The diagram shows this better than I can explain it. At a gage height of 1 foot, our stream has the amount of water (flow) represented by the blue area. Let's say it rains and the water rises to 2 feet. The additional flow is represented by the green area.
Closest Airport to Washington, D. C., DC. The closest airport to Washington, D. C. is Ronald Reagan Washington National Airport (DCA). Distance from Ronald Reagan Washington National Airport to Washington, D. C., DC is 4,8 kilometers (3,0 miles).
Dulles Airport is just over 60 miles from downtown Baltimore. A taxi between Dulles Airport and BWI Airport is quoted at about $120 (before tip) on the Dulles website. It would be more to downtown Baltimore.