Hydrologic Units for Alaska (fourth level HUC)

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Frequently anticipated questions:


What does this data set describe?

Title: Hydrologic Units for Alaska (fourth level HUC)
Abstract:
This shapefile displays the 8-digit hydrologic units for the Alaska sub-basins. This data was developed in response to a need for hydrologic units of a more manageable size than currently exist.
This data set consists of geo-referenced digital map data and associated attributes. The hydrologic unit code attached to each delineated polygon is linked to the attribute data, which can contain information on area in acres, non-contributing area, state(s) the HU falls within, and name.
  1. How should this data set be cited?

    Alaska Geographic Data Committee (AGDC), Unpublished Material, Hydrologic Units for Alaska (fourth level HUC).

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -180.000000
    East_Bounding_Coordinate: 180.000000
    North_Bounding_Coordinate: 71.407515
    South_Bounding_Coordinate: 49.128799

  3. What does it look like?

    \\ilmakso0db10\metadata\documents\images\huc_4th_level.png (png)
    Fourth level HUC

  4. Does the data set describe conditions during a particular time period?

    Calendar_Date: unknown
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • G-polygon (136)

    2. What coordinate system is used to represent geographic features?

      The map projection used is Albers Conical Equal Area.

      Projection parameters:
      Standard_Parallel: 55.000000
      Standard_Parallel: 65.000000
      Longitude_of_Central_Meridian: -154.000000
      Latitude_of_Projection_Origin: 50.000000
      False_Easting: 0.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.001723
      Ordinates (y-coordinates) are specified to the nearest 0.001723
      Planar coordinates are specified in meters

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.

  7. How does the data set describe geographic features?

    huc_level_4
    4th level hydrologic units. The watersheds follow the protocols as prescribed by federal guidelines. (Source: AGDC)

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    objectid
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    huc_code
    Fourth Level Hydrologic Unit Code (Source: U.S. Department of Commerce, 1983, Codes for Identification of Hydrologic Units in the US)

    ValueDefinition
    19010101,19010102,19010103,19010201,19010202,19010203,19010204,19010301,19010302,19010303,19010401,19010402,19020101,19020102,19020103,19020104,19020201,19020202,19020301,19020302,19020401,19020402,19020501,19020502,19020503,19020504,19020505,19020601,19020602,19020701,19020702,19030101,19030102,19030103,19030104,19030201,19030202,19030203,19030204,19030205,19030206,19030301,19030302,19030303,19030304,19030305,19030401,19030402,19030403,19030404,19030405,19030501,19030502,19030503,19040101,19040102,19040103,19040104,19040201,19040202,19040203,19040204,19040205,19040301,19040302,19040303,19040304,19040401,19040402,19040403,19040404,19040501,19040502,19040503,19040504,19040505,19040506,19040507,19040508,19040509,19040510,19040511,19040601,19040602,19040603,19040604,19040605,19040606,19040607,19040608,19040609,19040701,19040702,19040703,19040704,19040705,19040801,19040802,19040803,19040804,19040805,19050101,19050102,19050103,19050104,19050105,19050201,19050202,19050203,19050301,19050302,19050303,19050304,19050401,19050402,19050403,19050404,19050405,19060101,19060102,19060103,19060201,19060202,19060203,19060204,19060205,19060301,19060302,19060303,19060304,19060401,19060402,19060403,19060501,19060502,190605034th level HUC codes for Alaska

    shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    AGDC, EDNA, USGS

  3. To whom should users address questions about the data?

    Dennis Tol
    Alaska Bureau of Land Management
    Project Manager
    222 West 7th Avenue #13
    Anchorage, Alaska 99513-7599
    USA

    907-271-3348 (voice)
    907-271-5479 (FAX)
    dennis_tol@ak.blm.gov

    Hours_of_Service: 8:30 am - 4:30 pm


Why was the data set created?

The dataset was developed as a statewide effort to produce smaller more manageable watershed units for the state of Alaska. Through an interagency agreement the AGDC has undertaken an effort to produce 4th level hydrologic units following national guidelines.The hydrologic unit boundaries provide a uniquely identified and uniform method of subdividing large drainage areas. These hydrologic units are useful in many programs supported by various agencies. This project is managed by the Bureau of Land Management (BLM).
This data set is intended as a tool for water-resource management and planning activities, particularly for site-specific and localized studies, which require the amount of detail provided by a large-scale map.


How was the data set created?

  1. From what previous works were the data drawn?

    NHD (source 1 of 3)
    U.S. Geological Survey, Unpublished Material, National Hydrography Dataset.

    Online Links:

    Type_of_Source_Media: online
    Source_Scale_Denominator: 63360
    Source_Contribution:
    Provided a hydrography data layer to assist in determinining the drainage of the hydrologic units to be delineated.

    CU Boundaries (source 2 of 3)
    U.S. Geological Survey, Unpublished Material, Catalog Unit Boundaries.

    Online Links:

    Type_of_Source_Media: online
    Source_Scale_Denominator: 250000
    Source_Contribution:
    The delineated hydrologic units are to nest within 4th level catalog unit boundaries.

    DRG (source 3 of 3)
    U.S. Geological Survey, Unpublished Material, DRG.

    Type_of_Source_Media: disc
    Source_Scale_Denominator: 63360
    Source_Contribution:
    As prescribed by the Federal Standards For Delineation Of Hydrologic Boundaries the DRG's are to serve as a control for delineation of hydrologic unit boundaries.

  2. How were the data generated, processed, and modified?

    Date: Unknown (process 1 of 1)
    The technicians used tools provided by EDNA, DRG's, NHD and existing catalog unit boundaries as a basis for delineating hydrologic unit boundaries.

  3. What similar or related data should the user be aware of?


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    The attributes were proofed by the technicians at the time of input and checked for incorrect or inappropriate data. The attribute format follows the guidelines as prescribed by the Federal Standards For Delineation of Hydrologic Unit Boundaries.

  2. How accurate are the geographic locations?

    Statements of horizontal positional accuracy are based on accuracy statements made for U.S. Geological Survey topographic quadrangle maps. These maps were compiled to meet National Map Accuracy Standards. The accuracy of these maps is generally based on the contour information or DEM data available for the base maps.
    The watershed shapefile was georeferenced to the 1:63360 DRG as required by federal guidelines.The differences in positional accuracy between the hydrologic unit boundaries and their digitized map locations is unknown. Hydrologic unit boundaries generally were digitized within 0.01 inches of their locations on the digitizing source.

  3. How accurate are the heights or depths?

    Statements of vertical positional accuracy for elevation of water surfaces are based on accuracy statements made for U.S. Geological Survey topographic quadrangle maps. These maps were compiled to meet National Map Accuracy Standards. For vertical accuracy, this standard is met if at least 90 percent of well-defined points tested are within one-half contour interval of the correct value. Elevations of water surface printed on the published map meet this standard; the contour intervals of the maps vary. These elevations were transcribed into the digital data; the accuracy of this transcription was checked by visual comparison between the data and the map.

  4. Where are the gaps in the data? What is missing?

    The data is based on the National Hydrography Dataset, Digital Elevation Models (60m pixels) and U.S. Geological Survey topographic maps. The completeness of the data reflects the content of the sources. Features found on the ground may have been eliminated or generalized on the source graphics because of scale and legibility constraints.
    In the NHD, generally streams longer than one mile (approximately 1.6 kilometers) were collected. Most streams that flow from a lake were collected regardless of their length. Lake/ponds having an area greater than 6 acres approximately 2.4 hectares) were collected. Swamp/marsh features were not collected. Note, however, that these general rules were applied unevenly among maps during compilation. Some map quadrangles have a much sparser pattern of hydrography than do adjoining maps and these differences continue in the digital rendition of these features. Near the international boundary with Canada, only the parts of features within the United States are delineated.

  5. How consistent are the relationships among the observations, including topology?

    The tests of logical consistency are performed using vendor software.


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Use_Constraints:
Acknowledgment of the originating agencies would be appreciated in products derived from these data.

  1. Who distributes the data set? (Distributor 1 of 1)

    Dennis Tol
    Bureau of Land Management
    Project Manager
    222 West 7th Avenue #13
    Anchorage, Alaska 99513-7599
    USA

    907-271-3348 (voice)
    907-271-5479 (FAX)
    dennis_tol@ak.blm.gov

    Hours_of_Service: 8:30 am - 4:30 pm
  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    No warranty is made by the Alaska Geographic Data Committee as to the accuracy, reliability, or completeness of these data for individual use or aggregate use with other data. The Alaska Geographic Data Committee is not liable for the misuse of date. Nor is it liable for damage, transmission of viruses, or computer contamination through the distribution of these data sets.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 05-Jul-2007
Last Reviewed: 05-Jul-2007
To be reviewed: 05-Jul-2008
Metadata author:
Dennis Tol
Alaska Bureau of Land Management
Project Manager
222 West 7th Avenue #13
Anchorage, Alaska 99513-7599
USA

907-271-3348 (voice)
907-271-5479 (FAX)
dennis_tol@ak.blm.gov

Hours_of_Service: 8:30 am - 4:30 pm
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:


Generated by mp version 2.9.12 on Thu Mar 09 14:07:53 2017