Amsterdam is home to 45,000 sq metres of ‘blue-green’ roofs, which absorb rainwater and allow it to be used by building residents to water plants and flush toilets

Devastating deluges around the world point to the metropolis of tomorrow: the “sponge city.” Think more parks and fewer parking lots.

Cities are still catching up with the natural protection systems that can make a difference when engineered infrastructure is overwhelmed by severe weather.