Bathymetry of the South African continental shelf

Wet, De; Myburgh, W.J.

doi:10.1007/s00367-021-00701-y

Cited by 23 publications

(8 citation statements)

References 56 publications

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“…For this study, sites between Durban and Richards Bay were selected for MBES mapping based on (1) features identified on low-resolution regional datasets 40,52 (and references therein) (2) being known recreational fishing areas (likely reefs) and (3) their location relative to the uThukela MPA management zones. Hydroacoustic surveys were carried out on the reefs and their adjacent areas in the 40-100 m depth zones, depending on site location.…”

Section: Methodsmentioning

confidence: 99%

“…36,37 The availability of high-resolution bathymetric data has increased modelling capabilities in marine science. 18,30,[38][39][40][41][42] However, MBES data are only one component (although an important one) of benthic habitat mapping, which requires various inputs (e.g. seabed imagery, sediment samples, backscatter and bathymetry).…”

Section: Introductionmentioning

confidence: 99%

“…Benthic habitat mapping is recognised as a need to be expanded upon in South Africa 41 , because the continental shelf bathymetry has been previously recognised to be poorly resolved 40 . One of the benthic habitats recognised globally for the multitude of coastal goods and services it offers is reefs 46 (i.e.…”

Section: Introductionmentioning

confidence: 99%

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The value of multibeam bathymetry in marine spatial planning in South Africa: A review

Wanda,

Wiles,

Cawthra

et al. 2023

S. Afr. J. Sci.

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Given a growing global population and shift to embrace the blue economy, a need for marine spatial planning (MSP) has emerged in South Africa to sustainably resolve the rising conflicts over the use of marine and seabed resources and services. A well-developed marine spatial plan yields numerous ecological, social and economic benefits. These are achieved through mediating between spatially conflicting economic drivers’ interests (e.g. commercial fishing, tourism, mining), preventing their activities from compromising thresholds of an environment’s sustainability. Within the MSP framework, high-resolution geospatial datasets are required to document and describe the seabed in the highest possible detail. At any scale, integrated analysis of seabed geomorphology and habitats is anticipated to greatly improve the understanding of ecosystem functioning from a multidisciplinary perspective, whilst improving MSP procedures and management of marine space. South Africa is the first of few African countries to have an approved and implemented MSP framework, but is still somewhat behind globally in implementing large-scale regional hydroacoustic surveys to cover the country’s vast offshore territory. The deficiency of hydroacoustic surveys is perhaps due to a relative lack of funds and poor communication about the value of multibeam echo-sounder (MBES) derived data, whilst marine geoscience remains a scarce skill in the country. This review paper presents a geological perspective of MSP and explores (1) the value that seabed mapping offers MSP specifically and (2) the need to increase seabed mapping with MBES, using a recently initiated project from the South African east coast as a case study.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The value of multibeam bathymetry in marine spatial planning in South Africa: A review

Wanda,

Wiles,

Cawthra

et al. 2023

S. Afr. J. Sci.

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“…The study area is South Africa's mainland maritime domain (i.e., territorial seas plus exclusive economic zone), which extends from the dune base (Harris et al, 2019) to 200 NM seaward (Figure 1). The width of the continental shelf varies between 1.3 and 260 km, and the depth of the shelf break ranges between 80 and 600 m (de Wet and Compton, 2021). The western continental margin is wide and deep and terraced in places (de Wet and Compton, 2021), and tapers in a southern-easterly direction.…”

Section: Study Areamentioning

confidence: 99%

“…The width of the continental shelf varies between 1.3 and 260 km, and the depth of the shelf break ranges between 80 and 600 m (de Wet and Compton, 2021). The western continental margin is wide and deep and terraced in places (de Wet and Compton, 2021), and tapers in a southern-easterly direction. The southern continental margin includes the wide Agulhas Bank resembling the outline of the South African shoreline, and abruptly tapers to the eastern continental margin, which lies parallel to the coastline.…”

Section: Study Areamentioning

confidence: 99%

Iterative mapping of marine ecosystems for spatial status assessment, prioritization, and decision support

et al. 2023

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South Africa has taken an iterative approach to marine ecosystem mapping over 18 years that has provided a valuable foundation for ecosystem assessment, planning and decision-making, supporting improved ecosystem-based management and protection. Iterative progress has been made in overcoming challenges faced by developing countries, especially in the inaccessible marine realm. Our aim is to report on the approach to produce and improve a national marine ecosystem map to guide other countries facing similar challenges, and to illustrate the impact of even the simplest ecosystem map. South Africa has produced four map versions, from a rudimentary map of 34 biozones informed by bathymetry data, to the latest version comprising 163 ecosystem types informed by 83 environmental and biodiversity datasets that aligns with the IUCN Global Ecosystem Typology. Data were unlocked through academic and industry collaborations; multi-disciplinary, multi-realm and multi-generational networks of practitioners; and targeted research to address key gaps. To advance toward a more transparent, reproducible and data-driven approach, limitations, barriers and opportunities for improvement were identified. Challenges included limited human and data infrastructure capacity to collate, curate and assimilate many data sources, covering a variety of ecosystem components, methods and scales. Five key lessons that are of relevance for others working to advance ecosystem classification and mapping, were distilled. These include (1) the benefits of iterative improvement; (2) the value of fostering relationships among a co-ordinated network of practitioners including early-career researchers; (3) strategically prioritizing and leveraging resources to build and curate key foundational biodiversity datasets and understand drivers of biodiversity pattern; (4) the need for developing, transferring and applying capacity and tools that enhance data quality, analytical workflows and outputs; and (5) the application of new technology and emerging statistical tools to improve the classification and prediction of biodiversity pattern. South Africa’s map of marine ecosystem types has been successfully applied in spatial biodiversity assessment, prioritization to support protected area expansion and marine spatial planning. These successes demonstrate the value of a co-ordinated network of practitioners who continually build an evidence base and iteratively improve ecosystem mapping while simultaneously growing ecological knowledge and informing changing priorities and policy.

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Sedimentology of False Bay (Western Cape, South Africa): geological background information for the integrated environmental management of a physically confined coastal compartment

Flemming

2024

J Coast Conserv

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False Bay is a large, physically confined embayment located along the southwest coast of South Africa. It is a classic example of a coastal compartment or littoral cell that acts as a receptor and sink of both terrestrial (siliciclastic) and marine (bioclastic) material. It is almost square in shape, measuring ∼35 km N-S and ∼39 km W-E and covering ∼1130 km2. Only a few small rivers discharge into the bay, as a consequence of which only small amounts of sediment are episodically supplied to the bay. The bathymetry reveals two well-defined terraces, one between 30 and 45 m, the other between 50 and 55 m water depth, which are indicative of extended Pleistocene sea-level stillstands. Sediment is dispersed by long-period ocean swells approaching from the southwestern quadrant, as well as nearshore swell- and wind-driven currents. The presence of a prominent rock pinnacle at the entrance to the bay (Rocky Bank) causes wave orthogonals to converge on its leeward side, and which results in substantial wave amplification along the eastern shore of the bay. Coarse-grained sediments (gravel, very coarse sand, coarse sand and medium sand) line the rocky shores in the west and east, and are dispersed around and away from submarine rock outcrops, whereas fine-grained sediments (fine sand, very fine sand and mud) are largely confined to an arcuate belt extending along the centre of the bay from shallow water in the northwest to the deepest parts in the south. This is documented by the distribution of individual size fractions and the mean grain size, and applies to both the siliciclastic and the bioclastic sediment components which appear to be in hydraulic equilibrium. There is a distinct N-S gradient from lower to higher bioclastic content with increasing water depth. The textural parameters (mean grain size, sorting and skewness) reveal the existence of two hydraulic populations that are mixed in various proportions in the course of their dispersal in the form of either bed load or suspended load transport. The mud fraction is closely linked to the dispersal pattern of the fine and very fine sand fractions, indicating that it is transported in the form of aggregates and/or faecal pellets, the bulk of which is evidently in hydraulic equilibrium with the finer-grained sands. It can be anticipated that, during lower Pleistocene sea levels, the palaeo-False Bay valley was occupied, or at least regularly visited, by large and small African mammals and early humans.

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Bathymetry of the South African continental shelf

Cited by 23 publications

References 56 publications

The value of multibeam bathymetry in marine spatial planning in South Africa: A review

The value of multibeam bathymetry in marine spatial planning in South Africa: A review

Iterative mapping of marine ecosystems for spatial status assessment, prioritization, and decision support

Sedimentology of False Bay (Western Cape, South Africa): geological background information for the integrated environmental management of a physically confined coastal compartment

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