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).
Washington Dulles International Airport IAD is the larger of two major Washingon, D.C. airports and handles both domestic & international air traffic. (While Dulles Airport is actually situated in Virginia, Reagan National Airport is within short reach of the Nation's capital Washington D.C.).