Flood hazard assessment: comparison of 1D and 2D hydraulic models

Abstract

The 'Floods Directive' 2007/60/CE by the European Parliament requires the characterization of flood hazard by multi-scenario hydraulic analyses, based on the estimation of flow velocity and water depth or free-surface level over flooded areas. In principle, this evaluation demands a complete analysis of the watershed hydraulics, based on two-or even three-dimensional modelling. Since the latter, however, may hardly be applied at the watershed scale, 1D and 2D analyses represent the usual approaches to hydraulic risk mapping. The present work discusses a comprehensive comparison between 1D and 2D modelling of floods in meandering channels, aimed to guide practitioners in the confident choice of a tradeoff between complexity and accuracy. In particular, both numerical models were applied to a typical river morphology, represented by few shape parameters. Steady-flow conditions have been generally assumed; furthermore selected numerical experiments have been run under unsteady flow to investigate the effect of the time-varying hydrographs. Uniform-flow framework is considered for the 1D analysis, whereas 2D modelling is performed using the CCHE2D code developed at the National Center for Computational Hydroscience and Engineering, University of Mississippi. The models' results are compared in terms of computed stage -discharge hydrograph, shear stress distribution and free-surface elevation.

Validation of 2D flood models with insurance claims

“…Another increasing use of flood inundation models is the coupling of flood models with hydrologic and hydrometeorologic models within a model cascade or a coupled component modelling framework at the river basin scale (e.g., Biancamaria et al 2009, Falter et al 2015, Zhu et al 2016, Felder et al 2017. Thus, a variety of inundation models exist for different purposes (e.g., Horritt and Bates 2001a, Hunter et al 2007, Chatterjee et al 2008, Crispino et al 2015, Courty et al 2017. Developers are validating the models with a broad set of validation techniques and data.…”

“…For evaluating newly developed models, a benchmark test against established models or models that represent an industry standard is sometimes done (Neal et al 2012a). The comparison of the flooded areas computed by different models is shown in several studies (Horritt and Bates 2001a, Horritt and Bates 2002, Tayefi et al 2007, Chatterjee et al 2008, Fewtrell et al 2008, Castellarin et al 2009, Neal et al 2012a, Neal et al 2012b, Crispino et al 2015, Trigg et al 2016, Vozinaki et al 2016, Lavoie et al 2017. However, the main limiting factor for validating inundation models is often the lack of validation data (Neal et al 2012a).…”

Flood Mapping Proposal in Small Watersheds: A Case Study of the Rebollos and Miranda Ephemeral Streams (Cartagena, Spain)

“…The expansion of artificial surfaces, the modification of the land with constructions crossing the valley to mitigate the lack of connectivity, the use of plastics for irrigated crops, and the invasion of the river mobility spaces are phenomena that simulations sometimes fail to recreate. This is because of the complexity of the physical processes of reality that must be simulated for the hydraulic method [58,59]. The areas flooded on 13 September 2019 reveal that flood hazard mapping has not been carried out for the whole watershed.…”

Citlivostní analýza vybraných vstupních parametrů numerického modelu HEC-RAS při hydraulických výpočtech proudění vody v korytech toků a záplavových územích

“…Obecně je problematice srovnání 1D, 2D a 1D/2D hydrodynamických modelů věnována řada publikací, viz např. [10][11][12][13][14][15][16][17].…”