This indicator is a continuous index that measures the percent of non-impervious cover by catchment.
Reason for Selection
Impervious cover is easy to monitor and model, and is widely used and understood by diverse partners. It is also strongly linked to water quality, estuary condition, eutrophication, and freshwater inflow (Schueler et al. 2009, Wenger et al. 2008, Uphoff et al. 2011).
Input Data
– 2016 National Land Cover Database: Percent developed imperviousness
– National Hydrography Dataset Plus Version 2 (NHD Plus Version 2)
Mapping Steps
1) We calculated percent impervious for each NHD Plus catchment using the NLCD 2016 impervious surface layer and the ArcGIS Zonal Statistics as Table tool.
2) We converted percent impervious to percent permeable using the formula [percent permeable = 100 - percent impervious] to maintain consistent scoring across South Atlantic indicators (high values indicate better ecological condition) and joined the resulting table back to NHD Plus catchment layer.
3) We converted vector catchments to a raster with 30 m cell size using the ArcGIS Polygon to Raster tool with a cell assignment type of maximum combined area.
Final indicator values
High: 100% of catchment permeable
Low: 9% of catchment permeable
Known Issues
– May not account for differences in permeability between different types of soils and land uses.
–The catchment boundaries are inconsistent in how far they extend toward the ocean. As a result, this indicator does not consistently apply to estuaries, coastal areas, and barrier islands in different parts of the South Atlantic.
**Disclaimer: Comparing with Older Indicator Versions **
There are numerous problems with using South Atlantic indicators for change analysis. Please consult Blueprint staff if you would like to do this (email hilary_morris@fws.gov).
Literature Cited
Homer, Collin G., Dewitz, Jon A., Jin, Suming, Xian, George, Costello, C., Danielson, Patrick, Gass, L., Funk, M., Wickham, J., Stehman, S., Auch, Roger F., Riitters, K. H., Conterminous United States land cover change patterns 2001–2016 from the 2016 National Land Cover Database: ISPRS Journal of Photogrammetry and Remote Sensing, v. 162, p. 184–199, at https://doi.org/10.1016/j.isprsjprs.2020.02.019.
James H. Uphoff Jr., Margaret McGinty, Rudolph Lukacovic, James Mowrer & Bruce Pyle (2011): Impervious Surface, Summer Dissolved Oxygen, and Fish Distribution in Chesapeake Bay Subestuaries: Linking Watershed Development, Habitat Conditions, and Fisheries Management, North American Journal of Fisheries Management, 31:3, 554-566.
Schueler, T., Fraley-McNeal, L., and Cappiella, K. (2009). ”Is Impervious Cover Still Important? Review of Recent Research.” J. Hydrol. Eng. 14, SPECIAL ISSUE: Impervious Surfaces in Hydrologic Modeling and Monitoring, 309–315.
Wenger, S. J., J. T. Peterson, M. C. Freeman, B. J. Freeman, D. D. Homans. 2008. Stream fish occurrence in response to impervious cover, historic land use and hydrogeomorphic factors Canadian Journal of Fisheries and Aquatic Sciences 65, 1250-1264.
U.S. Environmental Protection Agency (USEPA) and the U.S. Geological Survey (USGS). 2012. National Hydrography Dataset Plus. 2.10. http://www.horizon-systems.com/nhdplus/.
