Cities ‘build green’ to help fight flood risk
By Lauren Hubbard
Last month saw the deadliest freshwater flood-related disaster to hit Japan since 1892. To date, more than 200 people have been confirmed dead with a further 48 reported missing.The floods have highlighted a weakness in the aging city infrastructure, with a heavy impact on production, consumption and tourism.
Numerous other flooding events have occurred in the past year around the world including across South Asia, East Africa and the southern US as a result of hurricanes Harvey and Irma.
These are part of a longer term trend of increasing flood risk. Driven by climate change, the number of flood events has increased by more than 50% this decade. Four times as many flood events are taking place globally compared to 1980.
This increase poses a serious threat to cities, which are home to more than half of the world’s population and multiple high value assets. The new Lloyd’s City Risk Index quantifies the threat flood poses to global economic growth, finding that 279 of the world’s largest cities stand to lose a total of $35bn on average every year.
This threat is likely to increase. It is predicted that by 2050 more than 800 million people will be living in more than 570 coastal cities at risk from just half a metre of sea level rise and just half a metre of flooding caused by weather extremes.
The onus is, therefore, on governments and city officials to proactively protect their cities and their inhabitants from floods.
Some of the most forward-thinking cities are adopting a whole-city approach that combines investment in risk management measures, including increasing insurance take up, to build resilience and mitigate the economic losses caused by floods.
As Elizabeth Yee, vice president of resilience finance at 100 Resilient Cities, says: “Building a city’s resilience requires an integrated approach to understanding and responding to risk… By embracing resilience, cities are now assessing how to build multiple benefits from single interventions, especially as it relates to flooding.”
In China, the number of cities affected by floods has more than doubled since 2008. To manage this growing risk, officials are planning a series of ‘sponge’ cities, in which 80% of the city will absorb and reuse at least 70% of rainwater. Shanghai, Wuhan, and Xiamen are part of the 30-city project that will be completed by 2020. Strategies include building permeable street surfaces and green infrastructure that uses plantings to improve flood resilience.
Chicago in the US, which is predicted to have 40% more winter precipitation by the end of the century, is also investing in green infrastructure. Its 100 permeable pavements – or “green alleys” as they are known locally – allow water to pass through the pavements into the ground. As a result, 80% of rainfall is diverted away from the sewage system and prevents roads from flooding.
Jakarta, of which 90% lies below sea level, is taking a different approach. The city has plans to relocate more than 400,000 residents that live near its reservoirs and riverbanks as part of its climate adaption programme. It is also developing a defence wall to protect the city against floods caused by the sea in Jakarta Bay. Large lagoons will be built within the wall to cope with flooding from the 13 rivers in Jakarta.
Floods are increasingly straining city budgets, so many cities are using (re)insurance programmes as a key part of their flood-resilience strategies. Not only do claims payments help businesses and communities recover quickly after floods, insurers can also work with policyholders to ensure risks are minimised before floods occur. Transferring the costs of flood damage from the public purse to private capital markets enables governments to invest in greater resilience instead of paying to rebuild.
From sponge cities to permeable pavements, cities are increasingly taking their vulnerability to flood risk seriously, and are adopting resilience strategies to help minimise the potential impacts of flooding on their economies and communities.
 according to a paper by the European Academies’ Science Advisory Council (Easac)
 according to a C40 Cities study, https://c40-production-images.s3.amazonaws.com/other_uploads/images/1789_Future_We_Don’t_Want_Report_1.4_hi-res_120618.original.pdf