Effects of low impact development on the stormwater runoff and pollution control

Highlights

• The value of LID practice was confirmed by sensitivity analysis.

• The suitable combination scheme was proposed based on single measure analysis.

• The pollutant reduction effect of different installation locations LID measures was analyzed.

• Horizontal connection scheme was also proposed and achieved a better result.

Abstract

The frequent urbanization and extreme rainfall events have posed the threat to the urban environment. The implementation of low impact development (LID) practices with great potential for control urban flood and overflow pollution is not comprehensively understood yet due to the influence of complex factors (i.e., hydrological pattern, installation location, and vertical parameter setting). In this study, the hydraulic and water quality model were used to analyze the hydrological and pollution reduction of outfall and storage under different hydrological patterns, vertical parameter setting, and green infrastructure installation locations, which can determine the best implementation of the scheme for overflow pollution control. The results showed that nine parameters of the vertical layer regarding the four parameters impacted the peak value and load of suspended solids (SS). The combination scheme of the LID practices was further proposed based on the selection and analysis of the single LID practice. Besides, considering the installation location, the downstream installed location was a better choice. The horizontal connection of overflow runoff and pollution could be reduced by up to 9.75% and 36.46%, respectively. In addition, the horizontal connection can effectively reduce the peak value of inflow and pollutants at the time of assessing storage tank impact, which reach the maximum of 14.08% and 29.25%, respectively. The pollutants distribution became uniform and showed better resilience against rainfall intensity, which is beneficial to the management of stormwater. Our findings can provide guidance for Sponge City construction and effectively alleviate the combined sewer overflow.

Introduction

In recent years, the increase of impervious surfaces in cities due to accelerated urbanization and the frequent occurrence of extreme rainfall events caused by climate change had eventually led to urban diseases such as waterlogging and flooding in cities (Leng et al., 2020; Wang et al., 2020). Flooding and waterlogging not only cause significant property damage and loss of human life but also cause the pollution of water bodies and impacts on the ecosystem (Baek et al., 2020; Bixler et al., 2020). Therefore, the exploration of stormwater management measures, especially flood reduction and environment protection measures, is an urgent issue, leading to widespread concern from scholars and engineers.

Traditional stormwater management relying on drainage system retrofitting is not adaptive to climate change and accelerated urbanization (Kourtis et al., 2020) and is also insufficient for managing stormwater pollution (Jiang et al., 2018). Recently, the construction of Sponge City in China, also known as Sustainable Urban Drainage System (SUDS) in England, Water Sensitive Urban Design (WSUD) in Australia, and LID in North America, has brought light to widely used urban stormwater management and proven effective in practical stormwater management (Nguyen et al., 2020). The purpose of LID implementation is to restore the city to its natural state, and the main element is to restore the natural circulation of runoff (Eckart et al., 2017). It can enhance stormwater runoff reduction, peak flow reduction, peak time lag, and pollutant reduction by increasing retain, infiltration, and so on (Ma et al., 2019; Qin et al., 2013; Taghizadeh et al., 2021; Wang et al., 2021).

The drainage modeling, such as Stormwater management model (SWMM), MIKE Urban, InfoWorks ICM, and other hydrological models, has been widely reported to be applied to stormwater management and achieved satisfied results (Baek et al., 2015; Song et al., 2020; Tan et al., 2019). As an inspiring strategy for urban flood control, numerous studies have focused on LID practices including flood reduction analysis, location selection, combined LID scheme determination, and so on (dos Santos et al., 2021; Liao et al., 2015; Samouei and Özger, 2020; Yao et al., 2020). However, the capacity of Sponge City is not only applied for the runoff control but also for the pollutant reduction (Zheng et al., 2021). Recently, the issues on stormwater pollution from have aroused the attention of the public (Zhang et al., 2021b). Compared to the runoff control, the migration process of the stormwater pollutants including the build-up, wash-off, and discharge approaches is complex (Bonhomme and Petrucci, 2017). In terms of the build-up process, the accumulation of the pollutant of the study area is described during the dry weather, which can be influenced by antecedent dry-weather periods (ADWP) and land use (Yang et al., 2021b). The wash-off process can describe the flushing of pollutants by the surface runoff during the wet weather, which can be affected by the rainfall pattern and the build-up approach (Zhao and Li, 2013). The discharge approach reflects the transport of pollutants through the drainage system. The drainage modeling can provide the full understanding of the pollutant migration process and optimize the strategy on the stormwater pollution on a city scale by using both hydraulic and water quality models (Xiong et al., 2021). In this regard, consequently, the drainage modeling can be selected as a tool for this study.

Most studies have focused on the single influencing factor (e.g., rainfall pattern) for the LID implementation assessment, which is insufficient for stormwater runoff and pollution control. Except for the rainfall pattern, the performance of the LID practices can also be influenced by their implementation strategy and characteristics. Hence, it is necessary to assess the complex interactive effect among different influencing factors on the performance of the LID practices (Yang et al., 2021b).

Therefore, in this study, an integrated hydraulic and water quality model was employed to assess (1) the runoff and pollutant variation before and after the implementation of the LID practices, and (2) the different influencing factors (i.e., rainfall intensity, ADWP, different location, different combination methods, and the characteristics of LID practices) on the hydrological and pollution reduction performance of the LID practices. The results of this study would promote the new urban stormwater management by completely analyzing the LID practices.