Channel Migration Areas in King County

Metadata also available as - [Outline]

Frequently anticipated questions:

What does this data set describe?

Title: Channel Migration Areas in King County
Abstract:
Channel migration hazards for seven King County rivers: Middle White River, Raging River, Tolt River, Three Forks area of Snoqualmie River, Cedar River, Green River, and the South Fork of the Skykomish River. The Cedar River was updated April 2015, the SF Skykomish June 2017, and the Tolt July 2018. In December 2019, the Middle White River was added, the Raging River was updated, and a revision was made to the updated Cedar CMZ.
Supplemental_Information:
There are several rapidly migrating river systems in King County. Studies (cited below) have been prepared by or for the King County Department of Natural Resources to map and describe areas of channel migration hazard on sections of seven King County rivers: middle White River, Raging River, Tolt River, Three Forks area of Snoqualmie River, Cedar River, Green River, and the South Fork of the Skykomish River. In each study, the maximum probable future limits of channel migration were defined using historic meander belt widths and other geomorphic features. Land within these limits is classified according to the relative degree of hazard from channel migration, based upon historic rates of channel migration and the presence of major bank protection structures that protect arterial roads and subdivisions.
  1. How should this data set be cited?

    County, King, 20050309, Channel Migration Areas in King County: King County, King County, WA.

    Online Links:

    Other_Citation_Details: None

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -122.240850
    East_Bounding_Coordinate: -121.301206
    North_Bounding_Coordinate: 47.778799
    South_Bounding_Coordinate: 47.146674

  3. What does it look like?

    <http://www5.kingcounty.gov/sdc/DataImages/chnlmigr.jpg> (JPG)
    JPG File of layer overlain on base of WA counties or local cities

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

    Calendar_Date: 07-Jan-2020
    Currentness_Reference: publication date

  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):

      • GT-polygon composed of chains (236)

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

      The map projection used is NAD 1983 HARN StatePlane Washington North FIPS 4601 Feet.

      Projection parameters:
      Standard_Parallel: 47.5
      Standard_Parallel: 48.73333333333333
      Longitude_of_Central_Meridian: -120.8333333333333
      Latitude_of_Projection_Origin: 47.0
      False_Easting: 1640416.666666667
      False_Northing: 0.0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.00025
      Ordinates (y-coordinates) are specified to the nearest 0.00025
      Planar coordinates are specified in foot_us

      The horizontal datum used is D North American 1983 HARN.
      The ellipsoid used is GRS 1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.

  7. How does the data set describe geographic features?

    maint.WLR.chnlmigr_area
    Feature attribute table. (Source: ESRI)

    OBJECTID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    HAZARD
    Level of channel migration hazard. (Source: King County)

    ValueDefinition
    MODERATEThe moderate hazard area is located between the outer boundary of severe hazard and the maximum probable limits of future migration.
    POTENTIALThe area is not yet a channel migration zone, but could become one.
    SEVEREThe severe hazard area includes the width of the river channel itself plus a width equal to one hundred (100) years times the average annual channel migration rate. It is assumed that channel will migrate for fifty (50) years on both sides of the present channel location during this hundred year period.

    SHAPE
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    Shape.STArea()

    Shape.STLength()

    Entity_and_Attribute_Overview:
    This dataset is polygons depticting the severity of the Channel Migration hazard for the Raging River, Tolt River, Three Forks area of Snoqualmie River, Cedar River, and Green River.
    Entity_and_Attribute_Detail_Citation: See Detailed Description section of Entity Attribute section.

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?

    See also Ken Zweig, DNRP/WLRD - Floodplain and River Management Program, 206-477-4732 for more details.

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

    King County IT, GIS Center
    Attn: Todd Klinka
    GIS Analyst
    201 S. Jackson St. Mailstop LSC-IT-225
    Seattle, WA 98104
    US

    206-477-4412 (voice)
    Todd.Klinka@kingcounty.gov

Why was the data set created?

This dataset can be use to estimate the channel migration for seven rivers: White River, Raging River, Tolt River, Three Forks area of Snoqualmie River, Cedar River, Green River, and the South Fork of the Skykomish River.

How was the data set created?

  1. From what previous works were the data drawn?

    P1993 (source 1 of 2)
    Perkins, S.J, 19930101, Green River Channel Migration Study.

    Other_Citation_Details:
    King County Department of Public Works, Surface Water Management Division, Seattle WA
    Type_of_Source_Media: hardcopyPaper
    Source_Contribution: Used to create data.

    P1996 (source 2 of 2)
    Perkins, S.J, 19960101, Channel Migration in the Three Forks Area of the Snoqualmie River.

    Other_Citation_Details:
    King County Department of Natural Resources, Surface Water Management Division, Seattle WA
    Type_of_Source_Media: hardcopyPaper
    Source_Contribution: Used to create data.

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

    Date: 15-Jun-2015 (process 1 of 4)
    Added Cedar River CMZ data 06/15/2015 Source data 04/15/2015

    Date: 01-Sep-2017 (process 2 of 4)
    The South Fork Skykomish Channel Migration Zone (CMZ) study and map were completed in 2017. The amended channel migration public rule adopting the South Fork Skykomish CMZ became effective in September 2017.

    Date: 13-Jul-2018 (process 3 of 4)
    The Tolt River CMZ study and map, completed in June 2017, and the January 16, 2018 Reassessment of the King County Channel Migration Zone Mapping near the Holberg Levee, Tolt River (Tolt River CMZ Reassessment Technical Memo) were incorporated into the final July 2018 Tolt River Channel Migration Zone (CMZ) map per 21A-24-279A(B)(3).

    The amended channel migration public rule became effective July 13, 2018

    Date: 25-Dec-2019 (process 4 of 4)
    The Raging River Channel Migration Zone (CMZ) study and map and Middle White River CMZ were completed in 2019. A smaller portion of the effective Cedar CMZ mapping was reassessed in 2019, resulting in an adjustment to the mapped hazard areas.

    The amended channel migration public rule became effective December 25, 2019.

  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?

    Unknown.

  2. How accurate are the geographic locations?

    CMZ boundaries typically have positional accuracy of 0-30 feet, in some areas with few control points such as eastern King County the positional accuracy could be as much as 50-100 feet. The data should not be reproduced or used at a scale larger than 1:2400.

  3. How accurate are the heights or depths?

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

    This dataset covers only the following areas of King County: middle White River, Raging River, Tolt River, South Fork Skykomish River, Three Forks area of Snoqualmie River, Cedar River, and Green River.

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

    This dataset meets standard coverage QA/QC checks such as labelerrors, nodeerrors.

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:
King County data are made available with the understanding that they shall be used exclusively by the obtainer or his/her authorized agents. Digital products may not be reproduced or redistributed in any form or by any means without the express written authorization of King County.

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

    KCGIS Center
    Attn: Cheryl Wilder
    Data Sales Coordinator
    201 S Jackson St, Suite 700
    Seattle, WA 980914
    US

    206-263-5220 (voice)

  2. What's the catalog number I need to order this data set?

    /plibrary2/hydro/shapes/polygon/chnlmigr.shp

  3. What legal disclaimers am I supposed to read?

    King County disclaims any warranty of use of any digital product or data beyond that for which it was designed.

  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 14-May-2021
Metadata author:
King County GIS Center
Attn: Fred Lott
Senior GIS Specialist
201 S Jackson St
Seattle, WA 98104

206-477-4758 (voice)

Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

Generated by mp version 2.9.12 on Wed Jun 01 09:54:45 2022