chesapeake bay watershed

The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the Eastern Shore of Maryland / Eastern Shore of Virginia and the state of Delaware) with its mouth of the Bay at the south end located between Cape Henry and Cape Charles. With its northern portion in Maryland and the southern part in Virginia, the Chesapeake Bay is a very important feature for the ecology and economy of those two states, as well as others surrounding within its watershed. More than 150 major rivers and streams flow into the Bay's drainage basin, which covers parts of six states (New York, Pennsylvania, Delaware, Maryland, Virginia and West Virginia) and all of District of Columbia.

The Bay is approximately long from its northern headwaters in the Susquehanna River to its outlet in the Atlantic Ocean. It is wide at its narrowest (between Kent County's Plum Point near Newtown in the east and the Harford County western shore near Romney Creek) and at its widest (just south of the mouth of the Potomac River which divides Maryland from Virginia). Total shoreline including tributaries is , circumnavigating a surface area of . Average depth is , reaching a maximum of . The Bay is spanned twice, in Maryland by the Chesapeake Bay Bridge from Sandy Point (near Annapolis) to Kent Island and in Virginia by the Chesapeake Bay Bridge–Tunnel connecting Virginia Beach to Cape Charles.

Known for both its beauty and bounty, the Bay has become "emptier", with fewer crabs, oysters and watermen (fishermen) since the mid-20th century. Nutrient pollution and urban runoff have been identified as major components of impaired water quality in the bay stressing ecosystems and compounding the decline of shellfish due to overharvesting. Restoration efforts that began in the 1990s have continued into the 21st century and show potential for growth of the native oyster population. The health of the Chesapeake Bay improved in 2015, marking three years of gains over a four-year period, according to a 2016 report by the University of Maryland. The bay is experiencing other environmental concerns, including climate change which is causing sea level rise that erodes coastal areas and infrastructure and changes to the marine ecosystem. These changes have already changed the coastline eroding islands like Holland Island or Long Island and threatening local infrastructure and economies.

Etymology

The word is an Algonquian word referring to a village 'at a big river'. It is the seventh-oldest surviving English place-name in the United States, first applied as ''Chesepiook'' by explorers heading north from the Roanoke Colony into a Chesapeake tributary in 1585 or 1586. The name may also refer to the Chesapeake people or the Chesepian, a Native American tribe who inhabited the area now known as South Hampton Roads in the U.S. state of Virginia. They occupied an area that is now the Norfolk, Portsmouth, Chesapeake, and Virginia Beach areas. In 2005, Algonquian linguist Blair Rudes "helped to dispel one of the area's most widely held beliefs: that 'Chesapeake' means something like 'great shellfish bay'. It does not, Rudes said. The name might have actually meant something like 'great water', or it might have just referred to a village location at the Bay's mouth."

Physical geography

Geology and formation

The Chesapeake Bay is an estuary to the North Atlantic, lying between the Delmarva Peninsula to the east and the North American mainland to the west. It is the ''ria'', or drowned valley, of the Susquehanna River, meaning that it was the alluvial plain where the river flowed when the sea level was lower. It is not a ''fjord'', because the Laurentide Ice Sheet never reached as far south as the northernmost point on the Bay. North of Baltimore, the western shore borders the hilly Piedmont region of Maryland; south of the city the Bay lies within the state's low-lying coastal plain, with sedimentary cliffs to the west, and flat islands, winding creeks and marshes to the east. The large rivers entering the Bay from the west have broad mouths and are extensions of the main ria for miles up the course of each river.

The Bay's geology, its present form, and its very location were created by a bolide impact event at the end of the Eocene (about 35.5 million years ago), forming the Chesapeake Bay impact crater and much later the Susquehanna River valley. The Bay was formed starting about 10,000 years ago when rising sea levels at the end of the last ice age flooded the Susquehanna River valley. Parts of the Bay, especially the Calvert County, Maryland, coastline, are lined by cliffs composed of deposits from receding waters millions of years ago. These cliffs, generally known as Calvert Cliffs, are famous for their fossils, especially fossilized shark teeth, which are commonly found washed up on the beaches next to the cliffs. Scientists' Cliffs is a beach community in Calvert County named for the desire to create a retreat for scientists when the community was founded in 1935.

Hydrology

Much of the Bay is shallow. At the point where the Susquehanna River flows into the Bay, the average depth is , although this soon diminishes to an average of southeast of the city of Havre de Grace, Maryland, to about just north of Annapolis. On average, the depth of the Bay is , including tributaries; over 24 percent of the Bay is less than deep.

Because the Bay is an estuary, it has fresh water, salt water and brackish water. Brackish water has three salinity zones: oligohaline, mesohaline, and polyhaline. The freshwater zone runs from the mouth of the Susquehanna River to north Baltimore. The oligohaline zone has very little salt. Salinity varies from 0.5  ppt (parts per thousand) to 10 ppt, and freshwater species can survive there. The north end of the oligohaline zone is north Baltimore and the south end is the Chesapeake Bay Bridge. The mesohaline zone has a medium amount of salt and runs from the Bay Bridge to the mouth of the Rappahannock River. Salinity there ranges from 1.07% to 1.8%. The polyhaline zone is the saltiest zone, and some of the water can be as salty as sea water. It runs from the mouth of the Rappahannock River to the mouth of the Bay. The salinity ranges from 1.87% to 3.6%. (3.6% is as salty as the ocean.)

The climate of the area surrounding the Bay is primarily humid subtropical, with hot, very humid summers and cold to mild winters. Only the area around the mouth of the Susquehanna River is continental in nature, and the mouth of the Susquehanna River and the Susquehanna flats often freeze in winter. It is rare for the surface of the Bay to freeze in winter, something that happened most recently in the winter of 1976–77.

The Chesapeake Bay is the end point of over 150 rivers and streams. The largest rivers flowing directly into the Bay, in order of discharge, are:
* Susquehanna River
* Potomac River
* James River
* Rappahannock River
* York River
* Patuxent River
* Choptank River

For more information on Chesapeake Bay rivers, see the List of Chesapeake Bay rivers.

Flora and fauna

The Chesapeake Bay is home to numerous fauna that either migrate to the Bay at some point during the year or live there year-round. There are over 300 species of fish and numerous shellfish and crab species. Some of these include the Atlantic menhaden, striped bass, American eel, eastern oyster, Atlantic horseshoe crab, and the blue crab.

Birds include ospreys, great blue herons, bald eagles, and peregrine falcons, the last two of which were threatened by DDT; their numbers plummeted but have risen in recent years. The piping plover is a near threatened species that inhabits the wetlands.

Larger fish such as Atlantic sturgeon, varieties of sharks, and stingrays visit the Chesapeake Bay. The waters of the Chesapeake Bay have been regarded as one of the most important nursery areas for sharks along the east coast.The National Aquarium
Sharks Among Us: Chesapeake Bay Species
. Retrieved on December 22. 2014 Megafaunas such as bull sharks, tiger sharks, scalloped hammerhead sharks, and basking sharks and manta rays are also known to visit. Smaller species of sharks and stingrays that are known to be regular to occasional residents in the bay include the smooth dogfish, spiny dogfish, cownose ray, and bonnethead.

Bottlenose dolphins are known to live seasonally/yearly in the Bay. There have been unconfirmed sightings of humpback whales in recent years. Endangered North Atlantic right whale and fin, and minke and sei whales have also been sighted within and in the vicinity of the Bay.

A male manatee visited the Bay several times between 1994 and 2011, even though the area is north of the species' normal range. The manatee, recognizable due to distinct markings on its body, was nicknamed "Chessie" after a legendary sea monster that was allegedly sighted in the Bay during the 20th century. The same manatee has been spotted as far north as Rhode Island, and was the first manatee known to travel so far north. Other manatees are occasionally seen in the Bay and its tributaries, which contain sea grasses that are part of the manatee's diet.

Loggerhead turtles are known to visit the Bay.

The Chesapeake Bay is also home to a diverse flora, both land and aquatic. Common submerged aquatic vegetation includes eelgrass and widgeon grass. A report in 2011 suggested that information on underwater grasses would be released, because "submerged grasses provide food and habitat for a number of species, adding oxygen to the water and improving water clarity." Other vegetation that makes its home in other parts of the Bay are wild rice, various trees like the red maple, loblolly pine and bald cypress, and spartina grass and phragmites. Invasive plants have taken a significant foothold in the Bay; plants such as Brazilian waterweed, native to South America, have spread to most continents with the help of aquarium owners, who often dump the contents of their aquariums into nearby lakes and streams. It is highly invasive, and has the potential to flourish in the low-salinity tidal waters of the Chesapeake Bay. Dense stands of Brazilian waterweed can restrict water movement, trap sediment and affect water quality. Various local K-12 schools in the Maryland and Virginia region often have programs that cultivate native bay grasses and plant them in the Bay.

History

Pre Columbian

The Chesapeake Bay has had a human presence for over 11,500 years. "Paleoindians," or the first humans in the Chesapeake Bay region, lived off the land by hunting game and living off the earth in small nomadic groups. Archeologists have also noted the presence of “foreign” stones in projectile points that came via trade from other parts of North America. For thousands of years, Native American societies lived in villages of wooden longhouses close to water bodies where they fished and farmed the land. Agricultural products included beans, corn, tobacco, and squash. Villages often lasted between 10 and 20 years before being abandoned due to local resources such as firewood running out or soil depleting. To produce enough food, labor was divided with men hunting while the women supervised the village's farming. All village members took part in the harvesting of fish and shellfish from the local bodies of water.
As time went on, communities around Chesapeake Bay formed confederations such as the Powhatan, the Piscataway, and the Nanticoke. Each of these confederations consisted of a collections of smaller tribes falling under the leadership of a central chief.

European exploration and settlement

In 1524, Italian explorer Giovanni da Verrazzano, (1485–1528), in service of the French crown, (famous for sailing through and thereafter naming the entrance to New York Bay as the " Verrazzano Narrows", including now in the 20th century, a suspension bridge also named for him) sailed past the Chesapeake, but did not enter the Bay. Spanish explorer Lucas Vásquez de Ayllón sent an expedition out from Hispaniola in 1525 that reached the mouths of the Chesapeake and Delaware Bays. It may have been the first European expedition to explore parts of the Chesapeake Bay, which the Spaniards called "Bahía de Santa María" ("Bay of St. Mary") or "Bahía de Madre de Dios."("Bay of the Mother of God") De Ayllón established a short-lived Spanish mission settlement, San Miguel de Gualdape, in 1526 along the Atlantic coast. Many scholars doubt the assertion that it was as far north as the Chesapeake; most place it in present-day Georgia's Sapelo Island. In 1573, Pedro Menéndez de Márquez, the governor of Spanish Florida, conducted further exploration of the Chesapeake. In 1570, Spanish Jesuits established the short-lived Ajacan Mission on one of the Chesapeake tributaries in present-day Virginia.

The arrival of English colonists under Sir Walter Raleigh and Humphrey Gilbert in the late 16th century to found a colony, later settled at Roanoke Island (off the present-day coast of North Carolina) for the Virginia Company, marked the first time that the English approached the gates to the Chesapeake Bay between the capes of Cape Charles and Cape Henry. Three decades later, in 1607, Europeans again entered the Bay. Captain John Smith of England explored and mapped the Bay between 1607 and 1609, resulting in the publication in 1612 back in the British Isles of ''"A Map of Virginia"''. Smith wrote in his journal: "Heaven and earth have never agreed better to frame a place for man's habitation." The new laying out of the "Captain John Smith Chesapeake National Historic Trail", the United States' first designated "all-water" National Historic Trail, was created in July 2006, by the National Park Service of the U.S. Department of the Interior following the route of Smith's historic 17th-century voyage. Because of economic hardships and civil strife in the "Mother Land", there was a mass migration of southern English Cavaliers and their servants to the Chesapeake Bay region between 1640 and 1675, to both of the new colonies of the Province of Virginia and the Province of Maryland.

American Revolution to the present

The Chesapeake Bay was the site of the Battle of the Chesapeake (also known as the "Battle of the Capes", Cape Charles and Cape Henry) in 1781, during which the French fleet defeated the Royal Navy in the decisive naval battle of the American Revolutionary War. The British defeat enabled General George Washington and his French allied armies under Comte de Rochambeau to march down from New York and bottle up the rampaging southern British Army of Lord Cornwallis from the North and South Carolinas at the siege of Battle of Yorktown in Yorktown, Virginia. Their marching route from Newport, Rhode Island through Connecticut, New York State, Pennsylvania, New Jersey and Delaware to the "Head of Elk" by the Susquehanna River along the shores and also partially sailing down the Bay to Virginia. It is also the subject of a designated National Historic Trail under the National Park Service as the Washington–Rochambeau Revolutionary Route.

The Bay would again see conflict during War of 1812. During the year of 1813, from their base on Tangier Island, British naval forces under the command of Admiral George Cockburn raided several towns on the shores of the Chesapeake, treating the Bay as if it were a "British Lake". The Chesapeake Bay Flotilla, a fleet of shallow-draft armed barges under the command of U.S. Navy Commodore Joshua Barney, was assembled to stall British shore raids and attacks. After months of harassment by Barney, the British landed on the west side of the Patuxent at Benedict, Maryland, the Chesapeake Flotilla was scuttled, and the British trekked overland to rout the U.S. Army at Bladensburg and burn the U.S. Capitol in August 1814. A few days later in a "pincer attack", they also sailed up the Potomac River to attack Fort Washington below the National Capital and raided the nearby port town of Alexandria, Virginia.

There were so-called " Oyster Wars" in the late 19th and early 20th centuries. Until the mid-20th century, oyster harvesting rivaled the crab industry among Chesapeake watermen, a dwindling breed whose skipjacks and other workboats were supplanted by recreational craft in the latter part of the century.

In the 1960s, the Calvert Cliffs Nuclear Power Plant on the historic Calvert Cliffs in Calvert County on the Western Shore of Maryland began using water from the Bay to cool its reactor.

Navigation

The Chesapeake Bay forms a link in the Intracoastal Waterway, of the bays, sounds and inlets between the off-shore barrier islands and the coastal mainland along the Atlantic coast connecting the Chesapeake and Delaware Canal (linking the Bay to the north and the Delaware River) with the Albemarle and Chesapeake Canal (linking the Bay, to the south, via the Elizabeth River, by the cities of Norfolk and Portsmouth to the Albemarle Sound and Pamlico Sound in North Carolina and further to the Sea Islands of Georgia). A busy shipping channel (dredged by the U.S. Army Corps of Engineers since the 1850s) runs the length of the Bay, is an important transit route for large vessels entering or leaving the Port of Baltimore, and further north through the Chesapeake and Delaware Canal to the ports of Wilmington and Philadelphia on the Delaware River.

During the later half of the 19th century and the first half of the 20th century, the Bay was plied by passenger steamships and packet boat lines connecting the various cities on it, notably the Baltimore Steam Packet Company ("Old Bay Line").

In the later 20th century, a series of road crossings were built. One, the Chesapeake Bay Bridge (also known as the Governor William Preston Lane, Jr. Memorial Bridge) between the state capital of Annapolis, Maryland and Matapeake on the Eastern Shore, crossing Kent Island, was constructed 1949–1952. A second, parallel, span was added in 1973. The Chesapeake Bay Bridge–Tunnel, connecting Virginia's Eastern Shore with its mainland (at the metropolitan areas of Virginia Beach, Norfolk, Portsmouth, and Chesapeake), is approximately long; it has trestle bridges as well as two stretches of tunnels that allow unimpeded shipping; the bridge is supported by four man-made islands. The Chesapeake Bay Bridge –Tunnel was opened for two lanes in 1964 and four lanes in 1999.

Tides

Tides in the Chesapeake Bay exhibit an interesting and unique behavior due to the nature of the topography (both horizontal and vertical shape), wind-driven circulation, and how the Bay interacts with oceanic tides. Research into the peculiar behavior of tides both at the northern and southern extents of the Bay began in the late 1970s. One study noted sea level fluctuations at periods of 5 days, driven by sea level changes at the Bay's mouth on the Atlantic coast and local lateral winds, and 2.5 days, caused by resonant oscillations driven by local longitudinal winds, while another study later found that the geometry of the Bay permits for a resonant period of 1.46 days.

A good example of how the different Chesapeake Bay sites experience different tides can be seen in the tidal predictions published by the National Oceanographic and Atmospheric Administration (NOAA) (see figure at right).

At the Chesapeake Bay Bridge–Tunnel (CBBT) site, which lies at the southernmost point of the Bay where it meets the Atlantic Ocean near Norfolk, Virginia, and the capes of Charles and Henry, there is a distinct semi-diurnal tide throughout the lunar month, with small amplitude modulations during spring (new/full moon) vs. neap (one/three quarter moon) tidal periods. The main forcing of the CBBT tides are typical, semi-diurnal ocean tides that the East Coast of the United States experiences.

Baltimore, in the northern portion of the Bay, experiences a noticeable modulation to form its mixed tidal nature during spring vs. neap tides. Spring tides, when the sun-earth-moon system forms a line, cause the largest tidal amplitudes during lunar monthly tidal variations. In contrast, neap tides, when the sun-earth-moon system forms a right angle, are muted, and in a semi-diurnal tidal system (such as that seen at the CBBT site) this can be seen as a lowest intertidal range.

Two interesting points that arise from comparing these two sites at opposite ends of the Bay are their tidal characteristics - semi-diurnal tide for CBBT and mixed tide for Baltimore (due to resonance in the Bay) - and the differences in amplitude (due to dissipation in the Bay).

Economy

Fishing industry

The Bay is well-known for its seafood, especially blue crabs, clams, and oysters. In the middle of the 20th century, the Bay supported 9,000 full-time watermen, according to one account. Today, the body of water is less productive than it used to be because of runoff from urban areas (mostly on the Western Shore) and farms (especially on the Eastern Shore and in the Susquehanna River watershed), over-harvesting, and invasion of foreign species.

The plentiful oyster harvests led to the development of the skipjack, the state boat of Maryland, which is the only remaining working boat type in the United States still under sail power. Other characteristic bay-area workboats include sail-powered boats such as the log canoe, the pungy, the bugeye, and the motorized Chesapeake Bay deadrise, the state boat of Virginia.

In addition to harvesting wild oysters, oyster farming is a growing industry in the Bay. Oyster aquaculture is passive in that the Bay provides all the natural oyster food needed, making it an environmentally-friendly practice in contrast to other kinds of fish farming. Oyster farms provide jobs as well as a natural effort for filtering excess nutrients from the water in an effort to reduce the effects of eutrophication pollution (too much algae). The Chesapeake Bay Program promotes oyster restoration projects to reduce the amount of nitrogen compounds entering the Chesapeake Bay.

There are numerous ways to cook and eat oysters, as well as recipes and sauces to accompany oyster dishes. One account:

The Bay is famous for its rockfish, a regional name for striped bass. Once on the verge of extinction, rockfish have made a significant comeback because of legislative action that put a moratorium on rockfishing, which allowed the species to re-populate. Rockfish can now be fished in strictly controlled and limited quantities.

Other popular recreational fisheries in the Chesapeake Bay include shad

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