Imperiled Aquatic Species

This indicator measures the number of aquatic animal Species of Greatest Conservation Need (SGCN) observed within each 12-digit HUC subwatershed, including fish, mussels, snails, crayfish, and amphibians. SGCN are identified in State Wildlife Action Plans as most in need of conservation action. This indicator originates from state Natural Heritage Program data collected by the Southeast Aquatic Resources Partnership and applies to the Environmental Protection Agency’s estimated floodplain, which spatially defines areas estimated to be inundated by a 100-year flood, also known as the 1% annual chance flood.

Reason for Selection

This indicator identifies areas with abundant rare and endemic aquatic species that would benefit from conservation action. It captures patterns of rare and endemic species diversity not well-represented by other freshwater indicators.

Input Data

• Base Blueprint 2022 extent

• Southeast Aquatic Resources Partnership (SARP) SGCN HUC12 summaries

  The Southeast Aquatic Resources Partnership provided these summaries in January 2022 as a geodatabase containing one polygon feature class of HUC12 watersheds and an attribute for the number of aquatic animal SGCNs observed in that watershed. This dataset is based on state Natural Heritage Program occurrence records for fishes, mussels, snails, crayfish, and amphibians. It was last updated in January 2022. More information on this dataset is available in Appendix A of the Southeast Blueprint 2022 Development Process.

• Estimated Floodplain Map of the Conterminous U.S. from the EPA EnviroAtlas (see this factsheet for more information; download the data)

  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-m 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” (EPA 2018).

• National Hydrography Dataset Plus (NHDPlus) Version 2.1 medium resolution catchments (note: V2.1 is just the current sub-version of the dataset generally called NHDPlusV2 - view the user guide for more information)

  NHDPlus V2.1 Medium Resolution Catchments

  A catchment is the local drainage area of a specific stream segment based on the surrounding elevation. Catchments are defined based on surface water features, watershed boundaries, and elevation data. It can be difficult to conceptualize the size of a catchment because they vary significantly in size based on the length of a particular stream segment and its surrounding topography—as well as the level of detail used to map those characteristics.

  More specifically, the NHDPlus V2.1 medium resolution catchment dataset used in this indicator incorporates snapshots of a) surface water features from the medium-resolution (1:100K scale) National Hydrography Dataset b) watershed boundaries from the Watershed Boundary Dataset, and c) the National Elevation Dataset 30 m digital elevation model.

  To learn more about catchments and how they’re defined, check out these resources:

  • Basic information on NHDPlus from the EPA
  • An article from USGS explaining the differences between various NHD products
  • The NHDPlus V2.1 User Guide, which explains in detail how the dataset was produced
  • The glossary at the bottom of this tutorial for an EPA water resources viewer, which defines some key terms
  • Esri USA States Generalized

Mapping Steps

• Reclassify the SGCN count attribute field from the SARP SGCN dataset into the indicator values below.
• Convert the SARP SGCN HUC12 dataset to a 30 m raster, using the indicator values attribute made in the previous step.
• Mask the resulting raster to the EPA estimated floodplain.
• Mask the resulting floodplain-masked raster to the NHDPlus catchments layer to remove values in the nearshore environment.
• Mask to the spatial extent of Base Blueprint 2022 excluding the state of West Virginia, using the Esri USA states layer to provide the West Virginia state boundary.

Note: For more details on the mapping steps, code used to create this layer is available in the Southeast Blueprint 2022 Data Download under BlueprintInputs > BaseBlueprint2022 > 6_Code.

Final Indicator Values

Indicator values are assigned as follows:

• 8 = 8+ aquatic Species of Greatest Conservation Need (SGCN) observed
• 7 = 7 aquatic SGCN observed
• 6 = 6 aquatic SGCN observed
• 5 = 5 aquatic SGCN observed
• 4 = 4 aquatic SGCN observed
• 3 = 3 aquatic SGCN observed
• 2 = 2 aquatic SGCN observed
• 1 = 1 aquatic SGCN observed
• 0 = No aquatic SGCN observed

Known Issues

• As this indicator is based on occurrence records, poorly surveyed areas may be scored too low. Therefore, this data does not imply absence of species.
• While this indicator generally includes the open water area of reservoirs, some open water portions of reservoirs (e.g., Kerr Lake in NC/VA) are missing from the estimated floodplain dataset.
• Small headwaters and creeks are not included in this indicator because the EPA estimated floodplain dataset does not include them.
• As most Southeast states do not identify plants as SGCNs, this layer includes aquatic animal species only.
• This indicator draws from data provided by SARP, which does not cover the full state of West Virginia. To fill that gap, we developed the West Virginia imperiled aquatic species indicator using a different data source. While states that neighbor West Virginia (Kentucky and Virginia) submitted species observations to SARP for HUC12s that cross over into West Virginia, we erased the values within West Virginia since we lacked complete information for those HUCs and the West Virginia imperiled aquatic species indicator already covered those areas in a more consistent way. In future Blueprint updates, we are working to expand the full imperiled aquatic species indicator to West Virginia to avoid the need for a separate indicator.
• In the area just south of Guadalupe Mountains National Park in West Texas, this indicator depicts the floodplain as a series of linear lines that poorly match the actual floodplain. This is due to an error in the EPA floodplain map used in this indicator.

Disclaimer: Comparing with Older Indicator Versions

There are numerous problems with using Southeast Blueprint indicators for change analysis. Please consult Blueprint staff if you would like to do this (email hilary_morris@fws.gov).

Literature Cited

EPA EnviroAtlas. 2018. Estimated Floodplain Map of the Conterminous U.S. [https://enviroatlas.epa.gov/enviroatlas/DataFactSheets/pdf/Supplemental/EstimatedFloodplains.pdf].

Esri. U.S. States (Generalized). Published 2017-12-21. Data and Maps for ArcGIS®. 2017 - World, Europe, and United States. Redlands, California, USA [https://www.arcgis.com/home/item.html?id=99fd67933e754a1181cc755146be21ca].

Southeast Aquatic Resources Partnership. Species Summaries by HUC12. Accessed January 2022.

U.S. Environmental Protection Agency (USEPA) and the U.S. Geological Survey (USGS). 2012. National Hydrography Dataset Plus 2. [http://www.horizon-systems.com/nhdplus/].