Landslide Hazards along River Corridors - Shallow Debris Slides Severe Hazard Potential

Metadata also available as - [Outline]

Frequently anticipated questions:


What does this data set describe?

Title:
Landslide Hazards along River Corridors - Shallow Debris Slides Severe Hazard Potential
Abstract:
Shallow debris slides are a common style of slope movement both in the Puget Lowland and Cascade Mountains. Shallow debris slides are characterized by failure of a relatively shallow layer of soil typically sliding on a surface of more competent material, either bedrock or dense glacial sediments. Shallow debris slides are typically 3 to 6 feet (1 to 2 meters) and translational. Shallow colluvial soils on slopes are formed through a variety of processes, including breaking up of the underlying in-place substrate (either bedrock or Quaternary sediments) by freeze/thaw, wetting/drying, bioturbation, and chemical weathering. Soils on steep slopes in King County vary significantly with respect to soil thickness, soil strength, and hydraulic properties; this variability presents the central challenge in assessing their stability across a landscape. Shallow debris slides are widespread across the landscape and are common occurrences during periods of high rainfall in both mountain and lowland settings. Shallow debris slides are often triggered by intense rainfall or, in developed areas, discharge of stormwater onto a steep slope. The potential for shallow debris slides is often increased by other human activities including vegetation removal (including logging) and inappropriate fill placement. Although comparatively small in scale, shallow debris slides can occur on almost any steep slopes anywhere on the landscape. Because this type of landslide is shallow in depth and small in lateral extent, the debris often does not travel a long distance — unless it transitions into a debris flow. But the debris is typically saturated, can move quickly, and often carrying logs or entire trees. Impact and inundation by such debris can be highly destructive in the area of deposition.
Supplemental_Information:
The stability of slopes with respect to shallow debris failures is often evaluated using a simple limit equilibrium analysis known as the infinite slope model. The infinite slope model is the only commonly used quantitative slope stability model applicable across an entire landscape. For this DNRP mapping project, an infinite slope analysis was used to generally identify slopes potentially subject to shallow debris slides. Soil strength parameters were estimated by measuring the inclination of 45 valley-wall slopes in the study limits that were relatively straight in profile. Following the DOGAMI protocol (Burns et al. 2012), slopes of 24 degrees to 28 degrees (44 to 54 percent) were identified as having a FOS between 1.25 and 1.5 and having a moderate hazard of being subject to shallow debris slides. Slopes steeper than 28 degrees (54 percent) were identified as having a FOS of less than 1.25 and having a severe hazard of being subject to shallow debris slides.
  1. How should this data set be cited?

    County, King, 20160816, Landslide Hazards along River Corridors - Shallow Debris Slides Severe Hazard Potential: King County, King County, WA.

    Online Links:

    Other_Citation_Details: None

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -122.304239
    East_Bounding_Coordinate: -121.131347
    North_Bounding_Coordinate: 47.781334
    South_Bounding_Coordinate: 47.426542

  3. What does it look like?

    <http://www5.kingcounty.gov/sdc/DataImages/lsr_sds_sevhazpot.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: 20-Jun-2016
    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 (0)

    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 0.000000026366619998441372
      Ordinates (y-coordinates) are specified to the nearest 0.000000026366619998441372
      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?

    Shallow Debris Slides Severe Hazard Potential
    area data table (Source: King County)

    OBJECTID
    Internal feature number. (Source: Esri)

    Sequential unique whole numbers that are automatically generated.

    gridcode
    (Source: King County)

    MapBy
    Author of mapped shapes (Source: King County)

    ValueDefinition
    KC DNRP 

    MapMethod
    Method used to identify moderate and severe potential for shallow debris slides (Source: King County)

    ValueDefinition
    Infinite Slope and OR DOGAMI Spec. Paper 45 

    LiDARSrc
    Source LiDAR imagery and date (Source: King County)

    ValueDefinition
    KC GIS 07/2016 

    TypeHaz
    Identifies severe potential for shallow debris slides (Source: King County)

    Shape
    Feature geometry. (Source: Esri)

    Coordinates defining the features.

    Shape.area

    Shape.len

    Entity_and_Attribute_Overview: Shallow Debris Slides Severe Hazard Potential
    Entity_and_Attribute_Detail_Citation: King County


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?

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

    King County King County Dept of Natural Resources and Parks, Water and Lands Resource Division
    Attn: Ken Rauscher
    GIS Analyst
    201 S Jackson St, Suite 706
    Seattle, WA 98104
    US

    206-477-4413 (voice)


Why was the data set created?

Suitable for general reference and analyses. Identifies only areas of potential shallow debris landsliding along the river corridor within the study limits in King County.


How was the data set created?

  1. From what previous works were the data drawn?

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

    Date: 15-Sep-2016 (process 1 of 1)
    generated from a raster data

  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?

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

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

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


How can someone get a copy of the data set?

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

Access_Constraints:
Access Constraint: Data is not available on GIS Data Portal, it may be available via a custom data request
Use_Constraints:
Use Constraint: 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 706
    Seattle, WA 98104
    US

    206-477-4421 (voice)

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

    /plibray2/enviro/shapes/polygon/lsr_sds_sevhazpot.shp

  3. What legal disclaimers am I supposed to read?

    Distribution Liability: 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: 04-Nov-2016
Metadata author:
King County King County Dept of Natural Resources and Parks, Water and Lands Resource Division
Attn: Ken Rauscher
GIS Analyst
201 S Jackson St, Suite 706
Seattle, WA 98104
US

206-477-4414 (voice)
firstname.lastname@kingcounty.gov

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


Generated by mp version 2.9.12 on Sat Apr 06 04:38:01 2019