This photography was flown in order to have recent photo coverage, at a reasonably large scale, of
the tributary watersheds around the Delaware Water Gap. The imagery was photointerpreted for landuse
and landcover and is being used for a study on forest fragmentation and its effects on water quality.
The primary reason for choosing this particular area was the need for the Delaware Water Gap National
Recreation Area (NRA), managed by the National Park Service (NPS), to monitor and try to maintain the
quality of the stream water entering the park. The USGS National Water Quality Assessment (NAWQA)
program and the USGS Water Resources Division (WRD) will be collecting stream sample data in the
summers of 2001 and 2002. The landuse and landcover information derived from this photography will
be summarized, and measures of how the forest and developed landuses are distributed in the basins
with respect to the streams and sample sites will be calculated. The relationship between these
different parameters of fragmentation and current water quality will be analyzed. The data will also
provide baseline information for monitoring these watersheds over time.
The photography was considered necessary because the satellite-derived landuse/landcover maps in the
area (e.g. NLCD’92 and PA GAP) were not picking up the numerous residential areas in this region.
This gap is understandable, because of the large amounts of tree cover in these residential areas,
however the project needed to have more accurate information for investigating how these parameters
of fragmentation and landuse composition were related to changes in water quality. The imagery was
thus acquired to get an accurate picture of the current status of forest fragmentation and landuse
composition in the area.
In addition to the work on forest fragmentation and water quality, the data will also be used as a
source of comparative truth about actual land use to try to improve the accuracy of TM-derived
datasets in this regard. Detailed mapped photointerpretation as was used in this project is
expensive and thus not suited to mapping over large areas. Thus, if we can utilize TM-derived data
sources, and other existing information on potential human impact such as road densities or housing
densities, to derive the relevant parameters of forest fragmentation and land use context, we will be
able to map the status of forest fragmentation and land use context over larger areas. Before we can
do so at the scales that are often relevant to changes in water quality, forest composition and
health, and some habitats, we need to find ways to improve the ‘fragmentation accuracy’ of the land
use datasets we are working with.
This study is being expanded this summer (2002) to include many of the basins sampled by USGS NAWQA
program as part of their larger effort to study the effects of urbanization on streams in the
Piedmont and Appalachaian ecoregions of the Delaware River Basin. From this broader gradient of
conditions, we hope to address questions like: Which aspects of urbanization and forest
fragmentation cause ecological responses? And which of these are ‘manageable’? And is the effect
gradual or is there a threshold beyond which change is substantial? Those parameters of urbanization
and forest fragmentation that are most strongly correlated to change will be those we are interested
in monitoring most accurately over the entire region over time. This effort will utilize the 1999
DOQQs now available, but will use most of the same landuse/landcover classes. This photointerpreted
data will also be made available on this site when it is completed, probably by the end of 2002.
This project is part of a larger Collaborative Environmental Monitoring and Research Initiative
(CEMRI) between the US Geological Survey (USGS), US Forest Service (USFS), the National Park Service
(NPS), and other agencies to implement a prototype environmental monitoring strategy that will link
air quality, hydrological and forestry information across the landscape of the Delaware River Basin.
(for more info, see the CEMRI web site at: http://www.fs.fed.us/ne/global/research/drb/).