Permeable cities: Adapting to climate change

Yet, while access to water is central to economic growth and human wellbeing, the relationship between cities and their water resources can be a volatile one. This decade to date, extreme weather events including hurricanes, typhoons, cyclones, flooding, and severe rainfall have caused an average of $227 billion in economic damage per year, up 61% from the previous decade. By 2050, rising sea levels could increase this cost to $1 trillion per year – or more, depending on the success of climate change policies.

Global floods and extreme rainfall have increased at the same time as cities such as Cape Town and Chennai have suffered from drought and water scarcity. Cities trapped between these forces face a mounting challenge. Already, cities play a central role in mitigating climate change, accounting for 60-80% of all energy consumption and 70% of global emissions. Investment in clean energy, sustainable transport systems, energy-efficient buildings, and smart grids are essential to reducing urban footprints on our environment. With climate change inevitable, however, cities must also evolve to become more resilient to extreme weather and drought.

One approach to adapting to rising sea levels and extreme weather can be referred to as the “steel and concrete” solution. In the Netherlands, the Delta Works are a network of dams, sluices, locks and storm surge barriers, designed to protect low-lying lands and declared one of the Seven Wonders of the Modern World. Cities around the world are drawing on this example for inspiration. In New York, a $10 billion plan would construct a U-shaped system of flood defences around Manhattan, consisting of barriers, parks and a coastal extension of up to two city blocks. 

An alternative approach focuses on the ability to capture and re-use rain water. In China, a 16-city pilot programme is exploring the concept of “sponge cities”, looking to develop more porous infrastructure through green spaces, drainage systems and permeable roads. These cities are looking to reduce concrete pavement with greener alternatives, and aim to capture and re-use as much as 70% of incident rainfall, serving both to mitigate floods and manage the risks of drought. Initially piloted in China, the concept is now also being implemented in Berlin and keenly watched by cities around the globe.

They should not wait too long – climate adaption is best done early on, as part of urban planning and development, rather than retroactively. We should start early, and boldly. At present, only 5% of climate change investment is spent on adaptation activities, while funding requirements may increase to $500 billion per year by 2050. As an investment it is a good one. The Global Commission on Adaptation argues that investing $1.8 trillion in strengthening infrastructure, early warning systems, water resources and other key areas would accrue benefits amounting to $7.1 trillion – a four-to-one return.