Developing risk set-back lines for coastal protection using shoreline change and climate variability factors

Abstract

Goble, B.J. and Mackay, C.F. 2013. Developing risk set-back lines for coastal protection using shoreline change and climate variability factors. Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 2125–2130, ISSN 0749-0208.-->In a changing climate, coastal zones are increasingly susceptible to coastal hazards. In South Africa this is exacerbated by growing pressure for coastal frontage development. Hence the recognised, urgent need to better control and manage development in the coastal zone. A formal guideline in this regard, is the development of coastal set-back lines to ensure new development is protected from coastal events and slower, climate driven changes. Authorities concerned over potential hazards in the coastal zone are now thinking of how to determine and implement risk set-back lines. This paper presents the stepwise process arrived at, to determine such a risk set-back line for KwaZulu-Natal. The process is simple, cost-effective and considers three key factors; historical shoreline change, sea-level rise and coastal vulnerability. For this study, three set-back line lifespans where considered; 25, 50 and 100 years. This time range allows for both long-term management and short-term understanding of coastal risks and vulnerability. Set-back lines for the three time scenarios range from 0 to 99m, 198m and 394m respectively. The methodology is robust and easily repeatable, and has been designed in such a manner that alternative or additional data can be easily included and the methodology can be refined over time. The delineation and enforcement of risk set-back lines is a quick solution to address the pressing problems of coastal KZN, and should also ensure effective short- to medium-term management of the coast.