Most modern cities have extensive drainage networks which include a whole series of covered and uncovered storm drains.
Check the maps of your area to find these – many concrete rivers are perfect for emergency egress through the city in a time of trouble.
Most people don’t know about these either – don’t just limit yourself to surface streets.
Physically inspect these now to find out where they go before disaster strikes, and have a plan to move through them. Obviously you wouldn't want to be in these "drainage" areas during heavy rain or flooding.