A data-driven analysis of flash flood hazard, fatalities, and damages over the CONUS during 1996–2017

Abstract

Flash floods are among the most disastrous natural hazards worldwide because of their rapid onset that limits effective emergency response and management. Understanding the spatiotemporal characteristics of flash floods can help emergency managers and stakeholders in devising solutions to mitigate the associated risks and damages. In this study, a data-driven approach is employed to characterize flash flood hazard across the contiguous United States (CONUS). The National Weather Service (NWS) Storm Events database is utilized, and a total of 74,814 flash flood events are assessed during 1996–2017. The frequency, duration, property damages, and fatalities of flash floods are investigated across spatial domains (i.e. county, state, regional, and entire CONUS) and multiple temporal scales (i.e. annual, seasonal, monthly, and diurnal). Results indicate that flash flood frequency has slightly increased over the CONUS in the past 22 years, and the property damages have substantially raised. Flash floods are found to be more frequent in summer and less frequent but longer in winter. Our analyses indicate distinct regional patterns for duration of median versus extreme flash floods. In addition, the diurnal distribution of flash floods indicate that they are more likely to initiate in the evening and terminate around midnight. The average duration of flash floods in the past 22 years has been about 3.5 h, yet in some rare cases, they persisted for about two days. The findings of this study can shed light on flash flood hazard across the CONUS, which can be useful for mitigating flash flood risks.