Beach ridge sets reflect the late Holocene evolution of the St Lucia estuarine lake system, South Africa

Abstract

Sets of sandy beach ridges and intervening swales define shoreline sections of the shallow St Lucia wetland system within the iSimangaliso Wetland Park, World Heritage Site in northern KwaZulu-Natal province, South Africa. The sets comprise 3-10 beach ridges, the most prominent being 80-150 m wide and rising 0.5-2 m above the adjacent swales. The highest beach ridge crests elevated 3.2-4.6 m above mean sea level are furthest from the present shoreline and the lowest ridges, rising about 0.5 m above the swales, occur closest to the present mean lake level shoreline. This investigation assesses the genesis of the sandy beach ridges on five strand plain remnants within the estuarine lake. The ridges were topographically surveyed and their ages estimated using optically stimulated luminescence (OSL) dating. OSL dating reveals that the oldest beach ridge formed around 6,240 years ago, with a sequence of beach ridges having accumulated during the period ~4,000 to 1,500 years ago

A morphological classification of coastal forelands, with examples from South Africa

“…Many of the forelands along the northeast coast of South Africa, and the adjacent coastal plains, are anchored on aeolianite and gravel/sand beach ridges that span MIS 11 to Holocene (Porat and Botha, 2008;Botha et al, 2018). For example, the Cape Vital foreland (#71) is located immediately seaward of Lake Bhangazi that has, at its southern end, a beach berm <6 m asl dated by the luminescence method to 1800±160 yr (Botha et al, 2018). Progradational development of the Cape Vital foreland therefore postdates this period.…”

Contrasting beach‐ridge systems in different types of coastal settings

“…One of the most widely application of beach‐ridge systems is as archives of changes in climate and relative sea/lake level (Argyilan et al, 2010; Botha et al, 2018; Brooke et al, 2019; Hede et al, 2013; Hein & Ashton, 2020; Oliver et al, 2015; Otvos, 2000; Sander et al, 2015). Besides sea‐level variations and long‐term changes, the elevation of individual ridges have been explained as the result of wave height conditions, tidal and eolian processes, wind strength, sediment supply, and general local coastal dynamics (Rodríguez & Meyer, 2006; Sander et al, 2015).…”

Boundary Determination of Lake-Type Wetland Park Based on GIS Multifactor Analysis

“…China started individualized study on “wetland park” since the beginning of the twenty-first century. At present, the boundary of “wetland park” is determined mainly in the form of “ecological redline” [ 7 , 8 ], which was clearly put forward in the Opinions of the State Council on Strengthening the Key Work of Environmental Protection in 2011: the ecological redline shall be defined in major ecological functional areas, sensitive areas of land and marine ecological environment, vulnerable areas, etc. As the boundary line, and management and control line of the ecological area, the ecological redline can cope with the environmental resources constraint pressure ascribed to China's rapid urbanization process effectively and maintain national or regional ecological security and sustainable development, enabling its application to wetland park [ 9 ].…”