Author(s): Wei Huang; Zhixian Cao; Paul Carling; Gareth Pender
Linked Author(s): Wei Huang
Keywords: Glacier dam-break flood; Well-balanced; 2D hydrodynamic model; OpenMP
Abstract: One of the largest known megafloods due to glacier dam-break is that occurred during Late Quaternary in Altai Mountains, Southern Siberia. Hydrodynamic modelling is one of the viable approaches to enhancing the understanding of the ancient flood due to glacier dam-break. A well-balanced two dimensional hydrodynamic model, which can properly capture shock waves, cope with rugged bed topography and handle drying and wetting interface transition, is deployed to reconstruct the flood on the area which involves Chuya River, Katun River and Uimon Basin. The computational area is over 9460 km2 and about 3. 784×106 cells are involved as 50 m × 50 m mesh is used. In addition, the duration of the flood is 48 hours. Thus long computational time is required. To enhance the efficiency of the model, the OpenMP (Open Multiprocessing) technique is adopted to parallelize the code. The full process of the flood wave is well reproduced with specified discharge hydrographs at the dam site. The computed maximum stage profile agrees with field data rather well. The shape and peak value of the inlet discharge hydrograph at the dam site may influence the process of the flood. Moreover, the Manning roughness in relation to bed friction is also a major source of uncertainty. A sensitivity analysis of the impacts of the aforementioned three factors is carried out. It is shown that the influences of Manning roughness and shape of the inlet discharge hydrograph are marginal compared to that of the value of peak discharge. Besides the understanding of the spatial and temporal hydraulics of the megaflood, the implications of sediment transport and geomorphology during the flood are presented.
Year: 2013