Loss of Life Estimation Due to Flash Floods in Residential Areas using a Regional Model

Abstract

Flood is a severe natural disaster which causes major damages in most regions including in Iran. Loss of human lives as a consequence of flash flood has not been sufficiently studied despite its high annual rate. Review of related literature indicates relatively low accuracy of available global relationships for estimating loss of life due to flash floods. As a result, regional equations dealing with loss of life estimation relying on all effective hydraulic and evacuation variables is a way forward. In this study, hydraulic variables, such as depth, velocity and rise rate, and evacuation parameters, including available time for evacuation and fraction of people evacuated, were adopted to develop a regional loss of life equation in residential areas of Kan watershed case study, Tehran, Iran, using a calibrated 2DHEC-RAS model. Different number of fatalities in downstream and upstream villages revealed the importance of evacuation time when an early flood warning system is operational. Comparison of the proposed regional equation with available global equations showed that the proposed equation provides more accurate estimation of the number of fatalities in the study area. Regarding the estimated mortality, a local sensitivity analysis performed on the developed equation showed the importance of flood depth to evacuation time ratio, water rising rate and flow velocity, respectively.