BARRIER/ESTUARINE PROCESSES; BOT RIVER ESTUARY—AN INTERPRETATION OF AERIAL PHOTOGRAPHS

Abstract

SUMMARY Bot River estuary can be classified as an end-member stage of a bar-built estuary, occupying a drowned river valley. The modern barrier consists of fairly large back-barrier dunes, hummocky foredunes and a dissipative beach. Aerial photographs were interpreted to assess whether the estuary has during modern times always had its present configuration, and to interpret the present physical processes based upon changing morphological features. Lowering of sea-level following the Late Holocene high-water stand exposed a sandy strand plain between Kleinmond and Hawston. Wind action forced an eastward transport of these sands creating a large dune field between Sonesta and Hawston, and a deflation surface at Rooisand. In 1938 the Lamloch swamps were well vegetated but by 1981 large formerly vegetated areas had been converted to open water as a result of subsidence. Long periods of mouth closure forced high water-levels in the estuary which flooded the deflated Rooisand area. Eventually estuarine waters ...