Methods for determination of coastal development setback lines in South Africa.

[摘要] ENGLISH ABSTRACT: Implementation of the ICM Act (2008) has made it a legal requirement to determine coastal setback lines in all the coastal provinces of South Africa. Coastal development setback lines (or 'coastal management lines) need to make provisions for physical coastal/marine processes, as well as 'softer more subjective issues and considerations, e.g. environmental, public access, heritage, sense of place, aesthetics, etc. Both the literature review and recent setback line workshops held in South Africa have highlighted the lack of consistent methods to determine setback lines, as well as the major confusion around how to proceed. The literature review found that the primary coastal processes components of setback lines were related to coastal flooding levels and coastal erosion. Both of these, including sub-components, were not satisfactorily dealt with in terms of methods applied to date. To alleviate these problems, appropriate setback line methods are sought for 'data poor environments, that can be efficiently applied in large study areas, but that are still sufficiently robust and defendable. In view of South Africa's generally very exposed coastline (and the possibility of progressive climate change impacts), the escalating South African coastal development, and the above mentioned problems, the need for appropriate, practical and implementable methodologies to determine setback lines is clear.This thesis describes the author's research concerning methods for the determination of coastal development setback lines in South Africa, and focuses strongly on the abiotic (geophysical) components of setback lines.Geophysical coastal hazards and spatial vulnerability, and their relevance to setback lines are considered. A practical coastal hazard and vulnerability evaluation technique, applied to European coastal conditions but applicable to South African conditions including poor data availability, was adapted and further developed (building on methods proposed by Theron et al, 2010a, 2012), to include additional forcing factors considered to be relevant under South African conditions.Following an extensive literature review and testing of several different wave runup models against local data, it is concluded that the models of Nielsen and Hanslow (1991) and Mather et al (2011) are the best of the available models and are adequate for application in South Africa, but should be used with certain adaptations as recommended herein. New methods were developed and two alternative approaches are proposed to predict short-term shoreline erosion, requiring less input data, and that are also suitable for larger scale approaches (rather than being limited by the constraints of conventional methods). Current methods of determining setback lines have not adequately taken dune effects into account. Thus a novel approach is proposed for quantifying dune effects on normal shoreline erosion estimates.Other important components of and requirements for setback lines are dealt with. Thus discussions and specific recommendations, suggestions and guidance are provided on another eight components/aspects necessary for determining setback lines. Finally, all the necessary setback line methodologies and aspects are put together, explaining how they should be applied. The basic components are catalogued and a compilation of the steps required to determine coastal development setback lines is provided. Recommended procedures and methods for conducting/completing each of the steps are given.

[发布机构] Stellenbosch University