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About the Bays


Delaware’s Inland Bays consist of three interconnected bodies of water in southeastern Sussex County: Indian River Bay, Little Assawoman Bay, and Rehoboth Bay.

The Inland Bays are shallow, with an average depth ranging from 3 to 8 feet. Because the bays are so shallow, and because they are poorly flushed by tidal movement, they are especially sensitive to environmental changes. Increases in pollutants, changes in salinity and fluctuations in water temperature, for example, can have dramatic effects on water quality and on the plants, fish, shellfish, and microscopic creatures that live in the bays.


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The Inland Bays Watershed

The bays and their tributaries cover about 32 square miles and drain a land mass -called a “watershed”- of about 320 square miles.  

The watershed itself reaches to the north to the southern edge of the Delaware Bay in Lewes. From there, it extends south through Rehoboth Beach, Dewey Beach, Bethany Beach and South Bethany to its southern border in Fenwick Island at the Maryland State Line.

Heading west, the Inland Bays watershed weaves through the eastern portion of Sussex County, enveloping the towns nearest Rt 113 including Selbyville, Frankford, Dagsboro, Millsboro and Georgetown, and ending just before reaching Rt. 404.


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Issues Affecting the Bays

Two major areas of concern have been identified as critical issues for Delaware’s Inland Bays— eutrophication (rapid plant growth due to excessive nutrients) and habitat loss.

Due to urbanization, agricultural activities, and low flushing rates, the Bays have become highly enriched with nitrogen and phosphorus. While these nutrients are essential for plant and animals growth , when present in excessive amounts, water quality can deteriorate as aquatic plant growth accelerates and the level of oxygen is reduced. In December 1998, the Delaware Department of Natural Resources and Environmental Control promulgated Total Maximum Daily Loads (TMDLs) for nitrogen and phosphorus for the Indian River, Indian River Bay, and Rehoboth Bay. A TMDL was promulgated for the Little Assawoman Bay in December 2004. To meet the load reductions required by the TMDLs, water quality goals include the elimination of all point sources if nutrient loading to the water bodies, along with a 40% reduction in nonpoint phosphorus loading in the Indian River Bay., Rehoboth Bay and Little Assawoman Bay, 1 65% reduction in the upper Indian Rover Watershed, a 40% reduction of nonpoint nitrogen loading in the Indian River Bay, Rehoboth Bay and Little Assawoman Bay, and an 85% reduction in the upper Indian River Watershed.

The concern of nutrient over-enrichment points to the need to reduce nutrient contributions from a variety of point and non-point sources in the watershed. 

In addition to these problems, the loss of valuable aquatic, upland, and wetland habitat stresses conditions of the Inland Bays.


Further Reading…

These books have been hand-selected to help you learn more about our Inland Bays Watershed. Anything marked with an asterisk is*Great to read to children, yet informative for adults.

  • Between the Ocean and Bay: A Natural History of Delmarva, Jane Scott
  • A Place Between the Tides: A Naturalist’s Reflections on the Salt Marsh, Harry Thurston
  • Between Ocean and Bay: A Celebration of the Eastern Shore, Jim Clark
  • Teaching the Trees: Lessons from the Forest, Joan Maloof
  • Delaware Trees, William S. Taber
  • Common Plants of the Mid-Atlantic Coast:  A Field Guide, Gene M. Silberhorn 
  • Horseshoe Crab Biography of a Survivor, Anthony D. Fredericks
  • *Horseshoe Crabs and Shorebirds:  The Story of a Foodweb, Victoria Cresson and Annie Cannon
  • *Crab Moon, Ruth Horwitz
  • Birds of Delaware (Pitt Series in Nature and Natural History), Gene Hess and Richard West
  • *Red Knot: A Shorebird’s Incredible Journey, Nancy Carol Wilis
  • The Flight of the Red Knot: A Natural History Account of a Small Bird’s Annual Migration from the Artic Circle to the Tip of South America and Back, Brian Harrington
  • The Narrow Edge: A Tiny Bird, an Ancient Crab, and an Epic Journey, Deborah Cramer
  • Salt Marshes: A Natural and Unnatural History, Judith S. Weis and Carol A. Butler
  • *A Journey into an Estuary, Rebecca L. Johnson