Physiographic Province Map of Maryland, Delaware, and the District of Columbia
Definitions of Physiographic Provinces (From West to East):
Appalachian Plateau - The Appalachian Plateau is a region of flat-lying to gently folded rocks. The high relief in the area (often exceeding 500 ft) is due to erosion by streams and rivers. Aquifer material is composed of fractured sedimentary rocks. Water yielding rocks are typically sandstones and, occasionally, coal seams.
Valley and Ridge / Blue Ridge - The Valley and Ridge and Blue Ridge region has relief commonly in excess of 500 ft. The area is underlain by metamorphic, igneous, sedimentary, and carbonate rocks. Aquifers in the region consist of fractured metamorphic, igneous, and sedimentary rocks. Regolith is typically thinner than in the Piedmont and faulting and folding typically greater.
Piedmont - The Piedmont has considerably more topographic relief than the Coastal Plain with gently rolling uplands having as much as 500 ft. of local relief. The region is underlain by metamorphic and igneous rocks with an overburden of unconsolidated material known as regolith. The water-table aquifer is in the regolith and extends to the underlying bedrock. Aquifers below the water table are related to a complex pattern of joints, fractures, fault zones, and cleavage planes.
Coastal Plain - The Coastal Plain is characterized by gently rolling hills and valleys. It is underlain by a southeastwardly thickening sequence of sediments that consists of sand and gravel aquifers interlayered with silt and clay confining units.