Flood inundation mapping in small and ungauged basins: sensitivity analysis using the EBA4SUB and HEC-RAS modeling approach

Andrea Petroselli,Jana Vojteková,Matej Vojtek,Shahla Asgharinia

doi:10.2166/nh.2019.163

Abstract

Abstract Flood mapping is an important part of flood risk analysis and management as its result is the visualization of flood hazard in terms of flood depth and extent. However, flood mapping strongly depends on the selected modeling approach. Furthermore, model input data usually incorporate uncertainties that may vary significantly in time and space. In this study, the EBA4SUB (Event-Based Approach for Small and Ungauged Basins) hydrologic model and the one-dimensional HEC-RAS (Hydrologic Engineering Center's River Analysis System) hydraulic model were selected for evaluating their sensitivity, in terms of simulated flood area (FA) and volume (FV), to different combinations of input parameters. Results of hydrologic modeling highlight the great variation of design peak discharges which strongly influence the modeled FA and FV. The sensitivity of FA and FV to excess rainfall determination was several times larger than the sensitivity to the routing propagation for two assumed gross rainfall distributions (rectangular and Chicago), which highlights the importance of the correct estimation of soil and land use properties affecting the infiltration estimation. Moreover, the sensitivity of FA and FV to the roughness parameter was 1.5–2 times greater than the sensitivity to the cross-section parameter, yet, stressing the importance of input parameters for hydraulic modeling.

Highlights

Flood mapping is a crucial element of flood risk management since it provides the delineation of flood depth and extent in flood-prone areas
The creation of flood maps is usually performed using a combination of hydrologic and hydraulic models that is challenging in case of small and ungauged basins where the calibration of advanced hydrologic models is difficult due to lack of observed discharge data (Grimaldi et al a; Szymczak & Krezałek )
Each combination of Tc, curve number (CN) and gross rainfall distribution (GRD) furnishes a design hydrograph characterized by a peak discharge

Summary

Introduction

Flood mapping is a crucial element of flood risk management since it provides the delineation of flood depth and extent in flood-prone areas. The creation of flood maps is usually performed using a combination of hydrologic and hydraulic models that is challenging in case of small and ungauged basins where the calibration of advanced hydrologic models is difficult due to lack of observed discharge data (Grimaldi et al a; Szymczak & Krez ̇ ałek ). In order to estimate the design peak discharge or the design hydrograph for ungauged basins, different hydrologic models are usually applied (Petroselli et al ). The limitation of 1D hydraulic models is that they are not able to provide information on the character and direction of flow as well as the way of flowing off the obstacles

Objectives

Results

Conclusion