Sensitivity of hydrogeomorphological hazards in the Qinling Mountains, China

Investigations into hydrogeomorphological hazards in the Qinling Mountains were conducted by consideration of orographic characteristics and climatic fluctuations. Climatic-orographic-hydrologic processes in the Qinling Mountains were assessed through model simulation from proposed hydrodynamic gradient model and hydrological hazard index model combined with MM5 model (PSU/NCAR, 2005) and HEC-HMS/RAS (. USACE, 2008) model. Results show that climate change is key contributor to flood extreme events, and the Qinling Mountains has increased risk of rainstorm-flood extreme events. The hydrogeomorphological gradient has strong north-south gradient distribution due to orographic effects of the Qinling Mountains. Climate change impacts on hydrogeomorphological processes are dominated by short and severe rainstorms. High-frequency heavy rain regions are located in steep topographic gradients, such as the north-south valleys and windward slopes of higher elevations in the Qinling Mountains. The hydrogeomorphological consequences intensify the occurrence of localized extreme flash floods and accelerated erosion, altering flooding routing in the upper Hanjiang River basin. Flood routing is likely to be controlled by topographic rainfall for shorter periods (5-year and 10-year), and by climate change for longer periods (50-year and 100-year). Rainstorms and sediment gravity accumulation are the main causes of hazards.