Rivers and Streams

Water is the life-line of C&O Canal NHP. Adjacent to the Potomac River for 184.5 miles from the District of Columbia to Cumberland, Maryland, there are 261 perennial streams; 4 water bodies (Little Pool, Big Pool, Seneca Swamp, Widewater); estimated 54.4 miles of watered canal (35.9 miles maintained watered canal, 7.7 miles year-round naturally watered canal, 10.8 ephemerally watered canal); 27 documented springs/seeps; and an unknown number of other wetlands. Flooding is a natural process that has shaped and reshaped the Potomac River Valley for a long time. Ground was broken for the C&O Canal in 1828. The following year, the canal experienced its first flood. By 1996, 17 major floods and numerous minor ones have impacted life of the canal. These floods have caused millions of dollars in damages to historic structures along the canal, and a major flood in 1924 ultimately caused the Canal Company to cease operation. The potentially devastating force of flooding is also largely responsible for the extraordinary biological diversity of the park. Flooding has been a part of the Potomac River for millions of years. As a result, flood-adapted habitats such as floodplain forests and scourbars, have been created. These habitats have gained significance in Maryland and nationally due to increasing habitat loss and fragmentation from development and invasion of exotic plant species. In fact, many rare plants depend on these unique habitats created by the river. Like so many things in nature, floods occur in cycles that fluctuate in frequency and magnitude. Floods also occur at different times of the year. Many Potomac River floods occur in spring after heavy rainfall when the ground may still be frozen, preventing runoff from being absorbed. Periodic inundation of the banks of the Potomac River and bordering C&O Canal NHP benefits the natural system as a whole. Silt, enriched by nutrients and minerals, is deposited by flood waters creating fertile soils which foster biological diversity. Many spring wildflowers thrive in floodplain habitat, which comprises about 85% of the park.