Huc_8 : Eight Digit Hydrologic Unit Code - (REQUIRED) A unique 8-digit code from the USGS map series "Hydrologic Unit Maps". The same number was used in every record that pertains to a subwatershed that resides within the same 8-digit sub-basin.Numbers were assigned in an upstream to downstream fashion. Where no downstream/upstream relationship could be determined numbers were assigned in a clockwise fashion.
Huc_10: Ten Digit Hydrologic Unit Code - (REQUIRED) This field provides a unique 10-digit code for each watershed. This same number was used in every record that pertains to a subwatershed that resides within the same 10-digit watershed. Numbers were assigned in an upstream to downstream fashion. Where no downstream/upstream relationship could be determined numbers were assigned in a clockwise fashion.
Huc_12: Twelve Digit Hydrologic Unit Code - (REQUIRED) This field provides a unique 12-digit code for each subwatershed. Numbers were assigned in an upstream to downstream fashion. Where no downstream/upstream relationship could be determined numbers were assigned in a clockwise fashion.
Acres: Acres - (REQUIRED) Area of subwatershed including non-contributing areas calculated to acres as a whole number, no decimals. The "Acres" field was calculated from the "Area" field.
States: States - (REQUIRED) The "States" field includes the names of all state(s) that the subwatershed falls within. The 2-digit postal abbreviation in upper case and in alphabetical order was used, separated with a comma.
Ncontrb_a: Non-Contributing Area - (FIELD REQUIRED, ATTRIBUTES OPTIONAL) Drainage areas that do not flow toward the outlet of any hydrologic unit are considered non-contributing. If a non-contributing area is on the boundary between two or more hydrologic units, the non-contributing area is associated with the hydrologic unit adjacent to the low point on the boundary. This attribute should be the total of the non-contributing areas within a hydrologic unit calculated in acres.
Hu_10_ds: Fifth Level Downstream Hydrologic Unit Code - (FIELD REQUIRED, ATTRIBUTES OPTIONAL) This field has the 10-digit code of the 5th level hydrologic unit that is receiving the majority of the flow from the watershed that the 6th level HU falls within. Outlets created by ditching or other artificial drainage were not considered for this field. If an HU flows into an ocean or the Gulf of Mexico, this field was populated with "OCEAN" and if a HU flows into one of the Great Lakes the term "LAKE" was used. If a HU flows across international borders, "CANADA" or "MEXICO" was used depending on which country the HU drains into. If an HU is a closed basin, then the term "CLOSED BASIN"was used.
Hu_10_name: Fifth Level Hydrologic Unit Name - (FIELD REQUIRED, ATTRIBUTES OPTIONAL) This field used officially recognized names only. This field was populated by following the directions in subsection 6.3 "Watershed and Subwatershed Naming Protocol". The name used to attribute the watershed was used only once within a 4th level unit.
Hu_10_mod: Fifth Level Hydrologic Unit Modifications - (REQUIRED) This field identifies any type of modifications to natural overland flow that alters the location of the hydrologic unit boundary for a 10-digit watershed. This field shows the most significant to least significant modification(s) to the watershed boundary. One or more of the following abbreviations was used. SC - Stormwater Canal ID - Irrigation Ditch IT - Interbasin Transfer BC - Barge Canal SD - Stormwater Ditch PD - Pipe Diversion CD - Channel Diversion NC - Non-Contributing KA - Karst LE - Levee NM - No Modifications OC - Overflow Channel DM - Dam at outlet or HU boundary OT - Other
Hu_10_type: Fifth Level Hydrologic Unit Type - (REQUIRED) This field was populated with the hydrologic unit type from the list provided that most closely identifies the watershed. S - "Standard" hydrologic unit - Any land HU with drainage flowing to a single outlet point, excluding non-contributing areas. This includes areas or small triangular wedges between adjacent HU's that remain after classic hydrologic units are delineated. Some examples include "true", "classic", "composite", and "remnant" hydrologic units. C - "Closed Basin" hydrologic unit - A drainage area that is 100% non-contributing. This means all surface flow is internal, no overland flow leaves the hydrologic unit through the outlet point. F - "Frontal" hydrologic unit - Areas along the coastline of lakes, oceans, bays, etc. that have more than one outlet. These HU's are predominantly land with some water areas at or near the outlet(s). W - "Water" hydrologic unit - Hydrologic units that are predominantly water with adjacent land areas, ex. lake, easturies, harbors. I - "Island" hydrologic unit - A hydrologic unit that is one or more islands and adjacent water out to the toe of the shore face. U - "Unclassified" hydrologic unit - A hydrologic unit that can't be defined or doesn't fit into one of the types that have been listed.
Hu_12_ds: Sixth Level Downstream Hydrologic Unit Code - (FIELD REQUIRED, ATTRIBUTES OPTIONAL) This field was populated with the 12-digit code of the 6th level hydrologic unit that is receiving the majority of the flow from the subwatershed. Outlets created by ditching or other artificial drainage were not considered for this field. If a HU flows into an ocean or the Gulf of Mexico it was populate with "OCEAN" and if a HU flows into one of the Great Lakes the term "LAKE" was used. If a HU flows across international borders, "CANADA" or "MEXICO" was used depending on which country the HU drains into. If an HU is a closed basin, this field was populated with the term "CLOSED BASIN".
Hu_12_name: Sixth Level Hydrologic Unit Name - (FIELD REQUIRED, ATTRIBUTES OPTIONAL) Officially recognized names were used in this field. This field was populated by following the directions in subsection 6.3 "Watershed and Subwatershed Naming Protocol". The name used to attribute the subwatershed was used only once within a 4th level unit.
Hu_12_mod: Sixth Level Hydrologic Unit Modifications - (REQUIRED) This field identifies any type of man-made modification(s) to natural overland flow that alters the location of the hydrologic unit boundary for a 12-digit subwatershed. One or more of the following abbreviations was chosen for this field. SC - Stormwater Canal ID - Irrigation Ditch IT - Interbasin Transfer BC - Barge Canal SD - Stormwater Ditch PD - Pipe Diversion CD - Channel Diversion NC - Non-Contributing KA - Karst LE - Levee NM - No Modifications OC - Overflow Channel DM - Dam at outlet or HU boundary OT - Other
Hu_12_type: Sixth Level Hydrologic Unit Type - (REQUIRED) This field was populated with the hydrologic unit type from the list provided that most closely identifies the subwatershed. S - "Standard" hydrologic unit - Any land HU with drainage flowing to a single outlet point, excluding non-contributing areas. This includes areas or small triangular wedges between adjacent HU's that remain after classic hydrologic units are delineated. Some examples include "true", "classic", "composite", and "remnant" hydrologic units. C - "Closed Basin" hydrologic unit - A drainage area that is 100% non-contributing. This means all surface flow is internal, no overland flow leaves the hydrologic unit through the outlet point. F - "Frontal" hydrologic unit - Areas along the coastline of lakes, oceans, bays, etc. that have more than one outlet. These HU's are predominantly land with some water at or near the outlet(s). W - "Water" hydrologic unit - Hydrologic units that are predominantly water with adjacent land areas, ex. lake, easturies. I - "Island" hydrologic unit - A hydrologic unit that is one or more islands and adjacent water out to the toe of the shore face. U - "Unclassified" hydrologic unit - A hydrologic unit that can't be defined or doesn't fit into one of the types that have been listed.
2) Line attributes
Hu_level: Hydrologic Unit Level - (REQUIRED) This field provides the means to create cartographically pleasing maps. This field is populated with the highest hydrologic unit level (smallest number) for the line (arc) represented by the record. The attribute was recorded using numbers 1 through 6 representing each level with 1 being the highest and 6 the lowest level. An example would be if a line represents a region, subregion, basin, subbasin, watershed, and subwatershed boundary, then this cell was populated with a 1 (Region). Below is a list of numbers used for each level.
Level Digit# Name 1 2 Region 2 4 Subregion 3 6 Basin 4 8 Subbasin 5 10 Watershed 6 12 Subwatershed
Linesource: Line Spatial Data Source - (REQUIRED) The Linesource indicates the base map source(s) used to delineate at 1:24,000 scale. The field was populated using one of the standardized code(s) listed below. If more than one code was used, then a comma was used to separate the codes. TOPO24 - Delineation from hardcopy 1:24,000 scale topographic maps TOPO25 - Delineation from hardcopy 1:25,000 topgraphic maps, only Alaska and Caribbean TOPO63 - Delineation from hardcopy 1:63,360 topographic maps, only Alaska and Caribbean DRG24 - Delineation from 1:24,000 scale Digital Raster Graphics DRG25 - Delineation from 1:25,000 Digital Raster Graphics, only Alaska and Caribbean DRG63 - Delineation from 1:63,360 Digital Raster Graphics, only Alaska and Caribbean DEM10 - Derived from 10 meter Digital Elevation Model DEM30 - Derived from 30 meter Digital Elevation Model NED30 - Derived from 30 meter National Elevation Dateset Model EDNA30 - (formally NED-H), derived from 30 meter Elevation Derivatives for National Applications BATH"scale" (ex. BATH24) - Interpreted from NOAA 1:24,000 scale bathymetric data HYPSO"scale" (ex. HYPSO24)- Delineated from 1:24,000 scale contour data ORTHO"scale" (ex. ORTHO12) - Interpreted from 1:12,000 scale Ortho-imagery DEDEM10 - Drainage enforced 10 meter Digital Elevation Model DEDEM30 - Drainage enforced 30 meter Digital Elevation Model GPS - Derived from Global Positioning System LIDAR - Derived from LIDAR IFSAR - Derived from IFSAR data OTH - Other UNK - Unknown All other reference and source maps not listed should be noted in the metadata. Meta_id: Metadata ID Number - (REQUIRED) The Metadata ID is a code that identifies which metadata file applies to the arc. In most cases there is only one metadata file. However, in some cases more than one metadata file was used to identify different groups and/or procedures used to produce the lines. The metadata ID is a 4-character code starting with the 2-letter state postal code, followed by a 2-digit sequence number. For example "OK01", "ID02", etc