Waterworld: Learning to live with flooding

Cities worldwide are already taking up the concept of “greening,” using permeable paving, bioswales (shallow ditches filled with vegetation), street planting, roof gardens, and pocket parks. Green infrastructure benefits health and biodiversity, and can help combat rising CO₂ levels, heat island effects, air pollution and noise.

“Not only do they also provide a place for water to soak away,” says Fenner, “they can even create resources from water – such as generating energy from the water flow through sustainable drainage systems and providing places for amenity and recreation.”

All well and good but with a long list of potential blue–green choices, and an equally long list of benefits, how do cities choose the best options?

One of the major outputs of the Blue–Green Cities initiative is a toolbox for authorities, planners, businesses, and communities to help them decide. Using Newcastle University’s CityCat model, the team assessed how well green infrastructures performed in holding back surface flows, and used novel tracer techniques to follow the movement and trapping of sediments during intense storms. Then they mapped the benefits in a geographic information system (GIS) to identify physical locations that are “benefit hotspots.”

The tools were developed by evaluating the performance benefits of green infrastructure gathered from sites in both the United Kingdom and the United States. As part of a recent 12-month demonstration study in Newcastle, a Learning Action Alliance network was set up with local stakeholders that has, says Fenner, led to new opportunities that reflect the priorities and preferences of communities and local residents.

Now, Newcastle City Council, the Environment Agency, Northumbrian Water, Newcastle University, Arup and Royal Haskoning DHV have combined to be the first organizations in the country to explicitly commit to a blue–green approach, as recommended by the research. The hope is that other local and national organizations will follow suit.

Embracing resilience, as these organisations are doing, is vitally important when dealing with natural hazards, says Emily So, who leads CURBE: “We should remember that flooding is a natural process and a hazard we need to learn to live with. It is often the disjointed configuration of the built environment that results in it being a risk to the communities. Our aim should be to design to reduce the impact of, and our recovery time from, this natural hazard.”

Fenner adds: “Continuing to deliver an effective and reliable water and wastewater service despite disruptive challenges such as flooding is hard, but vital; it requires continuous and dramatic innovation. In the future, we will see fully water-sensitive cities, where water management is so good that it’s almost as if the city isn’t there.”

The Blue–Green Cities projectis funded by the Engineering and Physical Sciences Research Council (EPSRC), involves researchers from nine U.K. universities, and is led by the University of Nottingham. A parallel project, Clean Water for All, funded by EPSRC and the National
Science Foundation, connects the team with researchers in the United States.

Flood risk as a driver for change

While the Blue–Green Cities project focuses on urban drainage at times of normal to excessive rainfall,Ed Barsleyis more concerned with helping communities consider the consequences of extreme events.

“Floods are devastating in their impact and flood risk is often seen as a burden to be endured,” says Barsley, “but future proofing and planning for resilience can and should be used as a driver for increasing the quality of buildings, streets and neighborhoods – a chance for exciting change in our cities.”

As a case study, Barsley is using the village of Yalding in Kent, which has endured physical, economic and psychological impacts as a result of flooding.

He looked at how each house in the village prepared for and was affected by its most recent flood, its location and building material, and even its millimeter threshold height; and then he looked at future flood risk scenarios. The result is a methodology for assessing resilience that can be used to help inform and plan for adaptation, and is transferable to other communities large or small across the United Kingdom and worldwide.

“When we communicated the risks to the community, we found that resilience means different things to different people. Understanding priorities can help them tailor their own strategy to be contextually appropriate,” explains Barsley, who is special advisor on flood risk in the South East to Greg Clark MP, Secretary of State for the Department for Communities and Local Government.

For homes in which resistance measures like flood barriers will be overcome, one option might be to regard the lower floor as a sacrificial space – an area that can be flooded without disrupting waste, power or water. In Yalding, there are examples of homeowners who have done just this and added an extra story to their homes.

“I’d like to see resilience rewarded and for us to begin to live with water in a different manner. Embedding long-term resilience has huge potential for creating vibrant and enriching spaces.”