[gucci-on-fleek]

> naively I would expect the wastewater infrastructure to be overbuilt enough to manage larger than normal rains, which are usually several times over typical household wastewater production

It depends on the city—some cities do indeed handle rainwater with the normal sewer system, but most have an entirely separate system for rainwater [0]. But either way, if you pave more roads, you're always going to have more rainwater to deal with, regardless of which system of pipes you use.

[0]: https://en.wikipedia.org/wiki/Storm_drain#Combined_sewers

[tpm]

1. The parent was mentioning densification - that doesn't automatically mean more roads.

2. It's not just roads but also roofs etc., is it common to drain the house roof into a different system than the rest of the house? Of course in a house with a large lot you can drain into a garden or whatever but that's not possible in densely built areas. In our city it all ends up in one system but of course we've had a sewer system since the middle ages or so.

[gucci-on-fleek]

> 1. The parent was mentioning densification - that doesn't automatically mean more roads.

Yes of course, I forgot where I was in the thread, sorry.

> 2. It's not just roads but also roofs etc., is it common to drain the house roof into a different system than the rest of the house? Of course in a house with a large lot you can drain into a garden or whatever but that's not possible in densely built areas. In our city it all ends up in one system but of course we've had a sewer system since the middle ages or so.

I'm mainly familiar with smaller buildings, but I know that it's illegal to drain rainwater into the main sewer system, so presumably the bigger buildings are hooked up to the storm sewer system.

The climate here is kinda bizzare though: it's fairly common to get a few days of +15°C while there's still 3' of snow on the ground, and as you can imagine, that causes a ton of runoff from all the melting. And very little here is more than a century old, so everything is comparatively modern.