Coastal vulnerability analysis of Bangladesh coast using fuzzy logic based geospatial techniques

Abstract

Bangladesh coast is recognized as one of the hotspots of several coastal hazards like coastal flood, sea level rise, increased tropical cyclone occurrence etc. To understand the problem followed by necessary coastal management recommendation, an integrated coastal vulnerability index i.e., Composite Vulnerability Index (CVI) was developed for the coastal region applying geospatial technique. Three sub-indices, namely, Coastal Characteristics Vulnerability sub-index (CCVI), Coastal Forcing Vulnerability Sub-index (CFVI) and Socio-economic vulnerability sub-index (SEVI) were separately estimated and combined to determine the CVI. Since, the classical set theory of traditional vulnerability classification is inadequate to express the natural variability of vulnerability at continuous scale, this study offered a framework of vulnerability representation using fuzzy set theory. The approach was effective to handle the uncertainty of large scale vulnerability analysis with the normalization of featured factors applying three fuzzy membership functions i.e., Fuzzy-Large, Fuzzy-Small and Fuzzy-Linear in geospatial analysis. The analysis was carried out at 10 m cell level and classified with five vulnerability classes i.e., very high, high, moderate, low and very low. The analyses show that the Chittagong coast and Feni district are very highly vulnerable. High tide amplitude (>4 m), cyclone track density and mild coastal slope are responsible for the high vulnerability of the Chittagong coast. On the other hand, Feni district shows the highest SEVI which is resulted from high population density and socio-economic conditions. Presence of mangrove forest results a reduced CFVI which significantly decrease the vulnerability of Pirojpur, Satkhira, Khulna and Bagerhat district. Based on the responsible vulnerability index, necessary coastal protection measures are recommended for the coast. It is expected that the comprehensive vulnerability map with CVI can be a key element for coastal management of Bangladesh. Furthermore, the classification of vulnerability under different class will help to develop necessary coastal protection measures according to the resiliency of the coastal community.