COASTAL HAZARDS: VULNERABILITY OF COASTAL POPULATION USING GIS

The present study estimates the population along the coastal counties of Texas which are vulnerable to hurricane related coastal hazards. Understanding the distribution of population along the Texas coast is vital for damage control during coastal hazards. A regional coastal vulnerability for the Texas coast has not been done at this scale or with the demographic data. There have been several attempts to calculate the vulnerability of the populations along coastal areas. Susan Cutter (1997) used a vulnerability index at county level adding a social context to the physical vulnerability. The physical vulnerability in her study is the probability based on the incidences of natural hazards from historical records. Certain socio-economic factors, that make a population more vulnerable, were taken into consideration. The United States Geological Survey (USGS) (2003) has also come up with a Coastal Vulnerability Index (CVI) calculated based on physical processes and geomorphic characteristics. Cutter’s index does not take the physiography of the landscape into consideration while the USGS CVI does not incorporate the demographic factors of the area. The present study employs land elevation as the primary factor for assessing vulnerability to storm surge. The range of elevations is obtained from 24K DEMs. In a GIS the descriptive statistics of the elevations within each census tract in a county are calculated to estimate the number of people living in areas below the storm surge level caused by a Category 3 storm. The population density of the census tract is assumed to be uniform throughout. Similar socio-economic variables to those used by Cutter are considered to find the total vulnerability. A rough estimate is that approximately 8 per cent of the Texas coastal population is living below the threshold elevation. This type of an index, with physiographic and demographic components, helps to identify the most vulnerable populations at a scale of census tracts, which is helpful for the local authorities for disaster preparedness and relief operations.