How should cities respond to the threat of flooding? I think sometimes small, simple interventions can be the most effective. They can be implemented faster, more cost effectively but must be in response to specific needs.
The answer commonly to flooding or rising sea levels is often to try and stop water entirely. While this is appropriate in some cases (such as for critical and immovable infrastructure) it is very difficult and expensive to design for the worst-case scenario. Yes, you could build an enormous (and enormously expensive) flood barrier. But it can blight the appearance of the waterfront and only be needed occasionally.
This is why I believe we also need to think more about resilience – not in terms of stopping the threat – but in terms of recovery and getting back to normal quickly after an event. This is the approach we’ve applied in some of our recent work in Manhattan.
Our competition-winning design for the FAR ROC area of waterfront included a more considered solution with multiple elements combining to address specific issues. Flood relief channels, a hinged boardwalk that rises and falls with the water level and pathways for emergency vehicles were addressed and interwoven to provide the final solution. Local hubs provide shelter in the event of a flood. And the elevated housing includes ground floors that ‘fold up’ to allow floodwater in and out quickly without causing structural damage.
Similarly, we designed the new Hunter’s Point South park with streetside stormwater planters and bioswales to filter water pollution and reduce runoff. A porous pavement covering 33% of the sidewalk area also limits the runoff sent into storm sewers, and these are now separate from sanitary sewers. The cost differential between hardened barriers and green infrastructure can be a factor of ten, or more – but offer a very different approach to to the problem.
These features were tested during Superstorm Sandy and proved their worth. Sandy caused only minimal damage to the park, buildings and infrastructure (which were under construction at the time) which recovered quickly post event.
I believe that these lessons on the benefits of simple, small interventions could be applied to communities around the world that find themselves increasingly affected by flooding. However, it does require a fundamental mind-shift in approach. We must get used to living with the realization that some inundation is possible, but similarly we have a right to expect the cities and towns have a plan to recover and restore quickly with no peril to the community or emergency service providers. We are beginning to see pioneering agencies and authorities adopting this approach with great success. Chicago have been advocating green alleys and streets for some time with great success, as have New York City with the implementation of their ‘Green Infrastructure’ Program.
This is why we began the projects in Manhattan by working with communities to ensure they understood the implications of choosing to live on the waterfront, and the impracticality of eliminating flooding altogether.
Flooding will increasingly be a part of our lives and inevitably become a fact of life in many cities, but it’s one I believe that high-quality design can help us live with and overcome.
This feature is written by Tom Kennedy and originally appeared in Arup.