Vulnerability Situations associated with Flash Flood Casualties in the United States

Abstract:

In the United States (U.S.) flash flooding (FF hereafter) is one of the leading cause of weather-related deaths. Because FF events can be distinguished from riverine floods by their fast response to rainfall and resulting impacts signature, analyzing FF-specific impact datasets seems a good way to identify the juxtaposition of social and physical circumstances leading to those impacts. This communication focuses on conceptual and methodological developments allowing testing hypotheses on FF-specific vulnerability factors through the analysis of human impact datasets. We hypothesize that the intersection of the spatio-temporal context of the FF phenomena with the distribution of people and their characteristics across space and time reveals various paths of vulnerability through the expression of different accidents’ circumstances (i.e., vehicle-related, inside buildings, open-air, campsites). We argue that vulnerability and the resulting impacts vary dynamically throughout the day according to the location/situation under concern.

In order to test FF-specific contextual vulnerability factors at the scale of the continental US, 1075 fatalities reported between 1996 and 2014 in the Storm Data publication of the U.S. National Climatic Data Center (NCDC) are analyzed to statistically explore the timing, the duration and the location of the FF event, and the age and gender of the victims and the circumstance (i.e. location/activity) of their death. In this objective, a re-classification of the individual fatality circumstances and a discretization of the time in qualitative time-steps are performed to obtain possible trends and patterns in the occurrence of fatalities in certain circumstances and time (e.g., day vs night). The findings highlight the importance of situation-specific assessment of FF fatalities to guide the development of FF-specific vulnerability and impacts prediction modeling. Such analysis can provide valuable knowledge when the National Weather Service issues FF warning and emergencies. This is because targeted warnings can be communicated when we can relate the location of risky incidents in space (e.g., roads, campsites, mobile homes) with specific vulnerable groups (e.g., certain age groups, gender).