Indicator V 2.1: Freshwater Aquatic - Riparian Buffers

Nov 9, 2015 (Last modified Sep 6, 2016)
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Description:
Riparian Buffers 
This layer is one of the South Atlantic LCC indicators in the freshwater aquatic ecosystem. It is a riparian buffer index capturing natural habitat near rivers and streams.
  
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. 

Input Data 
-- Southeast Aquatic Connectivity Assessment Project (SEACAP)
-- National Land Cover Database 2011 (NLCD 2011)
-- National Hydrography Dataset Plus Version 2 (NHD Plus Version 2)

Mapping Steps 
1) We mapped riparian buffers using the SEACAP Active River Area layer.
2) Natural landcover was mapped using the following National Land Cover Data 2011 classes: open water, barren land, deciduous forest, evergreen forest, mixed forest, scrub/shrub, grassland/herbaceous, woody wetlands, and emergent wetlands.  
3) The two layers listed above (riparian buffers and natural landcover) were intersected to capture the natural landcover classes that fell within the Active River Area. 
4) We calculated the percent of riparian natural landcover inside each NHD Plus Version 2 catchment using the ArcGIS Zonal Statistics as Table tool and joined the resulting table back to the NHD Plus catchment layer. 
5) We converted the percent riparian natural landcover by catchment vector layer to a raster with 200 meter 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% natural habitat surrounding rivers and streams by catchment
Low: 0% natural habitat surrounding rivers and streams by catchment

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.

Definitions
Active River Area:
SEACAP developed an Active River Area layer (final SEACAP report, page 21):

"The Active River Area (ARA) is a 'spatially explicit framework for modeling rivers and their dynamic interaction with the land through which they flow' (Smith et al. 2008). Key features of the ARA include the meander belt, riparian wetlands, floodplains, terraces, material contribution areas. The ARA is different from, but was calibrated to and compared against, the FEMA 100‐year floodplain. SEACAP used the ARA as a unit within which various landcover metrics, such as forest cover and impervious surface, were summarized. For the SEACAP area, we delineated the ARA for each of the seven size classes described in Section 2.1.3, using a seamless mosaic of 10m DEM data from the National Elevation Dataset (Gesch 2007; Gesch et al. 2002) as well as stream polylines, waterbody polygons, and stream area polygons from the NHDPlus v2 dataset. We selected and resampled wetflat landforms from a 30m landform model developed for the Southeastern United States (Anderson et al. 2014) to identify ARA components that occurred on wetflats and where longer-term storage of water is expected to occur. In addition, we obtained 100-yr floodplain polygons from the FEMA National Flood Hazard Layer (NFHL) in spring 2013 and used this data to inform cost distance threshold selection in the ARA delineation. Any FEMA 100-yr floodplain areas that were not captured by the ARA delineation were gridded at 10m resolution and merged underneath the ARA components in the final product. The final 10m ARA was resampled to 30m for use in the SEACAP metric calculations due to the resolution of other key input datasets (i.e., landcover). 22 The methods used to calculate all metrics was automated and documented via ArcGIS Model Builder models and custom Python scripts. Contact the authors for more information on the methods used to calculate metrics."

Known Issues
-- 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 Active River Area at a scale below the catchment. This means that within the Active River Area, loss of natural habitat adjacent to the river is treated the same as loss farther away.

Disclaimer: Comparing with Older Indicator Versions
While this indicator has changed since the version of riparian buffers 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.

Indicator Overview
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.

Literature Cited
Homer, C.G., Dewitz, J.A., Yang, L., Jin, S., Danielson, P., Xian, G., Coulston, J., Herold, N.D., Wickham, J.D., and Megown, K., 2015, Completion of the 2011 National Land Cover Database for the conterminous United States-Representing a decade of land cover change informationPhotogrammetric Engineering and Remote Sensing, v. 81, no. 5, p. 345-354.

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. <maps.tnc.org/seacap>

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/>

Data Provided By:
South Atlantic LCC
Data Hosted by:
ScienceBase (USGS) View Record
Map Service URL:
https://www.sciencebase.gov/arcgis/rest/services/Catalog/56402cf2e4b0831b7d62e40c/MapServer/
Content date:
2016-05-06 (Release Date)
Contact Organization:
South Atlantic Landscape Conservation Cooperative
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Use Constraints:

This work is licensed under a Creative Commons Attribution 4.0 International License. The indicator data and maps provided are only intended for use as a reference tool for landscape-level conservation planning efforts.
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SouthAtlantic LCC
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The South Atlantic LCC encompasses and ecologically diverse 89 million acres across portions of six states, from southern Virginia to northern Florida. The geography also includes the marine environment within the federal Exclusive Economic Zone The South Atlantic region is a place where major...