On the use of 1D and coupled 1D-2D modelling approaches for assessment of flood damage in urban areas

TLDR

Urban flooding is a growing global problem that demands cost‑effective management, prompting the development of diverse modelling approaches ranging from standard one‑dimensional (1D) channel models to newer coupled 1D‑2D representations whose predictive performance can differ. The paper investigates how 1D and coupled 1D‑2D modelling approaches differ in predictive capability for urban flood analysis over irregular terrain. The authors compare 1D and 1D‑2D models by applying them to a St Maarten case study, evaluating how terrain representation and mapping techniques affect predictions and offering guidance on tool selection and key considerations for reliable urban flood analyses. They find that 1D models accurately predict channel flow in suitable terrains, but 2D projections are constrained by terrain representation and mapping methods, highlighting the need for careful tool choice in urban flood assessments. Keywords: urban flood modelling, 1D modelling, 1D‑2D modelling.

Abstract

Abstract Urban flooding has become an increasingly important problem and a growing social issue around the world. Since it continues to be regarded as an almost inevitable danger, the development of cost-effective flood management strategies has become of the utmost importance for many cities, and particularly for those cities in developing countries where the financial resources for recovery from flood-related disasters are almost nonexistent. As a consequence, there is nowadays a range of modelling approaches available for modelling floods and developing flood management strategies. Typically, one-dimensional (1D) hydrodynamic models are used as a standard industry practice. More recently, however, model formulations have included a 1D representation of the main channels and a 2D representation of the floodplains. Since the physical process of describing exchanges of flows with the floodplains can be represented in different ways, the predictive capability of the different modelling approaches can also vary. The present paper explores the difference in predictive capabilities of 1D and 1D-2D modelling approaches for the purpose of urban flood analysis across irregular terrains. It is shown, as expected, that in the case of terrains suited to exclusively 1D models the prediction of flow variables along the channel can be realistic, but that, when it comes to the projection onto a 2D map, the representation of the terrain topography together with the mapping techniques that are employed introduce a limiting factor in their successful application. Practical implications of these two modelling approaches are analysed and illustrated on a case study from St Maarten, NA. The results of this study provide users of numerical models with information that can be used to aid them in determining which tool to use and which aspects to consider in order to make more reliable analyses of flooding processes in urban areas. Keywords: urban flood modelling1D modelling1D-2D modelling