Assessment of the Coastal Vulnerability Index (CVI) for disaster mitigation strategies in some coastal tourism areas in Gunungkidul, Yogyakarta-Indonesia

Abstract

South coastal area of Gunungkidul, Yogyakarta-Indonesia has a high tourism development due to the unique physical conditions of coastal typology. However, during the last few years, extreme wave height associated with cyclones damaged many tourist facilities there. Coastal management for ecosystem sustainability requires disaster mitigation, which one considering the aspect of vulnerability. This study aims to assess the level of coastal vulnerability according to coastal typology of Baron-Pok Tunggal section and to determine the coastal management model based on the level of vulnerability. The Coastal Vulnerability Index (CVI) is used in vulnerability assessment. The variable formulation of CVI is divided into hydrodynamic factors (mean significant wave heights, mean tide range, and mean sea level rise) and morphodynamics factors, i.e. geomorphology, coastal slope, and average width of emerged beach. The morphodynamics data were obtained through observation, direct measurements in the field by systematic sampling, extraction from aerial photographs and digital surface model (DSM). The results of modeling and predictions by several agencies are derived to obtain the hydrodynamics data. The result of this study revealed that marine deposition coast typology have a high and moderate vulnerability (twelve and eleven coastal units, respectively). Meanwhile, a low vulnerability can be found in the cliff coast or wave erosion coast typology (24 units). The convex or concave beaches tend to be more vulnerable than beaches with the straight form. The beaches of Buluk, Drini, Kosakora, Sarangan and all beaches from Krakal to Indrayanti have a high vulnerability. Geomorphological variables, significant wave height, and sea level rise have the strongest influence on vulnerability. Coastal management in the marine deposition coast typology can be carried out either in a protective manner or by accommodative approach, such as by observing changes in natural conditions due to sea level rise.