Porosity Models for Large-Scale Urban Flood Modelling: A Review

Abstract

In the context of large-scale urban flood modeling, porosity shallow-water models enable a considerable speed-up in computations while preserving information on subgrid topography. Over the last two decades, major improvements have been brought to these models, but a single generally accepted model formulation has not yet been reached. Instead, existing models vary in many respects. Some studies define porosity parameters at the scale of the computational cells or cell interfaces, while others treat the urban area as a continuum and introduce statistically defined porosity parameters. The porosity parameters are considered either isotropic or anisotropic and depth-independent or depth-dependent. The underlying flow models are based either on the full shallow-water equations or approximations thereof, with various flow resistance parameterizations. Here, we provide a review of the spectrum of porosity models developed so far for large-scale urban flood modeling.

How Urban Form Impacts Flooding

“…However, in pursuit of computational efficacy, we rely on a shallow-water hydrodynamic model [22] and produce thousands of fine-resolution, building-resolved simulations for different realizations of urban form. Shallow-water theory builds on the assumption of hydrostatic pressure and nearly-horizontal flow, and shallow-water models have been validated at neighborhood and larger scales by extensive laboratory and field studies and urban flood modeling [19,[23][24][25][26][27][28]. While urban flooding can involve high levels of complexity such as flows into basements, subway systems, and usually involves a mix of underground flows through storm pipes and overland flow along streets [29], we are specifically interested here in the depth and velocity of overland flow through cities caused by the amount of overland flow in response to hazard drivers (e.g., rainfall, overbank flows, storm water surcharge).…”

Shape optimization for the mitigation of coastal erosion via porous shallow water equations

“…To model a permeable obstacle, which can be exemplifying interpreted as a geotextile tube, a porosity parameter is introduced. Porous SWE models are being paid increasing attention throughout the last decade, mostly because its ability to perform large‐scale urban flood modeling 13 . Over the years a variety of models have been introduced differing in terms of conceptual, mathematical, and numerical aspects 14‐16 .…”

“…Porous SWE models are being paid increasing attention throughout the last decade, mostly because its ability to perform large-scale urban flood modeling. 13 Over the years a variety of models have been introduced differing in terms of conceptual, mathematical, and numerical aspects. [14][15][16] Our model mainly builds up on Reference 14, such that we are dealing with a single, depth-independent porosity parameter in the definition of the SWE.…”

Shape Optimization for the Mitigation of Coastal Erosion via Porous Shallow Water Equations

“…To model a permeable obstacle, which can be exemplifying interpreted as a bag filled with sand, a porosity parameter is introduced. Porous SWE models are being paid increasing attention throughout the last decade, mostly because its ability to perform large-scale urban flood modelling [12]. Over the years a variety of models have been introduced differing in terms of conceptual, mathematical and numerical aspects.…”