Severn Run is the nine-mile-long headwater stream of the Severn River, and is a relatively healthy stream compared to many in the region. With ample shade provided by a largely intact lowland forest of red maple, river birch, sycamore and ash, it is a recreational trout stream, stocked with brook trout by the Department of Natural Resources (DNR). Of the Severn Run's 24 square mile watershed extending from Interstate 97 to Odenton, over 1,700 acres of the Severn Run watershed are protected by Maryland as a preserve designated the Severn Run Natural Environment Area.

Public access is provided at Dicus Mill Road and off Veteran's Highway, but there is little management of this area. Trails along the upper Run are typically overgrown, leaving the floodplain of Severn Run largely in its natural state, with nesting barred owls and great blue herons among other birds.