Abstract
Abstract Sensitivity analysis is a commonly used technique in hydrological modeling for different purposes, including identifying the influential parameters and ranking them. This paper proposes a simplified sensitivity analysis approach by applying the Taguchi design and the ANOVA technique to 2D hydrodynamic flood simulations, which are computationally intensive. This approach offers an effective and practical way to rank the influencing parameters, quantify the contribution of each parameter to the variability of the outputs, and investigate the possible interaction between the input parameters. A number of 2D flood simulations have been carried out using the proposed combinations by Taguchi (L27 and L9 orthogonal arrays) to investigate the influence of four key input parameters, namely mesh size, runoff coefficient, roughness coefficient, and precipitation intensity. The results indicate that the methodology is adequate for sensitivity analysis, and that the precipitation intensity is the dominant parameter. Furthermore, the model calibration based on local variables (cross-sectional water level) can be inaccurate to simulate global variables (flooded area).
Highlights
In hydrologic modeling, the use of 2D hydrodynamic models is common in applications like floods or water quality assessment (e.g., Yu & Lane 2006; Park et al 2014; Zischg et al 2018)
Namely local water level and total flooded area, were considered as the system response to investigate the variation resulting from each combination and subsequently to explore the significance of each input parameter in the simulations
The higher coefficient of variation values for the flooded area indicates that it is much more sensitive than the local water level. This result is important because in most of the applications, the hydrodynamic models are calibrated based on local variables with some known inputs and some particular combinations of calibrated inputs, which after all can correspond to a quite different flooded area if a different combination of calibrated inputs was used
Summary
The use of 2D hydrodynamic models is common in applications like floods or water quality assessment (e.g., Yu & Lane 2006; Park et al 2014; Zischg et al 2018) Those models, based on the numerical solution of the 2D shallow water equations (SWEs), use different types of input parameters with complex domain spaces (e.g., hydrological data, floodplain and channel geometry, initial and boundary conditions, and roughness). Most of these parameters cannot be measured directly and can only be inferred by calibration to observed system responses (Ghasemizade et al 2017; Zadeh et al 2017). In 2D simulations, the analysis has been extended to other inputs such as topography/bathymetry and digital terrain model (DTM) resolution (e.g., Mejia & Reed 2011; Neal et al 2015; van Vuren et al 2015; Abily et al 2016; Savage et al 2016; Lim & Brandt 2019), mesh type, and mesh resolution
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