Social Vulnerability Analysis

 

Introduction

An operational definition for social vulnerability in this study will be the relative exposure of the population for a given risk factor as a percentage of the total population. The social vulnerability index will be constructed by taking the sum of each of these percentage points and dividing them by the total number of risk factors. The index does not consider post-tsunami vulnerabilities such as ability to recover or the need for more long-term sheltering as this is beyond the scope of the study. This method has been adapted based on a 2013 report by the USGS (United States Geological Survey 2013) which argues that inferring actual causal relationships between risk factors and tsunami mortality and injury would invite undue speculation. This method is descriptive and avoids misrepresenting vulnerability through unsubstantiated and unduly subjective factor weightings.

 

Data Overview

Data for the vulnerability index were sourced from 2006 Census data from Statistics Canada (Statistics Canada 2007) using all available dissemination areas for the Alberni-Clayoquot census division. Each dissemination area (DA) was checked for a corresponding DA polygon within the ArcGIS project and superfluous data was discarded so that each DA polygon had only one corresponding row of census data. Populations for each DA ranged between 400 and 600 with some outliers.

Data analysis happened within an Excel spreadsheet and the final vulnerability values were manually added to the ArcGIS project. Port Alberni has several Indian Reserves (IRs) that are not covered by the dataset available and have not been included in the analysis. The vulnerability index itself is calculated for each DA as follows:

 

Port Alberni

 

For example, if 30 out of 300 people of a DA meet a specified criterion, that factor for the DA will have a value of 10. For another criterion, if 3 people out of 300 match the criteria, that factor for the DA will have a value of 1. The sum of the percentage points (11) is divided by the total number of risk factors (2) and the DA would have a score of 5.5 or 0.055. This value is now normalised and can be compared against other DAs that have been calculated in the same way.

 

Risk Factors

 

The final output map appeared as follows:

Port Alberni

The social vulnerability map highlights areas near the east slopes along with high risk areas directly north of the inlet and along the Somas River. An Indian Reservation lies adjacent to the the high-risk DA in the north and erroneously has a 'low' vulnerability associated.

 

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