The Geography of the Chesapeake Bay

The Bay’s mainstem stretches about 189 miles from its confluence with the Susquehanna River in Havre de Grace, MD to its mouth near Norfolk, VA. At its narrowest point near Annapolis, Maryland, the Bay measures only four miles wide, while near the mouth of the Potomac River in Virginia, it spans nearly 30 miles. Home to over 3,600 species of plants and animals, as well as more than 15 million people, the Bay watershed is an incredibly complex ecosystem in need of improvement.

As the drowned river valley of the Susquehanna River flooded by melting glaciers over 12,000 years ago, the Chesapeake Bay averages only 21 feet deep. However, the majority of the Bay measures less than six feet deep. At its deepest point, near Kent Island’s Bloody Point Hole, the Bay measures 174 feet deep.

The nine largest rivers flowing into the Bay and supply over 93% of its fresh water include the Susquehanna, Potomac, James, Appomattox, Pamunkey, Rappahannock, Mattaponi, Patuxent and Choptank Rivers. The Pamunkey and Mattiponi converge at West Point, VA to form the York River. Alone, the Susquehanna River provides over half of the freshwater in the Bay.

The Ecology of the Chesapeake Bay

Native Americans first named the large body of water we now call the Chesapeake Bay, “Chesepiooc” or "Great Shellfish Bay", for its bountiful supply of crabs, oysters and clams. While it is among the shallowest of bays, it is the largest and yields more fish and shellfish than any of the other 130 estuaries found in the United States.

The Bay’s warm, shallow water and its mix of fresh and salt water create a variety of habitats that support many divergent species, including bald eagles, ospreys, shad, blue crabs, oysters, finfish, sharks, geese, land and sea turtles and eels.

More than 3,600 plants, animals and fish in the Bay’s 64,000 square mile watershed, including many rare and locally endangered species. Fifty major tree species, more than 300 species of fish and 200 species of birds live in the watershed as well. As major resting point on the Atlantic Migratory Bird Flyway, Chesapeake Bay and its 11,684 miles of shoreline hosts over a million wintering waterfowl each year.

Chesapeake Bay blue crab, Callinectes sapidus

Chesapeake Bay is known around the world for its most notable resident, the blue crab. More than one-third of blue crabs consumed in the United States come from the Bay’s waters. In addition to crabs, the Chesapeake is also known throughout the world for its oyster harvest as well. Due to overharvesting and disease, however, oyster population have declined to about one percent of historical levels.

As a large, warm, shallow, tray shaped estuary, the Bay acts as a nursery for crabs, oysters as well as many other species of fish and shellfish. Underwater grasses or SAV (submerged aquatic vegetation) provide food, shelter, oxygen and important habitat for the young marine creatures.

Home to more than 300 species of fish, the Bay hosts 32 year-round species. Some species, including flounder, bluefish and menhaden, come to the Bay in late spring and summer to feed, while other species including eels and shad use the Bay and its rivers to reproduce and then return to the sea. In fact, between 70 and 90 percent of Atlantic striped bass are born in the Bay.

For more in depth information about the Chesapeake Bay, visit the Chesapeake Bay Program website at www.chesapeakebay.net