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Generating high quality impervious cover data
S L Bird1, L R Exum, S W Alberty
1US Environmental Protection Agency, Office of Research and Development, National Exposure Research Laboratory, Ecosystems Research Division, Athens, Georgia 30605-2700, USA. bird.sandra@epa.gov
Quality Assurance (San Diego, Calif.)
|January 19, 2002
Summary
Urbanization increases nonpoint source pollution (NPS). This study quantifies impervious cover in Frederick County, Maryland, linking it to stream health and developing estimation methods for better watershed management.
Area of Science:
- Environmental Science
- Hydrology
- Urban Planning
Background:
- Nonpoint source pollution (NPS) is increasing in urban and suburban areas due to population growth.
- A strong correlation exists between impervious cover in drainage basins and receiving stream health.
Purpose of the Study:
- To quantify impervious cover in 56 hydrologic unit codes (HUCs) in Frederick County, Maryland.
- To develop and test methodologies for region-wide impervious cover estimation.
- To provide accurate and reproducible data for watershed management and stream health assessments.
Main Methods:
- Utilized digital orthophoto quarter quadrangles (DOQQ) from the U.S. Geological Survey.
- Employed Geographic Information System (GIS) software for spatial analysis.
- Developed a prototype "cover tool" extension and utilized human analysts for feature identification and categorization.
Main Results:
- Successfully quantified impervious cover across 56 HUCs in Frederick County.
- Developed and validated a system for accurate and reproducible impervious cover estimation.
- Established a dataset to support region-wide impervious cover assessment methodologies.
Conclusions:
- Impervious cover is a critical metric for assessing urban watershed health.
- GIS-based analysis using DOQQ imagery is effective for quantifying impervious surfaces.
- The developed methodologies can be applied to other regions for watershed management and environmental protection.