Upscaling shallow water models for overland ow using roughness formulations
Environmental Earth Sciences
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Özgen, I., Teuber, K., Simons, F., Liang, D., & Hinkelmann, R. (2015). Upscaling shallow water models for overland ow using roughness formulations. Environmental Earth Sciences https://doi.org/10.1007/s12665-015-4726-7
This study presents a novel roughness formulation to conceptually account for microtopography and compares it to four existing roughness models from literature. The aim is to increase the grid size for computational efficiency, while capturing subgrid scale effects with the roughness formulation to prevent the loss in accuracy associated with coarse grids. All roughness approaches are implemented in the Hydroinformatics Modeling System and compared with results of a high resolution shallow water model in three test cases: rainfall-runoff on an inclined plane with sinewave shaped microtopography, ow over an inclined plane with random microtopography and rainfall-runoff in a small natural catchment. Although the high resolution results can not be reproduced exactly by the coarse grid model, e.g. local details of ow processes can not be resolved, overall good agreement between the upscaled models and the high resolution model has been achieved. The proposed roughness formulation generally shows the best agreement of all compared models. It is further concluded that the accuracy increases with the number of calibration parameters available, however the calibration process becomes more difficult. Using coarser grids results in significant speedup in comparison with the high resolution simulation. In the presented test cases the speedup varies from 20 up to 2520, depending on the size and complexity of the test case and the difference in cell sizes.
upscaling, roughness formulation, shallow water equations, overland flow
The authors thank the Alexander von Humboldt-Foundation for the Humboldt Research Fellowship granted to Dr. Dongfang Liang.
External DOI: https://doi.org/10.1007/s12665-015-4726-7
This record's URL: https://www.repository.cam.ac.uk/handle/1810/249280