Flooding
Urban Flash Flooding Guide: Streets, Underpasses, Storm Drains, and Fast Runoff
Why cities can flood quickly during heavy rain, how pavement and drains change runoff, and why underpasses and low roads are dangerous.
Quick answer: Urban flash flooding happens when heavy rain falls faster than pavement, gutters, drains, and streams can move water away.
Why cities flood fast
Pavement prevents water from soaking into the ground, so runoff moves quickly into streets and drains.
Leaves, debris, construction, and overwhelmed drainage can worsen flooding.
Danger spots
Underpasses, low roads, parking lots, basements, and small creeks can fill quickly.
Water depth is hard to judge from a vehicle.
Safety
Do not drive through flooded streets. Turn around and find a higher route.
Avoid walking through moving water because drains and holes may be hidden.