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

Theron, Andre Karl (2016-03)

Thesis (DEng)--Stellenbosch University, 2016.

Thesis

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.

AFRIKAANSE OPSOMMING: Die implementering van die Geïntegreerde Kusbestuurs-wetgewing van 2008 het dit ‘n wetlike vereiste gemaak om kus-ontwikkelings-terugsetlyne te bepaal in al die kusprovinsies van Suid-Afrika. Kus-ontwikkelings-terugsetlyne (ook bekend as kus-bestuurslyne) moet voorsiening maak vir fisiese kus/mariene prosesse, asook “sagter” meer subjektiewe aspekte en oorwegings, byvoorbeeld omgewingsimpakte, publieke toegang, erfenis, estetika/besienswaardigheid, gewaarwording van skoonheid/”plek-sin” (‘sense of place”), ens. ‘n Literatuur oorsig sowel as onlangse werkswinkels wat in Suid-Afrika gehou is oor terugsetlyne, het beklemtoon dat daar ‘n gebrek is aan konsekwente metodes/tegnieke om terugsetlyne te bepaal, asook dat daar grootskaalse verwarring heers oor hoe om met die bepaling daarvan voort te gaan. Die literatuur oorsig het bevind dat die primêre kusproses-komponente van terugsetlyne verband hou met vloedhoogtes langs die kus sowel as kuserosie. Beide hierdie komponente asook sub-komponente, was onbevredigend hanteer in die metodes wat tot dusver toegepas is. Om hierdie probleme te oorkom, word toepaslike terugsetlyn metodes benodig, wat geskik is vir beperkte data beskikbaarheid. Dié metodes moet ook effektief toegepas kan word in groot studie-areas, maar moet steeds betroubaar en onaanvegbaar wees. Dit is duidelik dat in die lig van Suid-Afrika se algemeen baie blootgestelde kuslyn (en die moontlikheid van ergerwordende klimaatsveranderings-impakte), die snelgroeiende Suid-Afrikaanse kusontwikkeling, en bogenoemde ander probleme, daar die behoefte bestaan vir toepaslike, praktiese en implementeerbare metodes om terugsetlyne te bepaal. Hierdie tesis beskryf die outeur se navorsing oor metodes om kus-ontwikkelings-terugsetlyne in Suid-Afrika te bepaal, en is sterk gefokus op die abiotiese (geofisiese) komponente/aspekte van terugsetlyne. Geofisiese kus-gevare en ruimtelike kwesbaarheid, en hul belang vir/op terugsetlyne word oorweeg. ‘n Praktiese kus-gevaar en kwesbaarheid evaluerings-tegniek, voorheen toegepas op Europese kus-toestande, maar toepaslik vir Suid-Afrikaanse toestande en data beskikbaarheid, is aangepas en verder ontwikkel (gebaseer op metodes voorgestel deur Theron et al, 2010a, 2012), om bykomende faktore in te sluit wat toepaslik is vir Suid-Afrikaanse toestande. Na ‘n uitgebreide literatuur oorsig en die toets van verskeie golf-oploop modelle teen plaaslike data, is bevind dat die modelle van Nielsen en Hanslow (1991) en Mather et al (2011) die bestes is van die beskikbare modelle en dat hul voldoende is vir toepassing in Suid-Afrika, maar dat hul gebruik behoort te word met sekere aanpassings soos in hierdie tesis aanbeveel word. Nuwe metodes is ontwikkel en twee alternatiewe benaderings word voorgestel om korttermyn kus-erosie te voorspel, wat minder invoer data benodig, en wat ook geskik is vir toepassings op groter skaal (eerder as om beperk te word deur die tekortkominge van gebruiklike metodes). Huidige metodes om terugsetlyne te bepaal het nie duin-effekte voldoende in ag geneem nie. Daar word dus ‘n nuwe benadering voorgestel om duin-effekte op normale kusereosie beramings te kwantifiseer. Ander belangrike komponente van, en benodigdhede vir terugsetlyne word ook behandel. Besprekings en spesifieke aanbevelings, voorstelle en riglyne word voorsien wat handel oor ‘n verdere agt komponente/aspekte wat benodig word vir die bepaling van terugsetlyne. Ten slotte word al die benodigde terugsetlyn-medodes en aspekte bymekaar gebring, en word daar verduidelik hoe hul toegepas behoort te word. Al die basiese komponente word gelys en ‘n samestelling van die stappe wat benodig word om kus-ontwikkelings-terugsetlyne te bepaal, word gegee. Aanbevole prosedures en metodes word gegee om elk van die stappe uit te voer en te voltooi.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98515
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