Impervious Surface Trend

Percent Impervious Cover
These layers give more information about the impervious cover indicator for the South Atlantic LCC.  These layers show the change in percent impervious cover over time and the projected change in the future. To read more about the indicators and how they are being used, please visit the  indicator page.

Reason for selection:
Impervious cover is easy to monitor and model, widely used and understood by diverse partners, and is strongly linked to water quality, estuary condition, eutrophication, and freshwater inflow
Target:
Maintain percent of catchments that have 10% or less impervious cover

Input Data:

• NHDPlus smoothed catchments (Version 01_01)
• Attributes for NHDPlus Catchments (Version 01_01) for the Conterminous United States: NLCD 2001 Impervious
• NLCD 2006 Impervious 5/4/2011
• NLCD 2011 Impervious 03/31/2014
• ICLUS version 1.3 Percent Impervious Surface Projections, A2, 2050

Mapping Steps:

1. For 2001, 2006 and 2011, mean percent impervious (from NLCD) for each NHDPlus in the SALCC + ACF basin was calculated using ArcGIS zonal statistics as table
2. For 2050, first the ICLUS version 1.3 Percent Impervious Surface Projection, A2, 2050 was resampled to a 30x30 meter pixel (so that the zonal statistics would work using the very small catchments as the zone data).  Then mean percent impervious (from the resampled ICLUS A2 2050) for each NHDPlus Catchment was calculated using ArcGIS zonal statistics as table
3. For each year calculate the total number of catchments that have greater than 10% mean impervious cover

Known Issues:

• Differences between methods of calculating/projecting impervious surfaces can make it difficult to compare across years