Abstract. The characteristics of exposed built environments have a significant effect on debris flow impacts on buildings, but knowledge about their interactions is still limited. This paper presents a sensitivity analysis on the peak impact forces on a whole building resulting from the built environment parameters, including the orientation, opening scale of the target building, and azimuthal angle and distance of surrounding buildings. The impact forces were obtained from the monophasic viscous debris flow with a synthetic and simplified hydrograph using the FLOW-3D model, a computational fluid dynamics approach, verified through the physical modeling results. The results show that the surrounding buildings' properties have significant roles in determining the peak impact forces. A shielding effect or canalization effect, which reduces or increases impact forces, respectively, can be produced by changing the azimuth angle. A deflection wall for building protection is recommended according to the shielding effect. A narrowed flow path, determined by both the azimuth angle and distance, has a significant effect on the variation in impact forces. In addition, it is concluded that a splitting wedge should be designed following a criterion of avoiding the highest flow depth – the maximum approaching angle – appearing near the longest wall element. The protruding parts caused by changing the building's orientation contribute to increasing impact loads within a shielding area. A limited opening scale effect is observed on the whole building if there is sufficient time for material intrusion. The insights gained contribute to a better understanding of building vulnerability indicators and local migration design against debris flow hazard.

Abstract. The characteristics of exposed built environments have a significant effect on debris flow impacts on buildings, but knowledge about their interactions is still limited. This paper presents a sensitivity analysis on the overall peak impact forces on a building resulting from the built environment parameters, including the orientation, opening scale of the target building, and azimuthal angle and distance of surrounding buildings. The impact forces were obtained using the FLOW-3D model, a computational fluid dynamics approach, verified through the physical modeling results. The results show that the surrounding buildings’ properties have significant roles in determining the peak impact forces. A shielding effect or canalization effect, which reduce or increase impact forces, respectively, can be produced by changing the azimuth angle. A deflection wall for building protection is recommended according to the shielding effect. A narrowed flow path, determined by both the azimuth angle and distance, has a significant effect on the variation in impact forces. In addition, it is concluded that a splitting wedge should be designed following a criterion of avoiding the highest flow velocity – the smallest approaching angle – appearing near the longest wall element. The protruding parts caused by changing the building’s orientation contribute to increasing impact loads within a shielding area. A limited opening effect is observed on the whole building if there is sufficient time for material intrusion. The insights gained contribute to a better understanding of building vulnerability indicators and local migration design against debris flow hazard.

With complex and diverse ecosystem types and complete ecological elements such as mountains, rivers, forests, farmlands, lakes, grasslands, sand, and glaciers, the Ruoergai Prairie upstream of the Yellow River is an integral part of the Qinghai-Tibet Ecological barrier and a critical area for ensuring the ecological security of China. In the Ruoergai Prairie, climate change and human activities have led to grassland degradation, water and soil loss, and a shrinking forest area, which has highlighted the need for ecological restoration. Therefore, a comprehensive ecosystem evaluation is of great significance for ecosystem restoration. This study evaluated the ecosystem quality, ecosystem service function importance, ecological vulnerability, ecological protection importance, ecological resilience, and ecological landscape patterns of prairies, wetlands, and forests. The ecosystem quality of the study area was medium to good. The ecosystem service function of the study area with weak ecosystem resilience is important. However, the ecological landscape in the study area has been heavily degraded. Therefore, the protection and restoration of mountains, waters, forests, farmlands, lakes, grasslands, sand, and glaciers are needed.