Evening falls on the Tred Avon River, a tributary in the Choptank River basin, on the eastern shore of the Chesapeake Bay. The Bay and the lower reaches of its tributaries are drowned river valleys. As the ice sheets of the last ice age continue to melt, sea level rises, flooding coastal rivers to create estuaries. Estuaries are essential habitats for both aquatic and land plants and animals. They are also important commercial and recreational resources. Careful resource management of the Bay and the land surrounding tidewater areas are critical to preserve these habitats.
There are many web sites featuring the Chesapeake Bay. Maryland Geological Survey's Coastal Geology Program maintains a site describing MGS's research on the Bay and coast. Other sites include the U.S. Environmental Protection Agency's Chesapeake Bay Program, and the Chesapeake Bay Foundation .