Application of a lower-fidelity surrogate hydraulic model for historic flood reconstruction

Abstract

Two dimensional hydraulic models are useful to reconstruct maximum discharges and uncertainties of historic flood events. Since many model runs are needed to include the effects of uncertain input parameters, a sophisticated 2D model is not applicable due to computational time. Therefore, this papers studies whether a lower-fidelity model can be used instead. The presented methodological framework shows that a 1D-2D coupled model is capable of simulating maximum discharges with high accuracy in only a fraction of the calculation time needed for the high-fidelity model. Therefore, the lower-fidelity model is used to perform the sensitivity analysis. Multiple Linear Regression analysis and the computation of the Sobol' indices are used to apportion the model output variance to the most influential input parameters. We used the 1926 flood of the Rhine river as a case study and found that the roughness of grassland areas was by far the most influential parameter.

Historic Flood Reconstruction With the Use of an Artificial Neural Network

“…Only bed levels of the main channel and floodplains were uncertain caused by the interpolation of the measured cross sections (section 2.2). However, Bomers et al (2019c) found that uncertainties in the floodplain bed levels and main channel bed levels only have a small effect on the maximum discharges throughout the model domain. This justifies to neglect these uncertainties.…”

Hydraulic modelling approaches to decrease uncertainty in flood frequency relations

“…Since the cross sections had an interval of one kilometer, the accuracy near the bifurcation points of the Rhine river branches was not sucient to correctly simulate the discharge partitioning along the Dutch Rhine river branches. Therefore, the DEM at the locations of the bifurcation points is replaced by the 1926 DEM which was available from previous work (Bomers et al, 2019a).…”

Consequences of dike breaches and dike overflow in a bifurcating river system

“…However, many studies showed the applicability of a 1D-2D coupled model (e.g. Bomers et al 2019a;Domeneghetti et al 2013) and of the diffusive wave equations for flood modelling purposes (e.g. Moya Quiroga et al 2016;Moussa and Bocquillon 2009;Leandro et al 2014).…”

“…Such inundation patterns are possible in almost any deltaic areas (e.g. Lower Mississippi river and Atchafalaya river (Coleman et al 1998), the Mekong delta (Triet et al 2017) and the Rhine delta (Bomers et al 2018;Klerk et al 2014)).…”