Interesting. Earlier while listening to the news about the floods in Houston, I thought the city must be so paved over everywhere to accommodate all the cars, that the water has nowhere to go. Of coures, a big storm like this is unusual but I imagine not much thought has been given to sponge cities in places like Houston.
I posted an article by an expert on the subject at the Hurricanes thread at the weather page. Yes, that is one of the major problems, in an area where there were a lot of wetlands (Texas must have an extremely varied climate!)
Paris has been making an effort to vegetalise the roofs of housing projects and schools, but I personally am not yet convinced that it will make much of a difference. Paris is a city of traditional zinc roofs, and those buildings will probably always represent more than 90% of the roofs in the city.
Cities with a lot of new construction are another matter.
That is one reason China seems to be the world leader in this matter.
You can't do much greening of traditional Parisian roofs, but actually the city has taken other steps towards greening. Of course so much of Berlin was destroyed in the final phase of the Second World War...
Another problem with greening old buildings, in Paris or in other European countries, is the extra weight on the roofs that would be too heavy for the buildings' structures. As Lagatta says, since parts of Berlin were destroyed, then new buildings can be conceived to bear heavy roofs.
From the video, greening roofs is not the only solution. Keeping green areas in cities should be a priority, not paving everything over to make space for more cars.
Paving over is something that's frequently mentioned in the UK as a contributor to drainage problems in big cities, as well as more general ecological problems ( no "corridors" for insects and other wildlife as front gardens become parking spaces). But major flooding here comes down to building on flood plains, reduction of trees and increased land drainage upstream. And there are arguments about embankmenting and dredging as shifting the problem downstream - maybe flood meadows en route slow up the flood. But I doubt if anything could deal with a couple of months' rain in a few hours concentrated on a limited space, as here.
greening roofs is not the only solution. Keeping green areas in cities should be a priority, not paving everything over
That's such an important point. Greening roofs and the sides of buildings aYore dramatic solutions requiring expert planning and engineering. But maintaining empty lots as meadows, creating green parks, planting trees are relatively simple things that could be immediately implemented by cities.
major flooding here comes down to building on flood plains, reduction of trees and increased land drainage upstream. And there are arguments about embankmenting and dredging as shifting the problem downstream - maybe flood meadows en route slow up the flood.
Mankind has always settled on floodplains, but the moment we moved away from disposable houses riverside living became impractical. You don't just describe your area, but the history of the state of Louisiana, for instance.
The sponge city concept should open up dialogues about how cities can identify and then plan and budget to address existing problems.