Natural and human induced indicators in coastal vulnerability and risk assessment

Περίληψη

Climate change has significant repercussions on the natural environment, triggering changes in the natural processes that might have a severe socio-economic impact on the coastal zone; where a great number of human activities are concentrated. So far, the estimation of coastal vulnerability has been based, primarily, on the natural processes and, secondarily, on socioeconomic variables, which would assist in the identification of vulnerable coastal sectors. The present investigation proposes a methodology to examine the vulnerability of a highly touristic area in the Island of Crete to an expected sea level rise of up to ~40 cm by the year 2100, according to the A1B scenario of IPCC 2007. The methodology is based combination of socio-economic indicators and existing natural indicators, GIS-based, of the coastal vulnerability index (CVI) for sea level rise and related wave-induced erosion. This approach includes three sub-indices that contribute equally to the overall index. The sub-indices refer to coastal forcing indicators related to extreme natural events; (ii) socio-economic indicators, such as those of population, cultural heritage sites, transport networks, land use and protection measures; and, (iii) indicators of coastal characteristics that refer to both geological variables (i.e., coastal geomorphology, historical coastline changes, and regional coastal slope) and marine rocesses (i.e., relative sea level rise, mean significant wave height, and tidal range). All variables are ranked on a 1-5 scale with the rank 5 indicating the highest vulnerability. The socio-economic sub-index includes, as indicators, the population of the study area, cultural heritage sites, transport networks, land use and protection measures. The coastal forcing sub-index includes the frequency of extreme events, while the Coastal Vulnerability Index includes the geological variables (coastal geomorphology, historical coastline changes, and regional coastal slope) and the variables representing the marine processes (relative sea level rise, mean significant wave height, and tidal range). The main difficulty for the estimation of the index lies in assessing and ranking the socio-economic indicators. The whole approach was tested and validated through field and desktop studies, using as a case study the Elounda bay, Crete Isl.; an area of high cultural and economic value, which combines monuments from ancient and medieval times, with a very high touristic development since the 1970s.