From Fairfax County Fire and Rescue Department:
Flash flooding of roads, streams, and other low-lying areas during heavy and prolonged rainfall can be dangerous. This is especially true for motorists attempting to negotiate a roadway that cannot be easily seen because of high water and limited visibility. Flooding due to high rainfall and swollen streams can take its toll on the unsuspecting driver. The Fairfax County Fire and Rescue Department offers the following safety tips when flooding is forecasted and locations of past flooding areas.
Never drive through a flooded roadway; the depth, current, and condition of the road are all unknowns and can be deadly.
If you come to a flooded area while driving, stop and take an alternate route.
If your vehicle stalls on a flooded road and water is rising, get out of car, call 911, and move to higher ground.