Citation:

Morgan, J., Y. Wang, AND N. Detenbeck. Mapping Impervious Cover in Catchments Using High Spatial Resolution Aerial Imagery. Edition 2nd edition, Chapter 35, Wang, Yeqiao (ed.), Fresh Water and Watersheds. CRC Press - Taylor & Francis Group, LLC, Boca Raton, FL, , 277-290, (2020). https://doi.org/10.1201/9780429441042

Impact/Purpose:

Under EPA’s Green Infrastructure Initiative, a variety of research activities are underway to evaluate the effectiveness of green infrastructure in mitigating the effects of urbanization and stormwater impacts on stream biota and habitat. Effectiveness of both site-scale stormwater best management practices and landscape-scale natural green infrastructure are being assessed. The percentage of impervious cover in a watershed is a known stressor on stream biota and habitat. Preliminary analyses, using impervious cover estimates from 30-meter resolution National Landcover Dataset (NLCD), have indicated that biotic communities are being impacted at much lower levels of watershed imperviousness than previously reported in the literature. It is likely that the 30-meter resolution NLCD data are underestimating impervious cover, particularly in suburban areas where impervious surfaces can be masked by vegetation and trees. The purpose of this research is to improve EPA assessments of impervious cover by conducting high resolution image analysis using GIS, genetic algorithms, and 1-meter spatial resolution imagery from the National Agriculture Imagery Program (NAIP). The products of the research include the optimization of impervious cover estimates using NAIP data and ancillary data sets such as road networks and E911 data. Post-classification accuracy assessments will compare the improved classifications to previously established impervious cover estimates. These improved estimates will be used to evaluate macroinvertebrate and fish model and threshold accuracy. The results of the project will help to better inform management strategies and regulation of development for suburban and urban areas.

Description:

Understanding how spatial resolution impacts estimates of impervious cover (IC) is important for effective modeling and management of water resources at multiple spatial scales. In this chapter, we introduced an effective methodology for mapping high spatial resolution IC using the National Agriculture Imagery Program (NAIP) imagery. We compared the NAIP-derived high-resolution IC result with the National Land Cover Database (NLCD) impervious cover classifications. This approach provided an improved accuracy in estimation of IC in catchments with different coverage of urban and suburban concentrations. The results demonstrated the need for higher spatial resolution IC data in water quality modeling and in watershed management.

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