One smart thing cities everywhere should be doing right now is refactoring their landscapes to capture the water from these downpours (and hurricanes). As far as I know, there is only one city in India that has done this -- rainwater is captured and diverted to ground wells.
Everywhere else just lets the water run back into drainage, rivers, and bays, losing the freshwater to runoff and salt.
There is so much we need to change and so little interest or time.
@wion A big part of the flooding problems is that the artificial systems can't cope with the sudden volume of water.
I can't speak for France but I expect it's similar to Germany, where planning regulations have long existed to limit the amount of sealed (tarmac, paved, built over) surface on a site. Provided the soil is permeable, water should find its way to the groundwater without artificial channelling. Special soakaways help too, as do natural flood regulation methods (e.g. meadows)...
There you are. ;)
Right, so one tactic city planners need to be thinking about is retrofitting those artificial containment systems if they can't handle the way nature now delivers. At the very least, improve channeling the water more effectively to the natural tables.
We can't really talk about it at a national level. Terrain is radically different across kilometers. Topology, geology, etc. And cities like Paris are basically concrete jungles that drain into sewers.
I'll have to find the article about the Indian city that dealt with this. They made it clear a lot of engineering was needed to improve how monsoon water was used more effectively.
Yes, meadows and whatnot are great. But even in open terrains like that water tables are drying up. Look at the San Fernando Valley in California, a critical farming region that most of the US and some other nations rely on. The water there is almost gone.
Capture elsewhere and ship it. But don't lose it!
@wion Singapore captures most of its rainwater in reservoirs.
Here's a webpage about it from Singapore's Public Utilities Board [ https://www.pub.gov.sg/watersupply/fournationaltaps/localcatchmentwater ].
Thank you. Good to hear.