Flood impact assessment in urban context. How important is it to couple hydraulic and economic models at a fine scale?

David Nortes Martínez (), Frédéric Grelot (), Cécile Choley and Pascal Finaud-Guyot ()
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David Nortes Martínez: UMR G-EAU - Gestion de l'Eau, Acteurs, Usages - Cirad - Centre de Coopération Internationale en Recherche Agronomique pour le Développement - BRGM - Bureau de Recherches Géologiques et Minières - IRD - Institut de Recherche pour le Développement - AgroParisTech - INRAE - Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement - Institut Agro Montpellier - Institut Agro - Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement
Frédéric Grelot: UMR G-EAU - Gestion de l'Eau, Acteurs, Usages - Cirad - Centre de Coopération Internationale en Recherche Agronomique pour le Développement - BRGM - Bureau de Recherches Géologiques et Minières - IRD - Institut de Recherche pour le Développement - AgroParisTech - INRAE - Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement - Institut Agro Montpellier - Institut Agro - Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement
Cécile Choley: ENGEES - École Nationale du Génie de l'Eau et de l'Environnement de Strasbourg
Pascal Finaud-Guyot: HSM - Hydrosciences Montpellier - IRD - Institut de Recherche pour le Développement - INSU - CNRS - Institut national des sciences de l'Univers - CNRS - Centre National de la Recherche Scientifique - UM - Université de Montpellier, LEMON - Littoral, Environment: MOdels and Numerics - CRISAM - Inria Sophia Antipolis - Méditerranée - Inria - Institut National de Recherche en Informatique et en Automatique - IMAG - Institut Montpelliérain Alexander Grothendieck - CNRS - Centre National de la Recherche Scientifique - UM - Université de Montpellier - HSM - Hydrosciences Montpellier - IRD - Institut de Recherche pour le Développement - INSU - CNRS - Institut national des sciences de l'Univers - CNRS - Centre National de la Recherche Scientifique - UM - Université de Montpellier

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Abstract: Estimating the impacts of flooding in urban areas is of primary importance when qualifying the exposure of territories. One of the difficulties encountered is that the processes at stake involve fine scales (building scale). Classical hydraulic approaches of urban floods consider buildings as obstructions to water flow, without taking into account the flow exchanges between streets and buildings. However, according to the literature, it seems necessary for characterizing material damage and human exposure in terms of buildings' dangerousness. Regarding the estimation of material damage, it is usual to assume that the water levels inside and outside the buildings are the same. This practice does not take into account the hydrostatic effects of flooding. As flood damage functions are very elastic with respect to water levels, especially in the lower values, relatively small differences in water levels can lead to large differences in the assessment of material damage. For these reasons, not taking into account the flow exchanges between streets and buildings may introduce a bias in the estimation of property damage. We propose to analyse how fine-scale approaches (building,) taking into account flows, can influence the characterization of material damage at a larger scale (district). We use the Richelieu district of the city of Nïmes, in the south of France to illustrate our work, taking as reference the 1988 event. We couple hydraulic and economic models to simulate water depths following i) a classical approach of building treatment and ii) an alternative approach explicitly taking into account street-building flow exchanges. The simulated water depths are then fed to the economic model, allowing us to determine, by comparing scenarios, possible bias and its magnitude. The Preliminary results show significant differences in water levels inside buildings compared to outside. In terms of damage, at the district level, not taking into account street-building flows leads to an overestimation of material damage. These results invite us to carry out complementary analyses at higher levels of resolution, by considering the dynamics of the flows inside the buildings and their repercussion in terms of material damage but also of danger.

Date: 2022-05-29
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Published in IAHS-AISH Scientific Assembly 2022, May 2022, Montpellier, France. ⟨10.5194/iahs2022-71⟩

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Persistent link: https://EconPapers.repec.org/RePEc:hal:journl:hal-03814878

DOI: 10.5194/iahs2022-71

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