{2419b680-9fec-4c8c-8516-302206d3be4c} eng; USA utf8 dataset EnviroAtlas Coordinator U.S. Environmental Protection Agency, Office of Research and Development-Sustainable and Healthy Communities Research Program, EnviroAtlas Geospatial Data Owner (919) 541-3832 109 T.W. Alexander Drive Research Triangle Park NC 27709 EnviroAtlas@epa.gov https://www.epa.gov/enviroatlas pointOfContact 2025-07-23 ISO 19115 Geographic Information - Metadata ISO 19115:2003/Cor.1:2006(E) EnviroAtlas - Dasymetric Population by 12-Digit HUC for the Conterminous United States 2018-01-24 publication U.S. EPA Office of Research & Development (ORD) - National Exposure Research Laboratory (NERL) Research Triangle Park NC publisher US Environmental Protection Agency (US EPA) originator This EnviroAtlas dataset estimates population by 12-digit HUC. It is based on the EnviroAtlas dasymetric dataset, which intelligently reallocates 2010 population from census blocks to 30 meter pixels based on land cover and slope. The dasymetric data was aggregated by HUC_12 boundary to summarize population by watershed. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets). This dataset can be used to learn about the beneficiaries of the ecosystem services represented in the Atlas. It can be used to identify areas where there might be greater demand for ecosystem services, or study imbalances between ecosystem services and population. The overall goal of EnviroAtlas is to employ and develop the best available science to map indicators of ecosystem services production, demand, and drivers for the nation. completed EnviroAtlas Coordinator U.S. Environmental Protection Agency, Office of Research and Development-Sustainable and Healthy Communities Research Program, EnviroAtlas Geospatial Data Owner (919) 541-3832 109 T.W. Alexander Drive Research Triangle Park NC 27709 EnviroAtlas@epa.gov https://www.epa.gov/enviroatlas pointOfContact asNeeded Ecosystem Environment theme EPA GIS Keyword Thesaurus 12-digit HUCs Demand for Ecosystem Services Demographics Ecosystem Services EnviroAtlas Environment Environmental Atlas Human Modeling theme EnviroAtlas Alabama Arizona Arkansas California Colorado Connecticut Delaware Florida Georgia Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas United States Utah Vermont Virginia Washington Washington DC West Virginia Wisconsin Wyoming place None https://edg.epa.gov/EPA_Data_License.html otherRestrictions Use Constraints: None. Please check sources, scale, accuracy, currency and other available information. Please confirm that you are using the most recent copy of both data and metadata. Acknowledgement of the EPA would be appreciated. otherRestrictions Access Constraints: None. PUBLIC https://project-open-data.github.io/schema/#accessLevel Standard Technical Controls eng; USA environment -128.02839229 -65.20336449 22.7348894 51.6773602 2010-01-01 2011-01-01 This metric was calculated using the EnviroAtlas Dasymetric raster version from 2/8/2016. true Entity and Attribute Information Entity and Attribute Overview: The US Census Bureau collects population information through the decennial census. Though this information is collected from individual residents, the US Census Bureau aggregates this data into census blocks. Census blocks are statistical areas bounded by both visible features such as roads and streams, as well as invisible boundaries such as county or state limits. This aggregation generally assumes that the population is distributed uniformly across each census block. While this assumption is practical for the purposes of the census, it makes it very difficult to determine how many individuals within a census block live near roads, in floodplains, or face other potential exposures. Traditionally, maps from census data that calculate distance use the centroid of the census block as the starting point. In areas that have large census blocks, this may introduce errors when determining walking or driving distances for individuals. Dasymetric mapping is a geospatial technique that is used to more accurately distribute data assigned to arbitrary boundaries, such as census blocks, using additional information such as land cover types and uses. Using the National Land Cover Dataset (NLCD), the EnviroAtlas dasymetric population map assumes that individuals will not live in areas that are classified as open water, ice/snow, or wetlands. Areas with slopes greater than 25 percent were also considered uninhabitable. Vegetated and developed areas are considered habitable and are assigned an estimated population density based on their respective land cover class. EnviroAtlas uses this technique to create a more informed delineation of population estimates. These data provide the foundation for estimating walking distances, viewsheds, and exposure potential in many maps contained in EnviroAtlas. This map applies a dasymetric mapping technique to the 2010 US Census population data using land cover classes from the 2011 National Land Cover Dataset (10-10-2014 version). This data was then summarized by HUC12 unit boundaries. The NLCD classes were divided into five categories based on habitability. The following explains how the NLCD was reclassified, using this format: "Dasymetric Category: NLCD class (code)." *Non-habitable: Open water (11), perennial ice/snow (12), emergent herbaceous wetlands (95). *Habitable 1: Deciduous forest (41), evergreen forest (42), mixed forest (43), shrub/scrub (52), grassland/herbaceous (71), pasture/hay (81), cultivated crops (82), woody wetlands (90). *Habitable 2: Developed, open space (21). *Habitable 3: Developed, low intensity (22). *Habitable 4: Developed, medium intensity (23). *Habitable 5: Developed, high intensity (24). The NLCD data set does not explicitly identify roads and this can create issues in assigning population estimates to individual pixels, particularly in rural areas with large census blocks. Specifically, people do not reside in the middle of roads but rather along them. The EnviroAtlas method dealt with the issue by assuming that NLCD class 21 captures these rural roads. To this end, the NLCD class 21 was thinned using a 3x3 majority filter. Only NLCD class 21 was allowed to be changed, and only to the habitable 1 class. This allows for the removal of road pixels in forested or agricultural areas, but prevented changes from class 21 to another developed class in urban areas. The majority filters replace the value of a cell or pixel based on the values of the majority of their contiguous cells. The NLCD was then classified into non-habitable and five habitable classes discussed above. In addition, all slopes over 25% (calculated using NED) were masked as non-habitable. Small, narrow, and oddly shaped census blocks did not align well with the 2011 NLCD raster data - meaning that a centroid pixel from the NLCD could not be identified for these blocks. To deal with this, these small, narrow, and oddly shaped blocks were absorbed into neighboring census block polygons. The populations of the merged census blocks were added together and then assigned to the pixel level as a single block. Accounting for these small, narrow, and oddly shaped census blocks in this way prevented the loss of 100,000 people and 840 Km2 land area from the final data product. The final reclassified and masked land cover was then used with the 2010 census block boundaries and population counts as inputs to a series of python script tools in ArcGIS. Each habitable class required ten "pure" blocks of at least ten pixels, e.g. ten blocks of 100% habitable 1, ten blocks of 100% habitable 2, etc. Washington D.C. and Rhode Island did not have sufficient samples and were combined with Maryland and Massachusetts, respectively. Before final population allocation, the density for habitable 1 was set to 0.001 to force most population into developed land cover pixels. Final allocation was performed using: Equation 1: f_h2 = (a_h2 x d_h2)/(a_h1 x d_h1 + a_h2 xd_h2 + a_h3 x d_h3 + a_h4 x d_h4 + a_h5 x d_h5 ) Where f_h2 is the fraction of total population that is assigned to the habitable 2 pixels in the census block; d_h2, d_h3, d_h4, and d_h5 are the population densities for habitable classes 2 through 5 while a_h2, a_h3, a_h4, and a_h5 are the area percentages for habitable classes 2 through 5. f_h3, f_h4, f_h5 are calculated similarly. The Dasymetric Toolbox for ArcGIS v10 used to create these data can be downloaded from https://www.epa.gov/enviroatlas/dasymetric-toolbox. Entity and Attribute Detail Citation: https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets EnviroAtlas Coordinator U.S. Environmental Protection Agency, Office of Research and Development-Sustainable and Healthy Communities Research Program, EnviroAtlas Geospatial Data Owner (919) 541-3832 109 T.W. Alexander Drive Research Triangle Park NC 27709 EnviroAtlas@epa.gov https://www.epa.gov/enviroatlas distributor https://enviroatlas.epa.gov/download/CONUS_metrics_FGDB.zip download Download The URL providing direct access to the downloadable dataset. download https://enviroatlas.epa.gov/download/CONUS_metrics_CSV.zip ESRI:ArcGIS API The endpoint of a web service to access the dataset (REST endpoint, WMS GetCapabilities URL, or a SOAP WSDL endpoint). webMapService https://www.epa.gov/enviroatlas/enviroatlas-data information Documentation URL for accessing related documents such as data dictionary, technical information about a dataset, developer documentation, etc. information https://www.epa.gov/enviroatlas information Home Page Alternative landing page used to redirect user to a contextual, Agency-hosted "homepage" for the Dataset or API information dataset Horizontal Positional Accuracy Report Data were collected using methods that have unknown accuracy (EPA National Geospatial Data Policy [NGDP] Accuracy Tier 10). For more information, please see EPA's NGDP at https://www.epa.gov/geospatial/geospatial-policies-and-standards Features represented have not been tested for completeness Features represented have not been tested for completeness Tests for integrity have not been performed. This lineage was generated by the FGDC CSDGM to 19139 transformation Reclassify NLCD 2011 (10-10-2014 version) land cover - 11, 12, 31 and 95 (nodata), 21 (21), 22 (22), 23 (23), 24 (24), 41, 42, 43, 52, 71, 81, 82 , 90 (1). 2015-10-01T00:00:00 Use 3x3 majority filter to replace class 21 with class 1 to eliminate some rural roads. 2015-10-01T00:00:00 Mask slopes > 25% using 30 meter NED. 2015-10-01T00:00:00 Use the dasymetric tools for each state. Washington, D.C. was combined with Maryland to ensure adequate samples. Rhode Island was combined with Massachusetts for the same reason. Density for class 1 was set to 0.001 to force most population to urban classes (21-24). 2015-10-01T00:00:00 Merge results into one raster. 2015-10-01T00:00:00 Reclassify all NoData to 0 to fill "holes." 2015-11-01T00:00:00 Use the Census 1:500,000 US Counties to create a US Coastline. 2015-11-01T00:00:00 For Dasymetric pixels outside the coastline, convert 0's back to Nulls. For dasymetric pixels inside the coastline, maintain 0's as 0. 2015-11-01T00:00:00 Convert to TIFF for use in EnviroAtlas. 2015-11-01T00:00:00 Calculate Sum of population by HUC_12 using "Zonal Statistics as Table" tool in ArcGIS, with a rasterized version of the NHDPlusV2 WBD Snapshot - EnviroAtlas Version, snapped to the NLCD. 2018-01-24T00:00:00 unknown 2029-07-23 This metadata was automatically generated from the FGDC Content Standard for Digital Geospatial Metadata standard (version FGDC-STD-001-1998) using the 2024-02-09T11:11:00 version of the FGDC CSDGM to ISO 19139 transform. EnviroAtlas Coordinator U.S. Environmental Protection Agency, Office of Research and Development-Sustainable and Healthy Communities Research Program, EnviroAtlas Geospatial Data Owner (919) 541-3832 109 T.W. Alexander Drive Research Triangle Park NC 27709 EnviroAtlas@epa.gov https://www.epa.gov/enviroatlas pointOfContact