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Global flood management is a major issue for most cities which have to deal with worsening factors such as climate change and fast urban growth. Computer models have been used to model and understand urban flooding on a local scale in cities (25–50 km2). It has been practically impossible to model bigger cities in one go in sufficiently high resolution due to the heavy computations involved. The present paper describes a new modelling approach for urban flooding which allows modelling on large city scale (1000 km2) while keeping sufficient resolution, e.g. 5 m or 10 m grid. The multicell approach is applied for the city of Beijing for July 21st, 2012 flood event. Model results are compared to testimonials from the 2012 event. Comparison to traditional 2D urban flood computations shows that the multicell approach is much faster than standard detailed models while keeping a suitable level of precision. [ABSTRACT FROM AUTHOR]

Recently, local floods have become severely threatening to urban safety in China. As the capital city, Beijing has experienced serious local floods every year. In this paper spatial characteristics of local floods in the Beijing urban area were studied. Local flood locations changed and appeared as a spatial expansion trend from 1981 to 2011. Since all of the local floods were located in built-up areas, we further studied the relation between local floods and built-up areas using the spatial statistics of Geographic Information Systems. The results show that they had the same directional development trend which indicated local floods would get worse with the expansion of built-up areas. It also found that most local floods were located where there were high densities of drainage pipes, so we could infer that pipe systems should not be the only way to solve local floods due to their failures and negative effects. [ABSTRACT FROM AUTHOR]

Large-scale centralised wastewater treatment system has often prevailed in industrial countries, and has been regarded as a successful approach during the last century. However, transfer of this highly water-consuming system and so-called 'end-of-pipe' technology to developing countries, especially in fast-growing cities with scarce water resources, has been extremely limited. Decentralized water treatment is not a new technology and has been successfully implemented in many rural areas worldwide. However, there are few applications in urban areas. This study at Tianxiu Garden in Beijing, China, investigated the potential and feasibility of water management based on a decentralized approach, but modified for application of greywater recycling and rainwater harvesting in a densely populated semi-urban area. A high degree of drinking water substitution (more than 25%) could not be attained by rainwater harvesting. Recycling of treated greywater for toilet flushing was shown to be an efficient method for minimisation of drinking water consumption, and a more suitable technique than rainwater harvesting for saving water in Beijing, China. [ABSTRACT FROM AUTHOR]