Channel in the U.S. through which the James , Elizabeth, and Nansemond rivers flow into Chesapeake Bay .
About 4 mi (6 km) wide and 40 ft (12 m) deep, it has been an important military base since colonial days. In 1862 it was the scene of the Battle of the Monitor and Merrimack . The port cities of Newport News , Norfolk , and Portsmouth comprise the Port of Hampton Roads, one of the busiest U.S. seaports.