Evaluation of county-level riverine flood vulnerability of agricultural populations in the Potomac River Watershed

Floods are one of the most destructive natural hazards causing considerable economic losses throughout the world. Among several economic activities impacted by flooding, the agriculture sector is particularly vulnerable to this hazard, requiring a good comprehension of drivers of flood risk to manage it efficiently. In this research, an integrated vulnerability assessment framework, combining a flood hazard and a comprehensive social vulnerability assessment tool is presented to introduce a Flood Socio-Economic Vulnerability Index (FSOEVI) for agricultural populations. The Federal Emergency Management Agency(FEMA) 100-year riverine flood depth grid is coupled with an agricultural damage estimation approach adapted to allow combination between the method proposed by HAZUS-MH and a Social Vulnerability Index(SOVI) in a county based level assessment. Since agricultural damage estimation function uses the growth stage of crops as a daily variable for different types of crops, 365 scenarios with different flood exposure and FSOEVI are calculated. The Hazard of Place model is implemented to define SOVI levels with county-based assessment both in the U.S. and in the Potomac River Watershed (PRW) by combining 13 agricultural vulnerability parameters using the Principal Component Analysis (PCA) method. Before evaluation of SOVI levels in the PRW, county based comparative analysis of social vulnerability within the U.S is conducted to explore broad scale distribution of vulnerabilities and compare those of counties located within the PRW with other counties in rest of the country with same parameters. As a result of comparative analysis, while counties in the PRW have less vulnerable populations, counties in Arizona, Texas and Mississippi states are more vulnerable. With the replication of the SOVI methodology within the PRW, six different counties stood out as those with the most vulnerable agricultural population. The spatial distribution of FSOEVI for extreme and average conditions for all the 365 days are presented along with the monthly average of damage from 100-year flood. It is worthwhile to mention that the method presented in this study can potentially be replicated over the country, thus helping to support decisions towards the mitigation of natural hazards and protection of vulnerable populations.