Abstract
An operational two-dimensional real-time flood forecasting system has been developed in Taiwan to prevent urban inundation. This system takes an hour to come up with forecasts for the next three hours, and the resolution of the forecasts is 40 × 40 m. This study used a large urban area of 126 km2 in downtown Taichung City for the case study and adopted the active-cell and multi-grid methods to meet the target by computing from data of a 12-h rainfall within one hour at 20 m × 20 m spatial resolution to provide faster forecasting and more hours for flood preparation. With the active-cell method, the Central Processing Unit (CPU) time was reduced by 65.04% from 659 m 29 s to 230 m 33 s under the 200-year return period storm. Further, with multi-grid methods, the CUP time was reduced by 73.98% from 230 m 33 s to 60 m 0 s. In general, the computing time of this model has been reduced 11-fold. The error validation coefficients of inundation areas were between 89.39~97.45% with an average error of depth between 1.06~3.22 cm.
Highlights
Many countries have developed flood forecasting systems for flood prevention, such as the UK [1], Finland [2], Australia [3], Sweden [4], United States [5], Mekong River Commission [6], and so on
In Taiwan, the Water Resources Agency has developed flood forecasting systems using the structure of the Delft-FEWS (Flood Early Warning System) platform
Domain decomposition is a common algorithm for parallelization computation; the into many subcatchments, the flow usually crosses over between subcatchment and its neighboring algorithm is limited to simulation areas with enormous high-resolution Digital Elevation Model (DEM), especially in urban subcatchments during storms and water typhoons
Summary
Many countries have developed flood forecasting systems for flood prevention, such as the UK [1], Finland [2], Australia [3], Sweden [4], United States [5], Mekong River Commission [6], and so on. Most of the flood forecasting systems, using a one-dimensional model for the computation, cannot accurately simulate flow in urban areas [9]. In 2016, a two-dimensional real-time flood forecasting system was developed to prevent urban inundation in Taiwan This system adopts the Delft-FEWS platform to integrate the quantitative precipitation forecasts form the Central Weather Bureau and the SOBEK model. Domain decomposition is a common algorithm for parallelization computation; the into many subcatchments, the flow usually crosses over between subcatchment and its neighboring algorithm is limited to simulation areas with enormous high-resolution DEMs, especially in urban subcatchments during storms and water typhoons. The model real-time flood forecasting system in Taichung City has been developed, and the resolution of the simulation of the entire urban area results in the increase of computation time when using higher forecasts is 40 × 40 m. Study is to compute the model from a 12-h rainfall within one hour at 20 m × 20 m spatial resolution to provide faster forecasting and more hours for flood preparation
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