Landslide Hazards along River Corridors - Top of internal landslides (steep slopes on top of a smaller slide within a larger slide)

Description

Layer name: LSR_DS_TOPOFINTERNALSCARP
Subject category: enviro
Title: Landslide Hazards along River Corridors - Top of internal landslides (steep slopes on top of a smaller slide within a larger slide)
Feature Count: 1503
Feature Type: Line
Abstract: Where fluvial or coastal erosion has created steep, high slopes in glacial sediments, these slopes sometimes fail in large, deep-seated landslides. The segregation of landslides into deep and shallow is somewhat arbitrary and different investigators have used different criteria to differentiate these landslides. For this project, the differentiation follows the criteria proposed by Burns and Madin (2009) that deep-seated slides extend to a depth of more than 15 ft. (4.6 m.). In general this corresponds to individual landslides which are large enough to be distinct on hillshade images generated from LiDAR data. For this mapping, deep-seated landslides may include features where the failure plane is more than 15 ft. deep or where landslide debris accumulates to a depth of more than 15 ft. In King County, a variety of landslide types occur at a scale that may create deep-seated landslides.
Purpose: Suitable for general reference and analyses. Identifies only the top of the internal landslides (steep slopes on top of a smaller slide within a larger slide) identified on deep seated landslides mapped within the river corridor study limits in King County.
Status: Complete
Updated: None planned
Time period of content: (single date,as YYYYMMDD):: 20151230
Time period of content: (date range, as YYYYMMDD):: -
Spatial reference: WA State Plane North
FGDC Documentation: Classic or FAQ
Open Data Availability: Yes
Place Keywords: Pacific NW, King County, WA, Washington state,
Theme Keywords: enviro, Pacific NW, King County WA, Washington state, landslide, slide, mass movement, landslide hazard mapping, debris slides, shallow landslides, shallow landsliding, debris sliding,
Lineage: Not available
Supplemental Information: King County retained Shannon & Wilson to map deep-seated landslides within the study limits using the procedure in the Oregon State Department of Geology and Mineral Industries (OR DOGAMI) Special Paper 42 (Burns and Madin 2009). Shannon and Wilson mapped 930 deep-seated landslides in the study area during this work. A report prepared by Shannon & Wilson to accompany their mapping is included as Appendix A of the report. Many features of deep-seated landslides share similar topographic characteristics including steep, often arcuate head scarps defining the upslope limit of the slide and a distinct deposit of displaced debris downslope. The debris was often identifiable by its lobate form and hummocky upper surface. These features varied in their topographic distinctness from features that appeared sharp and unambiguous to features that were muted and subtle. It is likely that some features mapped as slides based on their topographic character may have formed in other ways and it is also likely that some prehistoric deep-seated landslides present in the study limits were not identified because they were not distinguishable with the available imaging. A numerical confidence rating method set by the DOGAMI method (e.g., headscarp and slide morphology) was used to assign ratings to each mapped landslide. Twenty attributes, i.e. relative age of landslide, LiDAR source and date, and whether the slide appeared natural or human modified, of each landslide, were documented.

Contacts

Maintained by:
King County King County Dept of Natural Resources and Parks, Water and Lands Resource Division
Primary: Ken Rauscher, GIS Analyst, 206-477-4414
(How to e-mail a County contact)
Secondary: KCGIS Center; giscenter@kingcounty.gov. This mailbox is monitored during business hours.

Attribute Information

Constraints

Access: Access Constraint: Data is not available on GIS Data Portal, it may be available via a custom data request

Use: 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.