Influence of sewer network models on urban flood damage assessment based on coupled 1D/2D models

Abstract

One of the main steps in assessing flood risk in urbanised areas is the quantification of damage costs. Damage is often estimated based on depth-damage curves for which depth maps are obtained (ideally) from coupled flood models. While the comparative analysis of flood damage models has been extensively researched in the literature, the influence of the underlying sewer network model has not been investigated. In this study, a 2D locally inertial equations flood risk analysis model (GWM) is coupled with two stormwater models (SWMM, tested with three different configurations, and SIPSON). The assessment of the network performance is made through the total exchanged volume between the surface and stormwater system, the surcharged conduits and manholes, maximum overland inundation and costs using a stepped version of the multi-coloured manual depth-damage curves for continuous urban fabric. The models behave similarly; however, they do show differences in the head pressures, number of surcharged manholes and maximum depth in some locations. The case study results show that despite the good agreement in damage between the four configurations (≈6% maximum disagreement), some localised high differences in maximum depth observed [0.25 (m)] exist. It was also shown that SWMM needs to be calibrated in order to perform similarly to Preissmann slot models.

A comparison of three dual drainage models: shallow water vs local inertial vs diffusive wave

“…One of the first proposals for dual drainage was made by Ellis et al (1982) using SWMM to design Dual Drainage 1D/1D Systems, where the two systems remained separated although they were calibrated as if they worked together. More recently the approach has seen some significant improvements by Prodanovic et al, (1998);D et al, (1999); Hsu et al, (2002); Nasello and Tucciarelli, (2005); Chen et al, (2007); Leandro et al, (2009) ;Mahdizadeh et al, (2011Mahdizadeh et al, ( , 2012; Seyoum et al, (2012); Borsche and Klar, (2014); Fraga et al,(2015); Chen et al,(2015); Russo et al,(2015); Martins et al,(2016c); Leandro et al, (2016). et al, (1999) proposed an approach to the dual drainage concept to better replicate the urban flood conditions with an integrated sewer and surface hydraulic model.…”

Validation of 2D shock capturing flood models around a surcharging manhole

“…Nonetheless, 3D modelling of these events system yields prohibitive runtime costs and is currently unforeseeable at street scale in the urban environment (Cea et al 2010). Practically, it has become common to tackle modelling of sewer-to-floodplain flow interaction as a compound system consisting of 2D surface and 1D sewer-flow systems (Chen et al 2015, Lee et al 2013, Martins et al 2016, Seyoum et al 2012.…”

“…Fully-coupled approaches involve implicit coupling, of a 1D or 2D surface flow model, with a 1D unsteady pipe flow solver (Chen et al 2015, Djordjević et al 2005, Lee et al 2013, Martins et al 2016, Seyoum et al 2012. In many of these works, sewer overflow is accounted for using only one computational cell, and for real-site applications (Martins et al 2016 conditions to produce systematic increase in the sewer surcharge rate into a shallow flow over a floodplain.…”

“…In many of these works, sewer overflow is accounted for using only one computational cell, and for real-site applications (Martins et al 2016 conditions to produce systematic increase in the sewer surcharge rate into a shallow flow over a floodplain. Two well-established FV numerical solvers to the 2D SWE are selected based on two approximate Riemann solvers, HLLC and Roe, and on different (non-uniform) mesh-types, i.e.…”

Wetting and drying numerical treatments for the Roe Riemann scheme

“…FR1 is based on the numerical treatment presented by Leandro et al (2014), extended to GWM in Martins, Leandro, and Djordjević (2016) and herein for SWE. It implies a redefinition of the flux and can be considered a flux restricting, depth extrapolation numerical treatment or predictor-corrector.…”