Section 3. Managing Watershed Stresses
IMPERVIOUS
SURFACES AND URBAN STORM WATER
Impervious cover and storm water runoff from roof tops, roads and parking
areas are two of the largest stresses on the watershed. They are difficult
to manage because they can occur nearly anywhere as “non-point”
sources. These stresses will steadily increase unless aggressive actions are
taken to deal with them.
The basic problem
is that inadequately planned land development significantly reduces groundwater
recharge, increases rates and volumes of runoff to surface waters, and adds
urban pollutants into the aquatic ecosystem. Affected streams are subject
to more frequent and higher intensities of storm flooding and corresponding
reduced flows during periods of lower precipitation. In turn, these altered
conditions lead to fundamental changes in aquatic habitats.
Approximately one-third of the impaired streams in the watershed are impacted
by urban runoff. Most of these are associated with highly developed areas
in the watershed, such as Wissahickon Creek.
Pennsylvania’s Storm Water Management Act (Act 167) provides funding for counties to prepare watershed plans to manage storm water runoff. These plans are implemented by municipalities through local ordinances. As of 2000, approximately 45 of the watershed’s 238 municipalities (19 percent) have such plans completed or underway.
Figure 31.
Streams Impaired by Development and
Urban
Storm Water Pennsylvania Department
of Environmental Protection (305b Report), 2000
Site Design: Tevlin & Clarke
