View Current Issue. Chesapeake Bay Facts and Figures. How the Bay Benefits Marylanders Rivers, streams, and aquifers supply clean drinking water to millions of state residents. Crab, striped bass, oyster, and other fisheries support the livelihood of commercial watermen. Marshes buffer shorelines against storms and flooding.
Wetlands, forests, and shorelines provide habitats for diverse plant and animal species. Beaches and other waterfront attractions draw tourists to Maryland. Plus the District of Columbia. It loops around 11, miles of shoreline. And where does all that water come from? Try the or so rivers and streams that dump into the Chesapeake. Also the Atlantic Ocean, which flushes salt water in through the mouth of the Bay. But there are many more storied tributaries, too, including the Patuxent, Choptank, and Pocomoke rivers in Maryland.
The Chesapeake is home to 29 species of waterfowl and is a major resting ground along the Atlantic Flyway. Every year, an estimated one million waterfowl winter in the Bay region. The Bay produces about million pounds of seafood per year. Since colonial times, the Bay has lost half of its forested shorelines, over half of its wetlands, nearly 90 percent of its underwater grasses, and more than 98 percent of its oysters.
The rest drains into the Bay from an enormous 64,square-mile watershed. You could live more than miles from the Chesapeake Bay and still be in part of its watershed. There are about major rivers and streams in the Bay watershed. The Susquehanna River provides about 50 percent of the fresh water coming into the Bay—an average of 19 million gallons of water per minute.
The ratio of land area drained by watershed to the volume of water in the Bay is This is the largest land-to-water ratio of any estuary in the world—ten times greater than its closest rival, the Gulf of Finland. Located beneath the mouth of the Chesapeake Bay running from underneath the tip of the Delmarva Peninsula near present-day Cape Charles, Virginia , across the Bay to Norfolk, Virginia, the roughly circular crater is twice the size of Rhode Island 2, sq mi [6, sq km] and nearly as deep as the Grand Canyon 0.
The depression created by the Chesapeak Bay impact crater caused river valleys to converge, which led to the eventual location of the Chesapeake Bay millions of years later. Ice sheets that covered the poles and Canada some 2 million years ago periodically pushed their way into the present-day United States. The ice was a major cause of changing sea levels: sea level rose as ice melted and fell as the water froze and more ice formed.
Water from the melting ice sheets fed the ancestral Susquehanna River, giving it the power to move massive amounts of sediment as it cut its way to the coast. As glaciers and sea level adjusted, so did the rivers. During glacial times lower sea level , rivers had to work their way across the exposed continental shelf to dump their sediment loads into the ocean. These rivers travel across an important geologic feature, the fall line, which marks the transition from Coastal Plain to Piedmont.
Geologically it represents the change from the softer sedimentary rock and unconsolidated sand and gravels of the Coastal Plain to the harder metamorphic rocks of the Piedmont core of the ancient Appalachians.
Rapids and waterfalls visually mark the fall line, where rivers flow off the topographically high rocks of the Piedmont and onto the flat, softer sediments of the Coastal Plain. These fall lines were important to later settlement patterns. The Potomac is the longest and has the largest watershed.
The enormous watersheds of these rivers produce huge flows of freshwater, which cause the western half of the Bay to be less salty, more silty, cluttered with woody and other vegetative debris, and generally more active than rivers on the eastern side. See a larger image of the rivers to the Bay.
The eastern rivers of the Chesapeake Bay are quite different from those in the west. These eastern rivers are not particularly long, do not collect freshwater from large drainage areas, and are tidal for most of their length. Because they contribute only a fraction of the water produced by the western rivers, the eastern half of the Bay is saltier, slower moving, more given to marshes, and more productive of saltwater plants such as submerged aquatic vegetation.
At the end of the last glacial stage, some 15, years ago, a great meltdown began and sea level rose relatively rapidly. During this period, the lower Susquehanna River basin started to fill up with seawater. Rising sea level moved up into the river, "drowning" it. By 10, years ago, the main channel of the ancient Susquehanna River valley was flooded and became a narrow estuary. Between 6, and 7, years ago, the rate of submergence began to slow, and the Chesapeake Bay took on its characteristic drowned-river-valley shoreline pattern.
Sea level at that time stood approximately 30 feet 9 m lower than the present level. During periods of high sea levels, the Delmarva Peninsula, the Chesapeake's "Eastern Shore," lengthened into a major barrier spit. The significant phase of forming the peninsula occurred in the early or middle Pleistocene period 1.
The creation of the Accomack spit protected the western shoreline of the Bay from the ocean's power for the first time, which was important to the formation of the Bay. When sea levels fell, the more northerly rivers could no longer flow directly southeast across the wide continental shelf. The emerging rivers were diverted southward around the tip of the lengthened peninsula.
The diverted river systems progressively joined the next river to the south and excavated a new channel. The pattern of lengthening the Delmarva Peninsula during sea-level highs and diverting all the western rivers into the dominant Susquehanna River continued until the modern Chesapeake Bay formed. Erosion, transportation, and deposition of sediments are constantly changing the Bay's shorelines. Currents and tides erode and smooth peninsulas and headlands and deposit materials in other parts of the Bay.
Rivers transport sediments and deposit them at the mouths of tributaries and along margins of the Bay, forming broad, flat deposits of mud and silt. These natural causes of sedimentation are often accelerated by human activity. By the mids, as farmers cleared more and more land for agriculture, sedimentation filled some of the navigable rivers used for travel. For example, Joppatowne, Maryland, once a seaport, is now more than 2 miles 3 km from water. The clearing of forests and other impacts of population growth continue to alter the Bay's landforms and increase sedimentation.
Sea-level rise has also changed the landscape. Many of the islands that existed in the Bay during colonial times are now submerged. For example, in the early s, Poplar Island in Talbot County, Maryland, encompassed several hundred acres. Today, a chain of small islands is all that remains of the original Poplar Island. Explore This Park. Info Alerts Maps Calendar.
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