In the US for example, average annual flood losses are predicted to increase by 26.4% from US$32 billion to US$40.6 billion in less than 30 years while in Europe, the cost of flood damage is set to rise to over £1 trillion per year by 2100. These trends are more severe in countries across the Global South that are not only geographically more vulnerable to climate change but often cannot afford to adapt at the pace necessary.
By 2050 7 out of 10 people in the world will live in cities and the direct and indirect impact of the climate crisis is becoming a major concern for the planet’s urban centres. Surface water flooding is a key issue for cities as hard surfaces such as roads, buildings and pavements prevent rainwater from being absorbed. During extreme rainfall, this can overwhelm drainage systems and increases the likelihood, extent and impact of flooding. Urban residents are also more vulnerable to precipitation-triggered landslides – a key challenge for cities where rapid, informal urbanisation has contributed to localised deforestation, weakening slopes and leaving residents vulnerable to landslides during extreme rainfall events. The indirect impacts of flooding such as supply disruptions and mass migration will also have significant impacts on cities.
In particular, extreme weather events disproportionately impact poor and marginalised communities and flooding is no different. Lower income residents are more likely to live in flood-prone areas and often have little protection and few resources to recover from floods. For this reason, extreme flood events are set to exacerbate poverty and inequality in cities across the world.
Flooding events are having severe consequences for communities, economies and infrastructure. In light of this local authorities, cities and communities across the world are developing innovative adaptation infrastructure strategies that increases resilience to extreme weather, reduces emissions, boosts biodiversity, improves wellbeing and creates new economic opportunities.
Nature-based solutions to urban flooding: Flood Parks
To date, the story of modern engineering has been hard infrastructure solutions attempting to contain and prevent natural processes. However, as costs increase and weather becomes more extreme, there is growing interest in solutions that work with nature. These sustainable approaches are broadly labelled ‘Nature-based Solutions’ (NbS). One example, particularly in cities prone to floods, has been “flood parks.” These green spaces are explicitly designed to store water during flood events, slowly releasing it during dry periods. This mitigates the damaging impacts of extreme weather events, cools urban heat islands, relives pressure on drainage systems, provides valuable ecosystem services, and gives citizens space to relax, socialise, exercise, work or study.
Flood parks can be developed by cities along rivers or coastal areas and can also be located upstream or on floodplains to absorb the impact of storm surges and flood waters. Flood parks can also form part of Sustainable Urban Drainage Systems (SuDS) by being integrated with rain gardens, swales, new and existing wetlands and retention ponds to capitalise on the mental, social, physical and environmental benefits of blue-green infrastructure within often lonely and grey urban environments.
One critique of NbS such as flood parks is that their popularity can drive up local property prices. This ‘Green Gentrification’ continues to be a source of conflict in many urban communities and highlights the importance of considering equity throughout a project’s lifecycle to avoid pricing out the communities that are intended to benefit.
Across the world local authorities are investing in green infrastructure to mitigate the impact of flooding and deliver a range of important co-benefits for urban residents. The following four case studies highlight urban flood park projects in New York City, Dakar, Copenhagen and across China.