ESTUARIES IN SOUTH AFRICA

Useful links

Main Page	General Information	Catchment Characteristics	Land and Estuary Uses	Ecology
Threats	Water Quality	Physical Features	Climate	References
SWARTLINTJIES RIVER ESTUARY: Hydrodynamics and mouth dynamics

	Hydrodynamics
	Waves strike the coastline mainly from the SW and SSW. According to J. Rossouw (pers.comm) wave heights of 1,6m are reached for 50 percent of the time at Oranjemund which is approximately 170km north of the Swartlintjies Estuary. The wave frequency has been recorded as 10-15 seconds at Buchu Bay, approximately 150km north of Swartlintjies by Ashby et. al. (1973) (Ref 1)
	A series of outward flowing rip currents 100 to 200 m apart extending northwards along the bay indicated nearshore "cell" circulation, with a nett northward flowing longshore current at the time of the ECRU survey. (Ref 1)
	The ECRU survey took place one day before Neap tide and the tidal range between Mean High Water Spring and Mean Low Water Spring at Port Nolloth is recorded as being 1.57m. (S.A Tide Tables 1980). (Ref 1)

	Mouth dynamics
	The rivermouth is situated close to a rocky promontory in a north-facing bay. A triangular dunefield of bare transverse barchanoid dunes fan out northwards from the rivermouth for a distance of approximately 1,6km. Another less prominant rocky point is found at the northern end of the bay 1,8 km from the rivermouth.
	The dune-plume to the north of the Swartlintjies mouth and its present configuration has been attributed to changes in sea-level and subsequent movements of the river mouth sediment source.
	The shoreline along the bay consists of a steeply shelving terraced beach, the slope of which is accentuated near the mouth by the embankments of the two excavated trenches running parallel to the shore. (Ref 1)