With Henri hitting the northeast, I was thinking about that and how when Elsa hit that the subway tunnels flooded. Do they pump it out or something?
In: Engineering
There is a book titled, The World Without Us, that goes into the inner workings of this pretty descriptively. Worth a read
It is pumped out from the lowest points, floods happen when the amount of water coming in exceeds the capacity of the pumps.
I was in New York when the steam vents exploded near Grand Central station, because a flash flood got into the vents.
Subway tunnels indeed have pumps to remove excess water. If the flooding is too great, certain lines may have to be shut down temporarily.