Meta-Analysis of Storm Water Impacts in Urbanized Cities Including Runoff Control and Mitigation Strategies

The rate of urbanization has been impacted by global economic growth. A strong economy results in more people moving to already crowded urban centers to take advantage of increased employment opportunities often resulting in sprawling of the urban area. More natural land resources are being exploited to accommodate these anthropogenic activities. Subsequently, numerous natural land resources such as green areas or porous soil, which are less flood-prone and more permeable are being converted into buildings, parking lots, roads and underground utilities that are less permeable to storm water runoff from rain events. With the diminishing of the natural landscape that can drain storm water during a rainfall event, urban underground drainage systems are being designed and built to tackle the excess runoff resulting from urbanization. However, the rapid pace of urbanization has profoundly affected the formation of urban runoff thus resulting in the existing underground drainage system being unable to handle current flow conditions. This paper discusses storm water impacts in urbanized areas globally by reviewing historical storm water events and mitigation strategies accompanied with runoff reduction performance that are considered simultaneously for the purpose of relieving the stress on underground drainage systems. It was found that the stormwater impact on ten selected typical urban areas were enormously destructive followed by billions of direct economy loss, fatalities, damaged properties and residents’ relocations. Furthermore, the meta-analysis of selected six runoff mitigation methods indicated that the average runoff reduction percent ranged from 43% to 61% under different rain events in various installed sites across different event years.