Expert links deadly mudslide in SW China to shifting rainfall patterns and geohazard risks

Saturday's deadly mudslide triggered by torrential rains has killed at least 10 people and 17 others are missing in Ridi Village of Kangding City located in Ganzi Zang Autonomous Prefecture in southwest China's Sichuan Province. The village, situated in a valley surrounded by high mountains, was heavily affected by the disaster.

The mudslide can be attributed to rainfall moving west away from the traditional rainfall areas due to the changes in weather patterns, according to Professor Wang Yunsheng from the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection at Chengdu University of Technology, who is currently participating in the rescue mission following the mudslide.

"The primary factors influencing the global climate have shifted from El Nino to La Nina, resulting in noticeable changes in weather patterns," said Wang. "In China, there has been a noticeable shift in heavy rainfall patterns towards the north and west. Areas that were previously drought-stricken are now experiencing increased rainfall."

"This year, unprecedented heavy rains have occurred north of the Qinling Mountains. In Sichuan, heavy rains, which typically occurred in the basins, have now moved westward, as is the case with the Ganzi Zang Autonomous Prefecture," Wang told CGTN.

According to Wang, the area is prone to earthquakes and natural disasters like landslides and mudslides due to its geological volatility. He explained that the disaster site is located in the Hengduan Mountains, a range in southwest China connecting the Qinghai-Xizang Plateau and the Yunnan-Guizhou Plateau. The region's history of earthquakes and structural changes, combined with steep slopes and elevation differences, leads to strong and fast-moving debris flows.

Recent high temperatures have exacerbated the situation, with continuous rain and melting ice causing mud and rocks to wash down the unstable slopes, resulting in the deadly mudslide.

"I went to the site and found the water freezing cold. The rainwater alone wouldn't be that cold without ice and snow," said Wang.

Besides, the valley's 10.5-kilometer stretch descends from around 5,700 meters to about 1,700 meters, creating a 4,000-meter drop. This steep gradient not only intensified the mudslide but also made weather forecasting more difficult, Wang noted.

"The weather is different up and down the mountain. People down the mountain couldn't detect the torrential rain at the top and thus didn't know that disaster was already happening up there," he said.

"In the future, we should install more rain gauges, expand the observation area, and enhance weather monitoring, especially in regions with large altitude differences."

The mudslide has blocked the G318 National Highway, and the rising water levels in the valley hampered rescue efforts.

"The first step was to redirect the water flow back into the ditch and conduct search and rescue operations on dry land, which has now been completed," Wang said. "G318 National Highway is close to being cleared and will be open to traffic on Monday. The next step is to continue assessing the safety of residential areas."

The local authorities swiftly evacuated 939 residents and set up four temporary shelters to accommodate those displaced by the disaster. According to reports, essential supplies, such as toothbrushes and toiletries, have been provided to the displaced villagers, and bottled water and instant noodles are plentiful.