Abstract
The China flash flood investigation and evaluation database (CFFIED) covers important information needed for China’s flash flood warning. This paper uses a statistical induction method, inference formula method and standardized unit hydrograph method to explore its principle, characteristics, and key steps. Then based on the field investigation and the latest data on the flash flood, the Hunjiang District in northeastern China was selected as the research area. Firstly, three typical riverside villages, Xiangmo-1 and Sanchahe-3, Shangqing-4, were screened, and the flash flood warning indicators (e.g., water level, flow rate, critical rainfall) in the CFFIED were updated. Then, the maximum error of the flood peak, estimated by the inference formula method and the water level flow relationship method, is only 10.6%, which indicates that the predicted flood peak flow has high credibility and can check and identify the early warning index; the Manning formula is more accurate in calculating the water level flow relationship. However, the calculated ratio is lower and the roughness is higher, and the flow is smaller under the same water level. Finally, the updated flash flood warning indicators were obtained in the Hunjiang District, which improves the accuracy of the flash flood warning, and provides a reference for updating the early warning indicators in other areas.
Highlights
Extreme torrential rains are known for triggering devastating flash floods in various regions of the world, especially in small basins characterized by complex terrain [1]
The flash flood is caused by short-term torrential rains, calculated by combining the rainstorm diminishing index n and the storm formula with the 24-h design rainfall, where n is calculated from the relationship between the average rainfall and the corresponding diachronic point over the years, and the conversion from point rainfall to surface rainfall is calculated using the point reduction factor
Rtij is the maximum rainfall of the j-th flash flood at the i-th rain station in t period, and the smallest of the N statistical values is initially considered as the critical rainfall, and the calculation formula is as follows: Rtic = Min( Rtij ), ( j = 1, 2, 3, · · ·, N )
Summary
Extreme torrential rains (i.e., high intensity and short duration) are known for triggering devastating flash floods in various regions of the world, especially in small basins (hundreds of square kilometers or less) characterized by complex terrain [1]. The real-time flash flood warning methods are mainly based on a distributed hydrological model or adopting dynamic critical rainfall warning methods abroad, which requires special support platform for complex calculation. The Hunjiang District of Northeast China is taken as a typical study area, and the flash flood warning indicators are checked and verified based on statistical induction and hydrological hydraulic methods. Water 2019, 11, x FOR PEER REVIEW and analyze the peak flow, disaster flow and total flood volume, (iii) to check and verify the early warning indicators of rainfall, results ofverify whichthewill form a scientific basisoffor the flash flood flow and total flood volume,. Of which will form a scientific basis for the flash flood warning service of the information society
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