Why London Floods

Herta Gatter, Town Planner, asks why the capital suffers and how a soft legacy of permeable green spaces helps to reduce flooding.

Last summer almost a month’s worth of rain fell in one 24-hour period at St James’s Park, making it the second wettest July since records began in 1912. Climate breakdown and increasing urbanisation both contribute to flood risk, so it is no wonder that a global city like London faces increasingly extreme weather conditions and the consequences that go with it. As more land is developed with roads and buildings, we simply must find places for water to go.

Victorian engineering directed the city’s waterways into the drainage systems. While this was a successful strategy to contain unpleasant odours and keep land available for building, the present levels of densification of areas together with climate change means that the infrastructure cannot cope with large amounts of water; quite simply, heavy rainfall increases the stress on an already overburdened city drainage system.

The Thames Barrier
by Rocco Dipoppa
The Thames Barrier
by Rocco Dipoppa

Climate change also means a rise in sea levels, so tidal rivers such as the Thames greatly increase the risk of flooding. The Thames Barrier is an incredible buttress which has protected London from tidal flooding since the 1980s, but it requires further improvements to continue protecting the city. We need to find more solutions.

Aerial photo of the Thames in London, UK, facing East.
Aerial photo of the Thames
by Peter Laskowski

To keep our cities safe we need to learn from nature; we must create opportunities for water to drain away through the land, nourishing plants, or recycling it for other purposes, rather than relying on antiquated drainage systems. Sustainable drainage systems (SuDS) are key to flood alleviation and surface water management. These nature-based features manage water across the built environment and can be incorporated into streets, parks, playgrounds and even building facades. They also provide green space for citizens to enjoy – and increase biodiversity.

Our designs for Cornmill Gardens and Ladywell Fields in Lewisham created opportunities for rainwater to flow away into rivers. Green spaces are cheaper to install than flood defences and they support the health and wellbeing of local communities. When we plan and design these places, we aim to leave a ‘soft’ legacy behind us and ensure that every plot is more green and more permeable than before.

Increasingly boroughs across London require developers to think seriously about managing water and flooding in their proposals. The mayor has introduced an ambitious new policy, called the Urban Greening Factor, which requires green space to form a fundamental element of all new development to contribute to flood mitigation. This is a step forward but a better managed and more holistic approach is still needed. The Dutch have extensive experience designing for flood risk, together with a dedicated governmental water management agency supported by a network of locally elected bodies. Our Rotterdam studio is sharing this knowledge to help achieve urban flood resilience.

Solutions start at micro-level and end at macro-level. Small actions can make a big difference. Understanding how we must change our lifestyle comes first. Considering how the economy affects the way we plan new places is next. Designing cities to reduce the need for cars, building on greenfield land and allocating responsibilities is imperative. We must collectively continue to raise awareness and support evidential shared learning for nature-based interventions. As severe weather events look set to become the norm, collaborative working between all parties will be key to safeguard the city.