Spring Branch Stream Restoration

Urbanization, flood control, land clearing, and agricultural practices have extensively degraded and disturbed aquatic systems throughout the Northeast. In particular, urban development profoundly impacts the hydrology, morphology, water quality, and biodiversity of streams. Maryland, recognizing the connection between healthy streams and a healthy Chesapeake Bay, developed a comprehensive strategy to restore the tributaries of the Chesapeake Bay watershed. Baltimore County has embarked on one of the most ambitious stream restoration programs to date. The restoration of Spring Branch is a hallmark of their program. Located in the Piedmont Plateau physiographic province, Spring Branch drains approximately 489 acres to the Loch Raven Reservoir, one of several drinking supply reservoirs for the Baltimore metropolitan region. Throughout the last 50 years, the watershed of Spring Branch has undergone intense development. Today, single family homes, on ¼ to ½ acre lots interconnected with curb and gutter roads, blanket the landscape. Impervious surfaces account for more than 50% of the watershed, and, due to the age of the development, stormwater management is absent (typical of northeastern suburban development). On average, 25% of the area contributing stormwater runoff enters the stream via overland flow (non-point source) and 75% via storm drain inputs (point source). The large percentage of drainage area attributable to point sources suggests that the rate of storm runoff entering the stream channel can be described with short, rapid peak hydrographs. These peaks, commonly called "pulse inputs," tend to discharge storm water into the stream channel more quickly and with a greater intensity than streams draining a forested watershed.