Here is a relatively simple short term solution for how an older city can handle intense rain without having its sewer system overflow onto the streets or having to inject raw untreated sewage into the local rivers. It costs $ but not that much money. As I understand it, these inflatable devices create dams within the sewer system and can hold smelly water until the water treatment system can treat the flow of waste water.
This is an example of how new ideas help an old city adapt to new climate challenges. This is our future.