London has been identified by the Greater London Authority (GLA) as being at high risk of flash flooding. The authority proposed a concept of turning London into a “sponge city,” which would involve urban areas designed to absorb and hold rainwater to mitigate flood impacts. The blueprint is still in the conceptual phase, though flash floods that hit the city last July led to the formation of the Surface Water Strategic Group. The group was created to develop a flood strategy for major cities and is expected to announce a London-wide flooding plan later this year.
When there is heavy rainfall, excess water enters sewerage systems and overwhelms it, leading to surface flooding. According to a report released in 2022 by the London Climate Resilience Review, London is underprepared for climate change. The report identified surface flooding as one of the most lethal issues affecting all and called for the development of a plan to curb the impacts of flooding.
China was among the first to introduce the sponge city concept after the lower Yangtze River Delta region suffered severe flash floods in 2013. The policy have a multibillion-dollar funding, and the plan seeks to prevent the need to remove water through the use of large-scale infrastructure, such as sewage pipes. Green and blue spaces are utilized to capture rainwater.
Although London has an array of green spaces, computer modelling found London to be the second-least spongy city among the seven compared cities, with a rating of 22%. The rating indicates that London has a low ability to absorb rainwater, proving that the implementation of the sponge city concept is challenging. The concept relies heavily on the use of sustainable drainage systems (SuDS), which are projects designed to manage excess rainwater on a local scale. Examples of these are green roofs, permeable pavements, rain gardens, detention basins, and swales.
The SuDS and sponge city concept present a viable solution to surface flooding attributed to heavy rainfall. Creating a sponge city in a city like London, however, comes with challenges such as high costs and lack of space. The Greater London Authority predicts that if climate change continues, flash flooding in the city is likely to increase. It’s no longer a question of if it floods but when
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