Coastal vulnerability assessment: a case study in Kien Giang, western part of the Mekong River Delta in Vietnam

Climate change, particularly sea-level rise, threatens low-lying coastal systems, such as small islands on coral atolls, and deltas where millions of people are living. The Mekong River Delta is considered especially at risk. Although most of the delta is only a few metres above sea level, there have been few assessments of vulnerability at local scale. The aim of this thesis is to provide quantitative and qualitative information to guide the process of adaptation and provide visualisations that will enhance local authority’s decision making to adapt to climate change, particularly sea-level rise. It focuses on the seven coastal districts within Kien Giang province in the western, micro-tidal section of the delta. A framework is adopted that integrates biophysical effects and socioeconomic stressors for the case study area and consists of three main components of vulnerability: exposure, sensitivity, and adaptive capacity. The analytical hierarchical process (AHP) method of multi-criteria decision making was integrated directly into a geographic information system (GIS) to derive a composite vulnerability index that indicated areas or hotspots most likely to be vulnerable to sea-level rise. The hierarchical structure comprised three components: exposure, sensitivity and adaptive capacity (level 1); and eight sub-components (level 2): seawater incursion, flood risk, shoreline change, population characteristics, landuse, as well as socioeconomic, infrastructure, and technological capability. The Digital Shoreline Analysis System (DSAS) tool was used to calculate rates of shoreline change along the Kien Giang coast over time in order to derive the shoreline change sub-component that contributed to the exposure component. Beyond this, a further 22 variables (level 3) and 24 sub-variables (level 4) related to vulnerability were also mapped. Based on the weights of variables derived from AHP pair-wise comparisons, a final map was generated to visualise areas reported into five categories of relative vulnerability; very low, low, moderate, high to very high vulnerability. Several regional patterns emerged. Relatively high exposure to seawater incursion, flood risk, and moderate loss of mangroves characterised the coastal fringe of each district. Those areas found to be most sensitive tended to have moderate population density, generally with a large rural population and high proportions of ethnic households with limited availability of agricultural land. Many aspects of adaptive capacity could only be represented at district scale, with the least adaptable areas consisting of large proportions of poor households, low income, and moderate densities of transport, irrigation, and drainage systems. Finally, most coastal districts were determined to be of moderate to relatively high vulnerability, with scattered hotspots along the Kien Giang coast, which coincided with settlement areas. The results obtained, enable identification and prioritisation of the areas, or hotspots most likely to be vulnerable, for which site-specific assessments might further assist the local authorities and communities in better coastal management and conservation. However, the limitations of data accessible at an entire district can influence the outcome. Social vulnerability remains a challenge because it is changing over time and space.