This layer is one of the South Atlantic LCC indicators in the freshwater aquatic ecosystem. It is an index of impervious surface within each watershed.
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).
National Land Cover Database 2011
(NLCD 2011): Percent developed imperviousness
National Hydrography Dataset Plus Version 2
(NHD Plus Version 2)
1) We calculated percent impervious for each NHD Plus catchment using the NLCD 2011 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 LCC 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 200 m cell size using the ArcGIS Polygon to Raster tool with a cell assignment type of "maximum combined area". The final indicator is continuous, with values ranging as follows:
High: 100% of catchment permeable
Low: 9% of catchment permeable
Defining the Spatial Extent of Ecosystems
Freshwater aquatic indicators were applied to all parts of the South Atlantic LCC geography not classified as marine or estuarine, so no refined extent was needed.
-- May not account for differences in permeability between different types of soils and land uses.
Disclaimer: Comparing with Older Indicator Versions
While this indicator has changed since the
version of permeable surface used in Blueprint 2.0
, this only reflects differences in the way it was calculated and should not be compared to measure change over time.
The South Atlantic ecosystem indicators serve as the South Atlantic LCC's metrics of success and drive the identification of priority areas for shared action in the Conservation Blueprint. To learn more about the indicators and how they are being used, please visit the indicator page. Check out the Blueprint page for more information on the development of the Blueprint, a living spatial plan to conserve our natural and cultural resources.
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.
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.
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. <
Xian, G., Homer, C., Dewitz, J., Fry, J., Hossain, N., and Wickham, J., 2011.
The change of impervious surface area between 2001 and 2006 in the conterminous United States
Photogrammetric Engineering and Remote Sensing
, Vol. 77(8): 758-762.