Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2016-620
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
13 Feb 2017
Review status
This discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
Impacts of spatial resolution and representation of flow connectivity on large-scale simulation of floods
Cherry May R. Mateo1,2, Dai Yamazaki3, Hyungjun Kim2, Adisorn Champathong4, Jai Vaze1, and Taikan Oki1 1CSIRO Land and Water, ACT, 2601 Australia
2Institute of Industrial Science, The University of Tokyo, Tokyo, 153-8505 Japan
3Department of Integrated Climate Change Projection Research, Japan Agency for Marine-Earth Science and Technology, Yokohama, 236-0001 Japan
4Royal Irrigation Department, Bangkok, 10300 Thailand
Abstract. Global-scale River Models (GRMs) are core tools for providing consistent estimates of global flood hazard, especially in data-scarce regions. Due to former limitations in computational power and input datasets, most GRMs have been developed to use simplified representation of flow physics and run at coarse spatial resolutions. With increasing computational power and improved datasets, the application of GRMs to finer resolutions is becoming a reality. To support development in this direction, the suitability of GRMs for application to finer resolutions needs to be assessed. This study investigates the impacts of spatial resolution and flow connectivity representation on the predictive capability of a GRM, CaMa-Flood, in simulating the 2011 extreme flood in Thailand. Analyses show that when single downstream connectivity (SDC) is assumed, simulation results deteriorate with finer spatial resolution; Nash–Sutcliffe Efficiency coefficient decreased by more than 35 % between simulation results at 10 km resolution and 1 km resolution. When multiple downstream connectivity (MDC) is represented, simulation results slightly improve with finer spatial resolution. The SDC simulations result in excessive backflows on very flat floodplains due to the restrictive flow directions in finer resolutions. MDC channels attenuated these effects by maintaining flow connectivity and flow capacity between floodplains in varying spatial resolutions. While a regional-scale flood was chosen as a test case, these findings are universal and can be extended to global-scale simulations. These results demonstrate that a GRM can be used for higher resolution simulations of large-scale floods, provided that MDC in rivers and floodplains is adequately represented in the model structure.

Citation: Mateo, C. M. R., Yamazaki, D., Kim, H., Champathong, A., Vaze, J., and Oki, T.: Impacts of spatial resolution and representation of flow connectivity on large-scale simulation of floods, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-620, in review, 2017.
Cherry May R. Mateo et al.
Cherry May R. Mateo et al.
Cherry May R. Mateo et al.

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Short summary
Providing large-scale (regional/global) simulation of floods at fine spatial resolution is necessary to provide consistent estimates of hazards, especially in data-scarce regions; but it is difficult due to computational constraints. We assessed the capability of an advanced global-scale river model to simulate an extreme flood at fine resolution. We found that when multiple flow connections in rivers are represented, the model can provide reliable fine-resolution predictions of flood inundation.
Providing large-scale (regional/global) simulation of floods at fine spatial resolution is...
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