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This shapefile contains hydrologic unit code (HUC) boundaries in the Southern
United States and provides information about watershed condition. Maps watersheds.
used in figures 19.4 and 19.5
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General Supplemental Information: The shapefile covers the following states: AL, AR, FL, GA, KY, LA, MS, NC, SC, TN, TX, OK, and VA.
USGS Documented Supplemental Technical Information: Hydrologic Unit Code (HUC) areas in this file do not necessarily match those published in Water-Supply Paper 2294 (Seaber et al). The file has finer resolution than the maps used to determine areas published in the Water-Supply Paper.
USGS Documented Process Steps:
The original hydrologic unit boundaries file (HUCS10) was created through the following steps:
a) 1:2,000,000-scale stable-base map plots of drainage (streams) and the latitude/longitude grid were obtained from the USGS National Mapping Division (NMD). These plots were in the Lambert Conformal Conic projection, and used 1:500,000-scale State base map projection parameters. Fifteen sections were plotted using 1970 National Atlas 1:2,000,000-scale sectional boundaries.
b) Individual State 1:500,000-scale hydrologic unit maps in the Lambert Conformal Conic projection were photoreduced to 1:2,000,000. c) Hydrologic unit boundaries were compiled and the edges were matched on scale-stable 1:2,000,000 plots. The boundaries were combined with the streams plots for digitizing.
d) The hydrologic unit boundaries were digitized by Automated Datatron, Hyattesville, MD., which digitizes materials on contract for NMD.
e) Digital data from Automated Datatron was converted to an ARC/INFO coverage, then checked and corrected.
f) A detailed, annotated list was compiled, listing locations where hydrologic unit boundaries and streams were coincident, or where 1:2,000,000-scale DLG streams were in error. Wherever possible, conflicts and errors were resolved.
Source_Used_Citation_Abbreviation: HUCmaps Source_Used_Citation_Abbreviation: DLGHY Process_Date: 1985-1992 Source_Produced_Citation_Abbreviation: HUCS10
HUCS11 was created by modifying and correcting the HUCS10 file in ARC/INFO, and combining it with a 1:2,000,000-scale U.S. counties file to identify onshore and offshore areas. Other county attributes were excluded. This process was done in ARC/INFO, and used a fuzzy tolerance of 2 meters. A small part of the original map, which lay on top of part of the Canadian Great Lakes, was deleted. The attributes were renamed and expanded. Source_Used_Citation_Abbreviation: HUCS10 Source_Used_Citation_Abbreviation: DLGCO Process_Date: 1992 Source_Produced_Citation_Abbreviation: HUCS11
Process_Description: The HUCs_2M.TRACE file was created from the River Reach 1 (rf1) coverage, which includes a pointer to the next downstream segment of each reach. The resulting file was added to INFO, along with an index created using HUC_INDEX.AML. Source_Used_Citation_Abbreviation: HUCS11 Source_Used_Citation_Abbreviation: RF1 Process_Date: 1994 Source_Produced_Citation_Abbreviation: HUCS111
Using ARC/INFO, HUCS111 was compared with the most recent 1:2,000,000-scale streams file created by the USGS National Mapping Division (NMD) for inclusion in the National Atlas of the United States of America. Where a stream crossed a hydrologic unit boundary, the boundary was compared to the 1:500,000-scale State hydrologic unit map (Seaber). If a stream and hydrologic unit boundary intersection could not be resolved by this comparison, the USGS 1:100,000-scale topographic quadrangles were used. All corrected hydrologic unit boundaries were given a value of 5 for the Error_type attribute. The boundaries were changed by moving vertices to include the stream in the appropriate hydrologic unit. All editing was done on-screen. This step happened May 22, 1998 and November 10, 1998.
The Region, Subregion, Accounting unit, and cataloging unit names from Seaber were added to the data set and spot-checked. Values for BNDTYPE were determined from the bounding polygons using INDEX_HUC.AML. This same procedure also indexed the coverage on all user-defined items in the .PAT and .AAT files. A listing can be found in the file, HUCS_2M.AML_INDEX (imbedded in the INFO file).
The attributes Error_type, Reg_name, Map_label, Catalog_Unit_Nam, and Catalog_unit_num were added to the file. Two annotation layers were also added to the coverage. One layer is called anno.maplabel1, which shows the first six digits for each accounting unit. The labels for accounting Regions 1 though 9 have the "0" in front of the number. The second annotation layer is anno.catnum, and this layer has the last 2 digit codes for each cataloging unit. All numbers were checked manually on a 1:2,000,000-scale plot of the data set. The cataloging unit names were spot-checked. The file was modified to agree with the official National Atlas coastline (NAStates).
The ARC/INFO coverage was exported to create the shapefiles and SDTS files. Source_Used_Citation_Abbreviation: HUCS111 Source_Used_Citation_Abbreviation: Seaber Source_Used_Citation_Abbreviation: HUCAKmap Source_Used_Citation_Abbreviation: NAStates Source_Used_Citation_Abbreviation: NAHydro Process_Date: 1998
Data Modifications by US Environmental Protection Agency Staff:
Nov. 2000: The coverage was downloaded by US Environmental Protection Agency personnel in compressed Arc Info Export format along with their associated metadata. The coverages were then reprojected and clipped to match Assessment standard Albers projection and State Assessment coverage boundary coordinates. This process used the Arc Info PROJECT and CLIP command. The coverage then exported as a shapefile.
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created: 25-Sep-2003 |