Humans need water, and civilisation needs a lot of it. 90 % of cities are built in flood plain because until relatively recently (~200 years or something?) it w

Humans need water, and civilisation needs a lot of it. 90 % of cities are built in flood plain because until relatively recently (~200 years or something?) it was impossible to have a city outside of flood plain. Now, we don't need to do it that way, but it still makes things more expensive.