Description: Hydrologic unit boundaries define the aerial extent of surface water drainage to a point. Hydrologic units through four levels were created in the 1970's and have been used extensively throughout the United States. During that time the U.S. Geological Survey (USGS) developed a hierarchical hydrologic unit code (HUC) for Hydrologic unit boundaries define the aerial extent of surface water drainage to a point. Hydrologic units through four levels were created in the 1970's and have been used extensively throughout the United States. During that time the U.S. Geological Survey (USGS) developed a hierarchical hydrologic unit code (HUC) for the United States. This system divides the country into 21 Regions, 222 Subregions, 352 Accounting Units, and 2,149 Cataloging Units based on surface hydrologic features. The smallest USGS unit (8-digit HU) is approximately 448,000 acres. During the late 1970's the Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service, initiated a national program to further subdivide HU's into smaller watersheds for water resources planning. A 3-digit extension was added to the 8-digit identification. By the early 1980's this 11-digit HU mapping was completed for most of the U.S. These data demonstrate Maryland's watersheds as represented by the federal Hydrologic Unit Code denoted by an 11-digit numerical code. The watersheds were defined using contours on U.S. Geological Survey (USGS) 7.5 minute quadrangle map sheets. The state has been divided into 138 watersheds that are identified by Maryland, using an 8-digit numerical code. These watersheds are equivalent to the HUC 11-digit codes. The watershed file is generally considered to be map accurate at a scale of 1:24,000. A new 12-digit watershed file is available from DNR which provides more detailed line work for over 1,100 watersheds which is approximately equivalent to the HUC 14-digit code.
Description: This file (SWSUB8) is a statewide digital watershed file. It depicts the State with 138 separate watersheds each with an 8-digit numeric code. The file was created primarily for State and Federal agency use. The creation of this file goes back many years and involved several State and Federal agencies. This file was derived from a more detailed watershed file (Maryland's Third-Order Watershed). The process used to create this file is consistent with the elevation contour information found on the US Geological Survey's 7.5 minute topographic quadrangle maps and the Maryland Department of the Environment's watershed location and naming conventions. This file is similar, but not identical, to the US Natural Resources Conservation Service's (NRCS) Hydrologic Unit Code (HUC11) watershed file. The watersheds define Strahler (Strahler 1952 p.1120) third order stream drainage by contours on U.S. Geological Survey (USGS) 7.5 minute quadrangle map sheets. Some watershed drainage areas were defined for streams less than third order and some large area Watersheds were split to maintain a maximum size of 15,000 acres.
Description: This file (SWSHED12) is a statewide digital watershed file. It was created primarily for state and federal agency use. The watersheds define Strahler (Strahler 1952 p. 1120) third order stream drainage by contours on U.S. Geological Survey (USGS) 7.5 minute quadrangle map sheets. Some watersheds drainage areas were defined for streams less than third order and some large area watershed were split to maintain a maximum size of 15,000 acres. The watershed boundaries in this file were developed in a joint state and federal effort to create a consistent watershed file for use by all government agencies with an interest in Maryland's watersheds. The U.S. Natural Resources Conservation Service (NRCS) redefined the third order watersheds creating the HUA14 file. This file contains all of the HUA14 watersheds and some added watersheds to maintain water quality sampling sites. It was also used to create the Maryland Sub-Watershed file.
Description: The Maryland coastal zone is comprised of the land, water and subaqueous land between the territorial limits of Maryland in the Chesapeake Bay, Atlantic Coastal Bays and the Atlantic Ocean, as well as the towns, cities and counties that contain and help govern the thousands of miles of Maryland shoreline. The Maryland coastal zone extends from three miles out in the Atlantic Ocean to the inland boundaries of the 16 counties and Baltimore City that border the Atlantic Ocean, Chesapeake Bay and the Potomac River up to the District of Columbia. This area encompasses two-thirds of the State’s land area and is home to almost 70% of Maryland’s residents.
Description: Maryland Tributary Teams-comprised of local citizens, farmers, business leaders and government officials appointed by the Governor-are working to keep local waterways clean and healthy. TheTributary Team jurisdictions were determined from the watershed boundaries that were developed in a joint state and federal effort to create a consistent watershed file for use by all government agencies with an interest in Maryland's watersheds.