Can floating islands, porous sidewalks save NYC from floods?
Renowned landscaped architect Diana Balmori envisions a new New York that can withstand future disasters
Q: How does it stay in place if it's floating?
A: You have to anchor it and that is a complicated thing that has to be engineered. We have just actually launched two test ones, one in the Delaware River and one in the Gowanus Canal in Brooklyn. In the Delaware River we are testing the ability of this layer of plants to create habitats, habitats for all kinds of insects, birds, fish, etc. And the one in Gowanus is to test what we call phyto-remediation, the ability of plants to take certain chemicals out of the water.
Q: Would they get rid of pollutants? Would they clean the water?
A: Exactly. And what we want to see is which work well and which don't.
Q: When I think "marsh,'' I don't necessarily think I want one of these in my front yard.
A: I know. The marsh in this case would be on a floating island very clearly demarcated and so you have control over which area it occurs in. But I have to remind you that the richest environment in the whole world in species diversity is the marsh, between water creatures and insects, birds etc., it's the richest per square inch of all the environments on earth. Marshes are really a cauldron of life. The marsh can be seen as a defensive system but these islands can be really used for urban agriculture and they could also be public space.
Q: Has any city tried them?
A: There are lots of examples of floating islands that have been done as a traditional agricultural form. It exists in Mexico, it exists in Bangladesh, Bolivia. So it's not an invention but it is an invention for the scale of the use I'm proposing, an urban scale. I'm interested in the aesthetic side too. I think they can be very beautiful.
Q: You've said that the city needs to become more porous. What does that mean?
A: It means that the city absorbs the water that comes down on it. We have made it totally impossible to drain anything through pipes because the whole surface of the city is impermeable. It's impermeable on the roofs, it's impermeable on the sidewalks, it's impermeable on the streets and therefore we have to gather all that water, put it in a pipe and throw it out into a river. And when we have a storm, we increase the speed of the water in the rivers which produces erosion of the shores of rivers and they do much more damage at a greater speed.
Q: So how do we make the city more porous?
A: There's all kinds of new pavements that are porous. Porous sidewalks, yes. There are systems by which the edges of streets become porous, they are made more into rain gardens and collect water. Parking lots have also devised ways of having these systems of rain gardens that collect the water to one side and it's absorbed through the plants and put back into the atmosphere just like with the green roof.
Q: You're envisioning the city with all green roofs, with floating marshes around it, with porous sidewalks, with parking lots and street edges that have gardens so that they'll take in all the water. Who's paying for this?
A: Well, there's a very good question. The forms of protection for the city in the forms of dams and flood walls cost many, many billions. But we're talking about something that's incredibly inexpensive. Plants happen to be the cheapest of all building materials. The systems by which we pave streets have on the one hand a municipality paying for them and on the other hand each individual owner or each individual building has to pay for their particular pavement. But it's the city that needs to find the instruments for doing this because it's the city that benefits. The city of Seattle, for example, has created this incentive for putting green roofs because it has figured out that it's cheaper to make green roofs in the whole city than to expand the whole drainage system. Instead of major infrastructure changes you're going to be able to put a much simpler and cheaper system in place and that's what's going to make it happen.