Numerical Modeling the Flood and Pollutant Transport Processes in Residential Areas with Different Land Use Types

Abstract

Large-scale flooding causes widespread disaster, and harmful pollutant concentration in water following flood affects public safety and the environment. In this study, a numerical model for solving the 2D shallow water equations and the solute transport equation is proposed to simulate overland flood and pollutant transport caused by floods. The present model is verified by comparing the predictions with the analytical solutions and simulation results; sufficiently high computational accuracy is achieved. The model is also used to simulate flood inundation and pollution spread in the area of Hun and Taizi Lane (HTL) in China due to river dike breaches; the results show that the coupling model has excellent performance for simulating the flooding process and the temporal and spatial distribution of pollutants in urban or rural areas. We use remote sensing techniques to acquire the land coverage in the area of HTL based on Landsat TM satellites. The impacts of changed land use on mitigation of flooding waves and pollutant spread are investigated; the results indicate that the land cover changes have an obvious influence on the evolution process of flood waves and pollutant transport in the study areas, where the transport of pollutants is very dynamic during flood inundation in HTL area. Furthermore, the motion of pollutants considering anisotropic diffusion is more reasonable than that due to isotropic dispersion in simulating pollutant transport associated with the flood in urban or farmland environments.

Formulations and Diffusivity Coefficients of the 2D Depth‐Averaged Advection‐Diffusion Models: A Literature Review

“…In a limited number of studies (Duan, 2004;Fang et al, 2022;Wan et al, 2020), the dispersive fluxes are expressed as a function of the gradient of the product of the water depth and scalar concentration hC instead of the gradient of concentration C alone. Accordingly, the RHS of Equation 3 is formulated as follows:…”

“…Approach ① was used solely in studies which either (a) neglect the dispersion-diffusion effects (i.e., coefficient D set to zero for model application, such as Murillo et al, 2006or Behzadi et al, 2018, (b) do not report which value is assigned to the coefficient (Gualtieri, 2010;Li & Duffy, 2012), or (c) use arbitrarily set values for the diffusivity (Pathirana et al, 2011). Approach ② was used by Fang et al (2022) in combination with a conventional (direction-independent) evaluation of the shear velocity, resulting in an isotropic diffusivity tensor. In contrast, Morales-Hernandez et al ( 2019) also considered a single coefficient, in line with approach ②, but they used direction-dependent values for the shear velocity so that the resulting diffusivity tensor was nonisotropic.…”

“…In a limited number of studies (Duan, 2004; Fang et al., 2022; Wan et al., 2020), the dispersive fluxes are expressed as a function of the gradient of the product of the water depth and scalar concentration hC instead of the gradient of concentration C alone. Accordingly, the RHS of Equation is formulated as follows: $$$\text{RHS}=\frac{\partial }{\partial x}\left[{D}_{x}\frac{\partial }{\partial x}(hC)+{D}_{xy}\frac{\partial }{\partial y}(hC)\right]+\frac{\partial }{\partial y}\left[{D}_{yx}\frac{\partial }{\partial x}(hC)+{D}_{y}\frac{\partial }{\partial y}(hC)\right]+S$$$ …”

“…In contrast, Fang et al. (2022) used a conventional evaluation of the friction velocity u * , so in this case u * L = u * T = u * .…”

“…Similarly, accurately predicting the mixing of accidently released pollutants in rivers and coastal areas is instrumental to inform pollution control strategies and environmental protection (Li & Duffy, 2012; Park et al., 2020). Flood events affecting urbanized floodplains may damage wastewater treatment plants or other facilities that have the potential to release pollutants in the environment (Fang et al., 2022; Murillo et al., 2006). Release of pollutant during urban floods may also result from surcharging sewer systems (Sämann et al., 2019).…”