ESTUARIES IN SOUTH AFRICA

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VERLOREVLEI RIVER ESTUARY: Catchment Characteristics

	Main Rivers and tributaries
	The catchment is about 87km long in a north-west/south-east direction and up to 43km wide. Its surface area is estimated (Ref. 5) to be 1 890km², or 198 000 ha.
	The catchment is bounded by the Swartberg and Olifantsrivierberge in the east and by the Piketberg in the south, and includes the Eendekuil basin, a low-lying area lying between the Olifantsrivierberge and the Piketberg. The Verlorenvlei River and its tributaries drain the entire Eendekuil basin, the Table Mountain Group mountains around Paleisheuwel, the northern outliers of Piketberg, the extensive flats of Tertiary to Recent sands between Het Kruis and Redelinghuys and the 5km strip of low Table Mountain Group hills and sand flats on either side of the lake which contribute seepage (Ref. 1).
	Dams

	River run-off

	Geomorphology
	Von Harmse (Ref. 3), in his Schematic Soil Map of Southern Africa (1978), classifies the Verlorenvlei area as a zone of littoral sands which are arenosols, or of aeolian origin. He points out that the salient feature of such soils is their low reserve of weatherable minerals, and the low silt/clay ratio. Taylor (1987) describes these coastal lowlands as consisting of sands and conglomerates of Tertiary to Recent origins. He comments on their low water-retaining capacity, being either acid and relatively infertile or, nearer the coast, alkaline with a distinct horizon of lime accumulation. The 'heuweltjies' or hillocks have higher clay content than the surrounding soils (Ref. 4).
	The general Verlorenvlei area is characterized by type a fine sandy soil, in which the dominant types are Fernwood and Mkambathi; the sub-dominant Hopefield; and the rare Langebaan, Sandveld and Sonneblom. On the southern bank, extending from Elandsbaai to Redelinghuys, are isolated sections classified as rock and undifferentiated lithosols.
	Rubble and debris are found in numerous places at the foot of cliffs and along small streams that flow down hillsides after heavy downpours. The river is flanked by strips of alluvium, part of it being black and rich in plant material. Several patches of drift sand and bare dunes away from the coast originated mostly from mismanagement of the veld. A large dune field occurs to the north of the river mouth and the town of Elandsbaai

	Geology
	The Malmesbury Group (Proterozoic) has been subdivided on purely lithological grounds into three groups, calcareous, quartzose and phyllite with greywacke. The calcareous group comprises pure limestone, dolomitic limestone and dolomite. Carbonaceous patches and calcareous rocks grade into quartz-rich varieties.
	Sediments showing a high degree of lithological similarity to the Klipheuwel beds of the type area are found in small occurrences along Verlorenvlei. No angular inconformity is visible between them and the Table Mountain Group but their regional relationships clearly show the presence of an inconformity. Rogers named these rocks Ibiqua Beds, which implies a correlation with the Nama System, for which there is no proof available yet (Ref. 2).
	The Klipheuwel Formation (Proterozoic) comprises the following: purple to red-dish brown sandy micaceous shale which is mostly poorly-bedded and grades into mudstone; alternating beds of sandstone, shaly sandstone and sandy shale with colours ranging from buff to purple and red; white and brightly coloured sandstone and grit with minor conglomerate and shale layers. The arencaeous strata are commonly cross-bedded, quite often feldspathic, and much softer than the Table Mountain Group sandstone. The maximum thickness exposed on the eastern boundary of this area amounts to about 375m.
	White to slightly-reddish sandy soil originated mainly from the underlying unconsolidated to partly-consolidated sand and clay, and to a lesser extent from the Table Mountain Group, the coastal dunes, and fluviatile deposits of past and present drainage systems.