Comparison of Social Vulnerability and Flood Risks in Massachusetts

Abstract:

Climate and land use changes have led to increased frequency, intensity, and duration of extreme hydrological events, often unevenly impacting disadvantaged members of society. Specifically, in the Northeastern United States, the frequency of severe hydrological events such as flash floods, hurricanes, and storm surges have increased as have thermodynamic and dynamic atmospheric change. These extreme hydrological events pose a distinct risk to socially vulnerable communities that have limited ability to rebound from such events. Therefore, identifying vulnerable communities and assessing the severity of hydrological risk requires the coupled examination of biophysical risks and identification of socioeconomic factors limiting community resilience and responses. However, there are limited examples of this coupling in the Northeast. To address these knowledge gaps, we examined the spatial distribution of hydrological risks in Massachusetts according to hazard areas (100- and 500-year flood zones) delineated in the Flood Insurance Rate Maps developed by the Federal Emergency Management Agency. We selected four cities in Massachusetts (across 3 regions of the state) and paired these flood maps with the cities’ municipal political boundary, their census tract scale sociodemographic data revealed in their Massachusetts State Environmental Justice Indices (EJI), and their Centers for Disease Control Social Vulnerability Indices (SVI) developed at the census block group scales. The results of the study demonstrate that current hydrologic extremes are disproportionately contained within block groups of vulnerable populations (65% of 500 yr flood area; 34% of 100 yr flood area for Lawrence) as percentage of population in EJ groups increases from 70% (Worcester) to 100% (Lawrence). Furthermore, the increased detail provided in EJ block group delineation (as compared to SVI tract scale) provides increased understanding of potential zones at which to prioritize local interventions.