Climate warming increases the risk of flooding from rain rain events in alpine Asia, research finds

A recent study led by Professor Chen Yanning of the New Jiang Institute of Ecology and Geography at the Chinese Academy of Sciences found that climate warming has increased flood risk from rainline (ROS) events in Alpine Asia. This study, published in NPJ Climate and Atmospheric Science, analyzed the distribution, causes, and flood risk of ROS events.

ROS events where rainfall interacts with snow are common in high altitude areas and can lead to flooding and avalanches.

In this study, the researchers showed that alpine Asia experiences an average of 22.4 ROS days per year, with the Ganges River Basin having the highest frequency at 45.8 days. Most ROS events occur in winter, two-thirds of the region, particularly along major rivers such as Yangtze and Amu Darya. Spring accounts for about 25% of these events, mainly near Lake Barkas, summer (13.5%) events are mainly in high altitude areas, while autumn events are rare.

The average daily ROS intensity is 5.29 mm, driven primarily by rainfall (65.9%) and snow melt (34.1%). The number of ROS days has decreased by 0.031 days per year, but the timing of ROS events is faster and the intensity is weaker. At lower altitudes, snow days promote a reduction in reduced ROS events, whereas at higher altitudes, increased rainfall days contribute to more frequent ROS occurrences.

This study highlights the threat of ROS flood events (Rosflood), which can cause rapid snow thawing. Areas with higher snowpacks are 2.83 times higher than areas with lower snow melt rates. The Ganges River and the Illawady Basin are identified as zones at high risk of ROS flooding, reaching daily intensity up to 24.87 mm. High-risk areas are usually located at elevations of 3.0-4.5 km.

These findings highlight the importance of understanding ROS patterns and strengthening flood prevention and disaster management in mountainous regions.