Partition of one-dimensional river flood routing uncertainty due to boundary conditions and riverbed roughness

Abstract

The partition of flood routing uncertainties from multiple sources provides a foundation for managing flood risks. This paper develops a partition approach for the one-dimensional river flood routing uncertainty due to boundary conditions (upstream inflow hydrograph and downstream stage hydrograph) and riverbed roughness. A theoretical derivation based on the Monte Carlo method is presented using a one-dimensional hydrodynamic model. The developed approach is successfully applied to a real-world case of the Xunjiang River in China. The results indicate the following: (1) each uncertainty source leads to unique effects on flood routing, and the uncertainty contribution ratio varies significantly with both time and space, providing evidences for identifying the dominant uncertainty sources; (2) the uncertainty of the simulated discharge is most influenced by the boundary conditions whereas the simulated water stage is most influenced by the riverbed roughness; and (3) the highly coupled uncertainty propagation is hardly affected by the flood pattern, as well as the probability distribution of uncertainty source, but it is significantly affected by the river morphology. The developed approach can effectively partition the uncertainty effects of the boundary conditions and riverbed roughness without explicating their interactions. And the uncertainty partition of flood routing is useful for risky decision making in flood management.