The principal objective of this project is to document the effects of
urbanization on Valley Creek Watershed, which lies in a rapidly
developing area of suburban Philadelphia, Pennsylvania. Valley Creek
is a tributary of the Schuylkill River and runs through Valley Forge
National Historical Park. The watershed lies in the Piedmont
physiographic province, and supports a reproducing brown trout
population in its limestone-fed stream. In addition to the common
effects of development such as increased surface runoff and sediment
loading, the watershed has experienced point-source pollution
problems from RCRA and CERCLA hazardous waste sites and dewatering of
the aquifer due to quarrying operations and pumping for municipal
water supply.
We are conducting a historical review of land use in an attempt to
quantify the changes in the stream caused by development over the
last 200 years. Specifically, we are looking at changes in
population, building permits, road mileage, and land use patterns
from colonial times to present. Once we have established the effects
of prior development in the watershed, we will assess the effect of
the continuing urbanization of the area. Because the watershed is
actively undergoing urbanization, we will attempt to directly examine
the development-induced geomorphologic changes in the stream over
time. The primary conditions we are observing are: stream flows (base
and storm flows), channel morphology, bed composition, and suspended
sediment concentrations.
We are quantifying the degree and pattern of heterogeneity of
hydraulic conductivity of this fractured rock aquifer at multiple
scales from existing hydrogeologic data. We are evaluating the effect
of aquifer heterogeneity and three-dimensional flow pathways on
stream-subsurface exchange rates and contaminant transport using
groundwater flow and transport models. This information will in turn
be used to assess the chemical loadings to the fish and other biota
in the stream. Stream tracer-injection experiments are being used to
directly assess stream-subsurface exchange in Valley Creek and
storage of tracer in the hyporheic zone.
We are investigating several aspects of the interaction between
environmental quality and the biota in this watershed. First, we are
collecting sediment distribution data to assess impacts of changes in
channel characteristics on community structure of macroinvertebrates
and fish. Second, we are comparing sediment PCB levels and supply
rates with PCB levels in the organisms from the same areas. Third, we
are assessing positioning of species in the food web in order to
measure biomagnification via food web processes. Fourth, we are
measuring general stress levels in the organisms and relating this to
PCB levels as an independent indicator of environmental impacts on
organisms. This analysis will allow us to develop a comprehensive
picture of how urbanization-induced changes in the watershed affect
invertebrate and fish communities.
Political controversies in this watershed have left a documented
historical record of the political struggles that develop in the
process of urbanization. We are identifying the major development
activities that have had an impact on the watershed over time and we
will next examine the political decision making associated with these
activities. By examining these political decisions, an understanding
of the political forces involved in urbanization can be developed.
The social science research is based on the use of three
social-science perspectives: (1) the Advocacy Coalition Framework,
(2) network analysis, and (3) discourse analysis. These sociological
perspectives define an image of watershed politics as being the
result of the formation of different advocacy coalitions, each with a
specific network structure and unique belief system. What will emerge
from this research is a comprehensive historical view of the process
of urbanization, including the influence of social, economic, and
political factors.