Urban flooding has become a serious issue in most Chinese cities due to rapid urbanization and extreme weather, as evidenced by severe events in Beijing (2012), Ningbo (2013), Guangzhou (2015), Wuhan (2016), Shenzhen (2019), and Chongqing (2020). The Chinese “Sponge City Program” (SCP), initiated in 2013 and adopted by 30 pilot cities, is developing solutions to manage urban flood risk, purify stormwater, and provide water storage opportunities for future usage. Emerging challenges to the continued implementation of Sponge Cities include (1) uncertainty regarding future hydrological conditions related to climate change projections, which complicates urban planning and designing infrastructure that will be fit for purpose over its intended operating life, and (2) the competing priorities of stakeholders and their reluctance to make trade-offs, which obstruct future investment in the SCP. Nature-Based Solutions (NBS) is an umbrella concept that emerged from Europe, which encourages the holistic idea of considering wider options that combine “Blue–Green” practices with traditional engineering to deliver “integrated systems of Blue–Green–Grey infrastructure”. NBS includes interventions making use of natural processes and ecosystem services for functional purposes, and this could help to improve current pilot SCP practices. This manuscript reviews the development of the SCP, focusing on its construction and design aspects, and discusses how approaches using NBS could be included in the SCP to tackle not only urban water challenges but also a wide range of social and environmental challenges, including human health, pollution (via nutrients, metals, sediments, plastics, etc.), flood risk, and biodiversity.

Fine particulate matter in the lower atmosphere (PM_2.5) continues to be a major public health problem globally. Identifying the key contributors to PM_2.5 pollution is important in monitoring and managing atmospheric quality, for example, in controlling haze. Previous research has been aimed at quantifying the relationship between PM_2.5 values and their underlying factors, but the spatial and temporal dynamics of these factors are not well understood. Based on random forest and Shapley additive explanation (SHAP) algorithms, this study analyses the spatiotemporal variations in selected key factors influencing PM_2.5 in Zhejiang Province, China, for the period 2000–2019. The results indicate that, while factors influencing PM_2.5 varied significantly during the period studied, SHAP values suggest that there is consistency in their relative importance as follows: meteorological factors (e.g., atmospheric pressure) > socioeconomic factors (e.g., gross domestic product, GDP) > topography and land cover factors (e.g., elevation). The contribution of GDP and transportation factors initially increased but has declined in the recent past, indicating that economic and infrastructural development does not necessarily result in increased PM_2.5 concentrations. Vegetation productivity, as indicated by changes in NDVI, is demonstrated to have become more important in improving air quality, and the area of the province over which it constrains PM_2.5 concentrations has increased between 2000 and 2019. Mapping of SHAP values suggests that, although the relative importance of industrial emissions has declined during the period studied, the actual area positively impacted by such emissions has actually increased. Despite developments in government policy, greater efforts to conserve energy and reduce emissions are still needed. The study further demonstrates that the combination of random forest and SHAP methods provides a valuable means to identify regional differences in key factors affecting atmospheric PM_2.5 values and offers a reliable reference for pollution control strategies.

Rapid urbanization has sharply increased the pressure of urban water issues (e.g., urban flooding and water pollution) in the Chinese megacities during last three decades. Sustainable urban water management approaches, such as Nature Based Solutions (NBS) and Low Impact Developments (LIDs), have successfully delivered long-term benefits to cities in Europe and North America. Similarly, the Chinese Sponge City Program (SCP) initiated in 2013 and experimented in 30 pilot Chinese cities. This paper reviewed the first stage of the SCP from 2015 to 2020 by using observation, Semi-Structured Interview (SSI) and Focus Group Approach (FGA) in context of Gui'an New Distinct, SW China to investigate the SCP progress and issues: (1). whether it is effectively solving urban water issues; (2). if there are any major challenges and barriers in the SCP practice. The findings of this case study provide potential solutions for improving the SCP and sustainable urban water management and possibly transform to other Sponge Cities in China.