Abstract
Based on the flood area hydrodynamic model, this paper backs the analysis of the risk warning point of the Mayang Stream in the typical flood process, to determine the disaster-caused critical precipitation and the corresponding flood risk map at different depths of submergence. The result is used as the mountain torrent disaster monitoring and warning indicators and risk assessment of the Mayang Stream. Then based on the flood risk warning service system of small and middle rivers of Fujian Province, the risk warning service of mountain torrent disaster is developed during the impact time of Meranti in 2016. After the process of typhoon, the mountain torrent caused by Meranti was back analyzed by using the decided flood area model, then compared with the results of filed investigation to verify the accuracy of the disaster-caused critical precipitation forecast and the effect of monitoring and early warning services. The result shows that the cause of Mayang Stream’s mountain torrent disaster of the typhoon Meranti is the heavy rainfall and the strong wind. The highest mountain torrent disaster was forecasted by the refine precipitation based on the disaster-caused critical rainfall of the Mayang Stream. The simulated flood scenarios and the field trip’s results were basically matched in upstream and not matched in the downstream. The post-mountain simulation assessment also showed that the flood inundation range basically matched with reality, but the flood process was biased. The reason was that in addition to the differences between the surface rainfall forecast and the real situation, many actual situations cannot be ignored. For example, Meranti caused serious damage to trees, increased river blockages, resulting in changes in flood inundation time and depth, affecting the flood process. It showed the tourism development would cause the river way blocking and increase the risk of flood. In order to prevent and reduce the flood disasters accurately and effectively, the flood risk forecast and the disaster-caused facts should be considered at the same time.
Highlights
China is a mountainous country, and the hilly area covers about two-thirds of the country’s land area
Based on the flood area hydrodynamic model, this paper backs the analysis of the risk warning point of the Mayang Stream in the typical flood process, to determine the disaster-caused critical precipitation and the corresponding flood risk map at different depths of submergence
Based on the flood risk warning service system of small and middle rivers of Fujian Province, the risk warning service of mountain torrent disaster is developed during the impact time of Meranti in 2016
Summary
China is a mountainous country, and the hilly area covers about two-thirds of the country’s land area It is affected by many factors such as special natural geographical environment, extreme severe weather and economic and social activities. This paper hopes that there will be another severe mountain flooding case that occurred after the typhoon Meranti landing in 2016 affected Fujian and Mayang Stream in Changtai County. A field survey was conducted to compare and analyze the weather risk warning service for mountain torrents based on the achievements of critical floods and the “System” for the prevention of floods, to test the accuracy of the critical rainfall caused by flash floods and the effectiveness of monitoring and early warning services. Further analysis of the causes of the occurrence of rare flash floods in Mayang Stream laid the foundation for improving the capacity of meteorological services for mountain torrents
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