Hydrodynamics of long-duration urban floods: experiments and numerical modelling

Abstract

Abstract. Flood risk in urbanized areas raises increasing concerns as a result of demographic and climate changes. Hydraulic modelling is a key component of urban flood risk analysis. Yet, detailed validation data are still lacking for comprehensively validating hydraulic modelling of inundation flow in urbanized floodplains. In this study, we present an experimental model of inundation flow in a typical European urban district and we compare the experimental observations with predictions by a shallow-water numerical model. The setup is 5 m × 5 m and involves seven streets along each direction, leading to 49 intersections. Different inflow discharges and flow partitions were tested. The performance of the numerical model is assessed and the upscaling of the experimental observations to the field is discussed.

Variance based sensitivity analysis of 1D and 2D hydraulic models: An experimental urban flood case

“…Moreover it quantifies the filtering effect of the topography on the discharge distribution through the whole district as suggested by [14] which is confirmed by the downstream discharge sensitivity to upstream inflow that is barely null. The sensitivity of downstream discharge repartition to a uniform roughness is shown to be relatively low on the tested configurations as suggested by [4] with forward SW model runs on a Cartesian grid. Concerning the street outlet discharge, different sensitivity patterns are obtained with a variance explained at 100% by the downstream water height, or almost equally explained by the downstream water height and the upstream faces discharge; the friction coefficient being only involved in some particular streets.…”

“…2D SW models are able to model recirculation zones and mixing layers (recall with depth averaged velocities) and then the corresponding localized head losses, hence it is not necessary to account for those effects with the friction coefficient. The uniform roughness calibrated in this study for the 2D SW model (including a k − ε turbulence model as suggested by [4] for better simulating recirculation zones) is K 2D = 100m 1/3 .s −1 . This latest value is a good M A N U S C R I P T proof of 2D SW ability in reproducing such flows since it is very close to the "real experimental" one -recall 80 − 100m 1/3 .s −1 is expected for plexiglass.…”

“…Flood inundation maps are commonly generated with a 2D Saint-Venant shallow water (SW) model consisting in depth averaged Navier-Stokes equations (e.g. [4,24,30]) where uncertainty sources can stem from the model structure or the parameterization (e.g. basal friction), or the initial and boundary conditions (bathymetry and source terms).…”

Mapping of uplift hazard due to rising groundwater level during floods

“…Hydraulic models linked to computer‐aided design (CAD) or geographic information systems (GIS) systems provide spatial data for the evaluation and quantification of groundwater‐related hazard and its representation using computer mapping techniques (Büchele et al, 2006; Hughes et al, 2001; MacDonald, Bloomfield, et al, 2008; Morris, Cobby, Zaidman, & Fisher, 2015; Naughton, Johnston, McCormack, & Gill, 2015; Sommer, 2007). Such techniques are routinely applied in the development of flood risk management plans which take into account surface flooding (Arrault et al, 2016; CDS, 2013; Directive, 2007). However, there is a lack of studies focused on the mapping of the hazard induced by groundwater, namely due to the uplift on the topsoil layers during flood events.…”

Formation, breaching and flood consequences of a landslide dam near Bujumbura, Burundi

“…This model has been extensively validated and applied for simulating flow induced by dam and dike breaching (Dewals et al, 2011;Roger et al, 2009) as well as for conducting flood risk analysis (Arrault et al, 2016;Beckers et al, 2013;Bruwier et al, 2015;Detrembleur et al, 2015;Ernst et al, 2010). We detail below how friction was parametrized in the hydraulic model, as well as the prescribed boundary conditions and the modelling 155 procedure.…”