Climatic Resilience of Mountainous Villages in Northern China: a Case of YongDingHe watershed

Climate change has led to a significant increase in the intensity and frequency of extreme meteorological events, resulting a substantial increase in flood risk for a large part of China's monsoon region territory. In the north of China, rainfall is highly concentrated temporally and spatially, posing significant flood risks to numerous villages in mountainous watersheds. The SWMM model was coupled with the HEC-RAS two-dimensional hydrodynamic model to simulate the flood inundation levels of 38 villages in YongDingHe watershed under extreme precipitation conditions.

The results indicate: (1) In terms of overall flood risk, villages located downstream of the Qingshui River and at the exit of the YongDingHe River gorge have higher flood risks, and under the three future SSPs scenarios, peak river flow, the number of flooded villages, flooded area, and inundation depth all significantly increase. (2) In different SSPs scenarios, 40% to 72% of medium-sized villages will be flooded under the 100-year return period, while 35.2% of small settlements have no flood risk. (3) The risk of village inundation is sensitive with the distance from water bodies, while under the 100-year return period in the SSP126, SSP245, and SSP585 scenarios, the inundation area of water-distant villages is 56.8%, 54%, and 60.9% smaller than that of water- proximate villages, respectively..

Villages with relatively high overall risks should build intercepting ditches and slope vegetation buffer zones on slopes to intercept slope runoff and slow down the flow speed of floods. Ecological ponds should be constructed in low-lying areas to temporarily store floodwater. Dry stone check dams should be built in mountain stream valleys to reduce the water flow speed and disperse the flood energy. The layout of land use in and around the villages should be optimized and adjusted, and flexible land use functions should be arranged in low-lying areas.