ESTUARIES IN SOUTH AFRICA

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GROOT BRAK ESTUARY: Hydrodynamics and mouth dynamics

	Hydrodynamics



	Mouth dynamics
	The Great Brak river village museum contains photographs taken in 1920, 1943, 1956, 1970 and 1973 which show typical changes at the lower estuary and of the tidal inlet. (Ref 1)
	1920: The island is almost unaltered from the natural state. A sandbar blocks the southern channel while the northern channel carries more water than can be seen on later photographs. (Ref 1)
	1943: The water-level around The Island is high (floods?). The northern channel is in full flow whereas the southern channel is closed by a sandbar behind which lies a pool. (Ref 1)
	1956: The situation is similar to that prevailing during the ECRU survey of November 1981. The southern channel is open and joins the northern channel at the sea front of The Island. Influx of sea sand is detectable in the form of streamlined sandbanks in the northern channel which overlap the Prawn Island (the large mud bank northwest of The Island). (Ref 1)
	1970: Little water in the northern channel with water concentrated against the steep rocky bank on the east side. Complete closure of the southern channel by a sandbar. ({Photograph probably taken during low water spring tide). (Ref 1)
	1973: The northern channel is open and the southern channel is closed except for a narrow stream of water around the sea side of The Island (probably photographed during low water spring tide). (Ref 1)