Classification of extreme precipitation events and associated flood risk in central China

Flood disasters, generally triggered by extreme precipitation events (EPEs), pose serious threats to life and property in China, accounting for about 37.2 percent of economic losses and about 11.7 percent of the death toll of all meteorological disasters. Mesoscale weather systems, frequently occurring and inducing persistent precipitation events, are largely responsible for continuous flood peaks and severe floods. Meanwhile, the combined effect of rapid urbanization, river network degradation and EPEs has an adverse effect on urban hydrological processes, particularly in terms of increasing urban flood risk and causing serious urban flooding losses. A recent study reveals the characteristics of EPEs and their flood risk in the region.

To investigate several questions: Have the most frequent and strongest EPEs overlapped with the area of rapid urbanization over the Yangtze-Huaihe River Valley (YHRV)? Has there been a common thermodynamic mechanism and similar propagation trajectories for different EPE types? And how is it possible to identify small-scale and high-intensity flood risks due to EPEs in areas of rapid urbanization and degrading river networks? Scientists from Nanjing University of Information Science and Technology and Jiangsu Climate Center carried out an attribution study by performing statistical percentile method, potential vorticity diagnosis, and a set of numerical experiments with different torrential flooding.

"Persistent EPEs are largely responsible for continuous flood peaks and severe floods." says Dr. Du Yin from Nanjing University of Information Science and Technology." There is an urgent need to clarify the occurrence and evolution mechanism and extend the forecast valid time of EPEs for scientific decision-making by government relating to disaster prevention and mitigation."

"In the RCP6.0 (RCP8.5) scenario, the built-up area increases at a rate of about 10.41 km2 (10yr)-1 (24.67 km2 (10yr)-1) from 2010 to 2100, and the area of high flood risk correspondingly increases from 3.86 km2(3.86 km2) to 9.00 km2(13.51 km2). Areas of high flood risk are mainly located at Chishan Lake in Jurong, Lukou International Airport in Nanjing, Dongshan in Jiangning District, Lishui District and other low-lying areas." predicts Dr. DU." The accurate simulation of flood scenarios can help reduce losses due to torrential flooding and improve early warnings, evacuation planning and risk analysis. More attention should be paid to the projected high flood risk because of the concentrated population, industrial zones and social wealth throughout metropolitan area."

More information:
Zhiqing Xie et al, Classification of yearly extreme precipitation events and associated flood risk in the Yangtze-Huaihe River Valley, Science China Earth Sciences (2018). DOI: 10.1007/s11430-017-9212-8

Provided by Science China Press