Department of Urban Engineering, The University of Tokyo, Tokyo, Japan.
Water Sci Technol. 2013;68(3):544-51. doi: 10.2166/wst.2013.253.
Combined sewer overflow (CSO) from urban areas is recognized as a major pollutant source to the receiving waters during wet weather. This study attempts to categorize rainfall events and corresponding CSO behaviours to reveal the relationship between rainfall patterns and CSO behaviours in the Shingashi urban drainage areas of Tokyo, Japan where complete service by a combined sewer system (CSS) and CSO often takes place. In addition, outfalls based on their annual overflow behaviours were characterized for effective storm water management. All 117 rainfall events recorded in 2007 were simulated by a distributed model InfoWorks CS to obtain CSO behaviours. The rainfall events were classified based on two sets of parameters of rainfall pattern as well as CSO behaviours. Clustered rainfall and CSO groups were linked by similarity analysis. Results showed that both small and extreme rainfalls had strong correlations with the CSO behaviours, while moderate rainfall had a weak relationship. This indicates that important and negligible rainfalls from the viewpoint of CSO could be identified by rainfall patterns, while influences from the drainage area and network should be taken into account when estimating moderate rainfall-induced CSO. Additionally, outfalls were finally categorized into six groups indicating different levels of impact on the environment.
城市合流制污水溢流（CSO）是在雨季受纳水体的主要污染物来源之一。本研究旨在对降雨事件和相应的 CSO 行为进行分类，以揭示日本东京新御徒町城市排水区的降雨模式与 CSO 行为之间的关系，在该地区，完整的合流制排水系统（CSS）和 CSO 经常同时运行。此外，还根据其年度溢流行为对排放口进行了特征描述，以便进行有效的雨水管理。利用分布式模型 InfoWorks CS 对 2007 年记录的 117 次降雨事件进行了模拟，以获得 CSO 行为。根据降雨模式和 CSO 行为的两组参数对降雨事件进行了分类。通过相似性分析将聚类的降雨和 CSO 组联系起来。结果表明，小到极端降雨与 CSO 行为有很强的相关性，而中雨则相关性较弱。这表明，从 CSO 的角度来看，可以通过降雨模式识别重要和可忽略的降雨，而在估计由中雨引起的 CSO 时，应考虑排水区和管网的影响。此外，最终将排放口分为六组，表明其对环境的影响程度不同。
