An investigation of the movement of sediment through the Noordhoek headland bypass dunefield system at Cape Recife, South Africa

A detailed study of the movement of sediment across the Cape Recife headland via the Noordhoek headland bypass dunefield was conducted. The Noordhoek HBD is important because of the environmental impacts anticipated on the sewerage works, settling ponds, and road to the Cape Recife lighthouse situated in the migration path of the dunefield to the ENE of its active boundary. The primary objective of the study was to investigate the movement of sediment in and through the Noordhoek HBD system. This study has provided sand transportation and dune migration rates by making use of various dune monitoring techniques. In doing so, useful predictions have been made as to when the settling ponds and the road to the lighthouse will be inundated. An indication has also been given as to how much sand moves through the system. Some key findings from this research included: the net migration direction of the Noordhoek HBD was found to be towards the east-north-east; the wind environment at the study area was classified as a high energy wind environment; this study has highlighted that various climatic factors such as rainfall and temperature influence the movement of sediment through dune systems; sediment transport was found to be directly related to the source area and topography; the central zone of the dunefield proved to be a groundwater recharge zone for the western and eastern zones; and the leading lobes of the migrating Noordhoek dunefield are gradually covering stabilising vegetation by pulses of dunes moving through. In this study, it was calculated that presently a total volume of about 26 000 m3 of sand is migrating into the vegetation at the leading lobes annually. If the Noordhoek HBD is left to run its natural course and migrate across the Cape Recife headland to the downwind beach, an approximate volume of 26 000 m3 of sand could be supplied to the downwind beach by this system. In doing so, it has the potential to play a role in replenishing some of the sand to Port Elizabeth’s eroded southern beaches via a natural process