining the existing culverts capacity and comparing them to the peak floods for the purpose of hydraulic sufficiency and insufficiency. In addition, the procedure also consisted of determining the Shoulder Break Point (SBP) of the existing culverts and comparing them against headwater depth due to floods to evaluate sufficiency and insufficiency in overtopping. It was found that majority of the existing culverts from N2 and R72 roads were hydraulically insufficient because of the peak floods being greater than the existing capacity of the culverts. In addition, most of the culverts were found to be insufficient in overtopping because of the SPB being less than the headwater depth due to floods. Consequently, most of the culverts are found to be eroded, silted and cracked. Human developmental activities should be minimised in a strictly manner to lower the flood magnitude and frequency. The route managers should ensure an effective routine road maintenance (RRM) plan for removal of silt and debris as a more economical strategy.
M.Phil. (Civil Engineering Science)