The free-flowing river meanders for 20 miles before feeding the estuary. It forms much of the border between Prince George's and Charles Counties. It is notable for a broad floodplain and stream valley, much of it forested and a haven for birds, amphibians, and reptiles. These woods are designated an Important Bird Area by the Audubon Society, and according to the U.S. Fish and Wildlife Service are hot spots for biodiversity. Unfortunately, the stream valley, as defined to the top of its slope, is highly threatened by Charles County's land-use plan calling for its development.
Head of tide, a traditional fishing hole maintained by the Masons Springs Conservancy.
Spring Beauties and beaver.
Today, the River Herring run strong in some Mattawoman sites, but usage at other sites upstream has decreased by a factor of 100 in just a decade, as watershed urbanization begins to claim another Chesapeake Bay victim.
American Holly lends greenery in the dead of winter.
The eel pictured to the left might pass another migratory fish, River Herring, that live in the Atlantic Ocean but spawn in fresh water, returning for several years, even in small tributaries like this.
Main stem of the river, being tested for presence of migratory-fish eggs, an annual activity of the Mattawoman Watershed Society each spring.