Modelling debris flows to enhance disaster risk management in the Zhouqu region, Gansu China

The Zhouqu area of the Bailong River Basin (Z-BRB), Gansu Province, China is an area covering some 400 km² and is characterised by a dynamic natural environment where lives, livelihoods and critical infrastructures are at risk from flooding and various mass movements in rock and soil. The Z-BRB area is characterized by a neo-tectonically active environment with high topographic relief and elevations ranging from 1200 m to more than 4000 m. Mass movements include large earthflows (several are more than 3 km in length), rock falls and debris flows, and these play a prominent role in shaping this landscape. The area is developing rapidly, going through major expansions of urban communities and infrastructure networks. To achieve long-term sustainable development, it is urgently needed to identify the spatial and temporal patterns of multiple, and often interacting geohazards. Dynamic terrains, such as in the Z-BRB area, evolve over time. The current state of the landscape is adjusting to a range of influences that can be thought of as a nested hierarchy of processes acting over different scales, both in time and space. To gain an improved insight into this state of the landscape it is important to unpack this hierarchy, identify interactions between processes and identify their magnitudes and rates of change. By combining geomorphological mapping and numerical modelling of landslides and tying it together with an understanding of the different timelines of the various processes our goal is to develop a risk management framework for the Z-BRB area. Currently the research is focused on modelling of debris flows using the numerical model HiPIMS, which couples shallow water and sediment transport equations. HiPIMS has been calibrated against a physical experiment and the 2010 Zhouqu disaster. This enhances our confidence that the model can be applied in similar catchments elsewhere in the Z-BRB. The aim of the modelling is to identify catchments at risk of debris flows, investigate how climate change, i.e.  higher precipitation and more extreme rainfall events, will affect the catchments, and how mitigation measures such as check dams will cope with an increase in magnitude and frequency of debris flows/mobility of earthflows.