Changes in social vulnerability to flooding: a quasi-experimental analysis

In this study we estimate how flooded areas evolve on measures of social vulnerability over both the long and short term in Calgary, Canada. The first part of our analysis describes trends in indicators of social vulnerability across different levels of flood hazard over a 25-year period. The second part of our analysis uses a quasi-experimental study design to estimate short-term changes in social vulnerability in Calgary which may, in part, be related to the 2013 flood. We find that high flood hazard levels are generally associated with the lowest levels of social vulnerability, and that dwelling value has increased faster in high flood hazard areas than low flood hazard areas over the last two decades. The second part of our analysis indicates that relative to comparable non-flooded areas, flood-affected areas observed a 2.5 percent increase in postsecondary education level, a $37,000 reduction in median dwelling value, a 4.1% decrease in home ownership, a 2.9% increase in recent housing construction, a 2.6% increase in recent movers and a 1.6% decrease in the proportion of immigrants. Together, these findings suggest that in Calgary (1) over the long-term high flood hazard areas are generally comprised of lower vulnerability populations, increasing property wealth and higher income and (2) flood events may be associated with a short-term decline in social vulnerability.