An Operational Forecasting System for Flash Floods in Mountainous Areas in Taiwan

Yung-Ming Chen,Yi-Chiang Yu,Lee-Yaw Lin,Hung-Ju Shih,Wei-Bo Chen,Che-Hsin Liu,Chih-Hsin Chang,Wen-Ray Su

doi:10.3390/w11102100

Yung-Ming Chen, Yi-Chiang Yu + Show 6 more

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https://doi.org/10.3390/w11102100

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Abstract

Flash floods are different from common floods because they occur rapidly over short time scales, and they are considered to be one of the most devastating natural hazards worldwide. Mountainous areas with high population densities are particularly threatened by flash floods because steep slopes generate high flow velocities. Therefore, there is a great need to develop an operational forecasting system (OFS) for better flash flood prediction and warning in mountainous regions. This study developed an OFS through the integration of meteorological, hydrological, and hydrodynamic models. Airborne light detection and ranging (LiDAR) data were used to generate a digital elevation model (DEM). The OFS employs high-density and high-accuracy airborne LiDAR DEM data to simulate rapid water level rises and flooding as the result of intense rainfall within relatively small watersheds. The water levels and flood extent derived from the OFS are in agreement with the measured and surveyed data. The OFS has been adopted by the National Science and Technology Center for Disaster Reduction (NCDR) for forecasting flash floods every six hours in a mountainous floodplain in Taiwan. The 1D and 2D visualization of the OFS is performed via the National Center for Atmospheric Research Command Language (NCL).

Highlights

IntroductionRapid increases in riverine water levels (i.e., flash floods) can cause heavy casualties, especially in mountainous areas
Rapid increases in riverine water levels can cause heavy casualties, especially in mountainous areas
This study presents a multi-model integrated simulation scheme to construct an operational forecasting system (OFS) for flash flood emergency preparedness in two small mountainous watersheds in Taiwan

Summary

Introduction

Rapid increases in riverine water levels (i.e., flash floods) can cause heavy casualties, especially in mountainous areas. Floods that occur in mountainous watersheds are often flashy [1,2]. In contrast to common fluvial floods, the lead time for the early warning of flash floods in mountainous areas is generally very limited. The occurrences of flash floods are becoming increasingly frequent due to climate change and human actions [3], and flash floods in mountainous regions are more devastating than those in urban areas. When flash flood events occur in a small spatial scale watershed with a short time scale for the rapid production of surface runoff (e.g. intense rainfall or rainfall on highly saturated soils) in mountainous terrain. Many potential factors contribute to a flash flood, the main factor associated with riverine flash floods identified by Matsuda et al [4], based on data on flash flood disasters in Japan over

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