This indicator is a continuous index that measures the amount of natural landcover in the estimated floodplain, by catchment.
Reason for Selection
Habitat near rivers and streams is strongly linked to water quality and instream flow (Naiman 1997), is easy to monitor and model, and is widely used and understood by diverse partners. These buffers provide a “front line defense” for aquatic systems.
– 2016 National Land Cover Database (NLCD)
– National Hydrography Dataset Plus Version 2 (NHD Plus Version 2)
1) We used the EPA estimated floodplain layer to estimate riparian buffers.
2) We mapped natural landcover using the following National Land Cover Data 2016 classes: open water, barren land, deciduous forest, evergreen forest, mixed forest, scrub/shrub, grassland/herbaceous, woody wetlands, and emergent wetlands.
3) We intersected the two layers listed above (EPA estimated floodplain layer and natural landcover) to capture the natural landcover classes that fell within the estimated floodplain.
4) We calculated the percent of riparian natural landcover inside each NHD Plus Version 2 catchment using the ArcGIS Zonal Statistics tool.
5) We took the resulting raster times 100 and converted it to an integer, so that the percentages are shown in whole numbers.
Final indicator values
The final indicator is continuous, with values ranging as follows:
High: 100% natural habitat within the estimated floodplain, by catchment
Low: 0% natural habitat within the estimated floodplain, by catchment
The EPA Estimated Floodplain Map of the Conterminous U.S. displays “…areas estimated to be inundated by a 100-year flood, also known as the 1% annual chance flood. These data are based on the Federal Emergency Management Agency (FEMA) 100-year flood inundation maps with the goal of creating a seamless floodplain map at 30-meter resolution for the conterminous United States. This map identifies a given pixel’s membership in the 100-year floodplain and completes areas that FEMA has not yet mapped.”
– Does not account for accumulated impacts of upstream riparian buffers. Buffers at the headwaters are treated the same as those downstream.
– Does not account for variation in buffer quality within the floodplain at a scale below the catchment. This means that within the estimated floodplain, loss of natural habitat adjacent to the river is treated the same as loss farther away.
–While this indicator generally includes the open water area of reservoirs, some open water portions of Kerr Lake are missing from the estimated floodplain dataset.
–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 email@example.com).
EPA EnviroAtlas. 2018. Estimated Floodplain Map of the Conterminous U.S.https://enviroatlas.epa.gov/enviroatlas/DataFactSheets/pdf/Supplemental/EstimatedFloodplains.pdf
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.
Martin, E. H, Hoenke, K., Granstaff, E., Barnett, A., Kauffman, J., Robinson, S. and Apse, C.D. 2014. SEACAP: Southeast Aquatic Connectivity Assessment Project: Assessing the ecological impact of dams on Southeastern rivers. The Nature Conservancy, Eastern Division Conservation Science , Southeast Aquatic Resources Partnership. http://data.southatlanticlcc.org/SEACAP_Report.pdf.
Naiman, Robert J., and Henri Decamps. “The Ecology of Interfaces: Riparian Zones.” Annual Review of Ecology and Systematics 28 (1997): 621–58.
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/.
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