Abstract
There has been an increase in the occurrence of sudden local flooding of great volume and short duration caused by heavy or excessive rainfall intensity over a small area, which presents the greatest potential danger threat to the natural environment, human life, public health and property, etc. Such flash floods have rapid runoff and debris flow that rises quickly with little or no advance warning to prevent flood damage. This study develops a flash flood index through the average of the same scale relative severity factors quantifying characteristics of hydrographs generated from a rainfall-runoff model for the long-term observed rainfall data in a small ungauged study basin, and presents regression equations between rainfall characteristics and the flash flood index. The aim of this study is to develop flash flood index-duration-frequency relation curves by combining the rainfall intensity-duration-frequency relation and the flash flood index from probability rainfall data in order to evaluate vulnerability to extreme flash floods in design storms. This study is an initial effort to quantify the flash flood severity of design storms for both existing and planned flood control facilities to cope with residual flood risks due to extreme flash floods that have ocurred frequently in recent years.
Highlights
A flash flood is local flooding of great volume and short duration
The rapid runoff associated with debris flow has inundated some watershed areas and the river flow altered by debris flow has resulted in some flood damage such as bank erosion and bridge collapses, as reported in the annual natural disaster bulletin [1]
This study has provided flash flood index-duration-frequency (FI-D-F) relation curves developed from rainfall intensity-duration-frequency (I-D-F) relations for the use of evaluating vulnerability to extreme flood conditions in a design storm in order to establish disaster countermeasures for residual flood risk in both existing and planned flood control facilities
Summary
A flash flood is local flooding of great volume and short duration. Such sudden local floods have occured quite frequently in recent years due to heavy or excessive rainfall in a short period of time over a small area. A rapid local flood poses the greatest potential danger threat to human life, public health and property, the natural environment and ecosystems, water and other natural resources, etc. Such types of dangerous flood damage constitute national-wide natural disasters, the structural and non-structural alternative plans for flood mitigation have been mainly carried out for large basins in
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