GIS Data Catalog
Landslide Hazards along River Corridors - Shallow Debris Slides Severe Hazard Potential
Learn how to use GIS Open Data 🗺
Summary
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.
Description
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.
Layer information
| Layer Name | lsr_sds_sevhazpot_area |
| Subject Category | Environment |
| Title | Landslide Hazards along River Corridors - Shallow Debris Slides Severe Hazard Potential |
| Feature Count | 483324 |
| Feature Type | Polygon |
| Next Update | None planned |
| Spatial reference | EPSG:2926 |
| Control ID | 2573 |
| 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 |
| 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. |
Table Preview
Attribute information
|
OBJECTID
From Esri |
Description
Internal feature number. DomainSequential unique whole numbers that are automatically generated. |
|
gridcode
From King County |
Description
Not Found DomainNot Found |
|
MapBy
From King County |
Description
Author of mapped shapes DomainKC DNRP |
|
MapMethod
From King County |
Description
Method used to identify moderate and severe potential for shallow debris slides DomainInfinite Slope and OR DOGAMI Spec. Paper 45 |
|
LiDARSrc
From King County |
Description
Source LiDAR imagery and date DomainKC GIS 07/2016 |
|
TypeHaz
From King County |
Description
Identifies severe potential for shallow debris slides DomainNot Found |
|
Shape
From Esri |
Description
Feature geometry. DomainCoordinates defining the features. |
|
Shape.STArea()
From SQL Server |
Description
Returns the area of a geometry instance in square units, based on the spatial reference identifier (SRID) of the geometry. DomainDouble |
|
Shape.STLength()
From SQL Server |
Description
Returns the total length of the elements in a geometry instance. DomainDouble |
Contact information
| Maintained by | DNRP - Water and Land Resources |
| Primary |
Harkeerat Kang
Harkeerat.Kang@kingcounty.gov |
Terms of Use
| License | Terms of use and copyright |
Use this Data
|
Links
How to use in ArcGIS Pro |
|
| Sharing Status | Public |
Summary
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.
Description
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.
Contact information
| Maintained by | DNRP - Water and Land Resources |
| Primary |
Harkeerat Kang
Harkeerat.Kang@kingcounty.gov |
Terms of use and copyright
| License | Terms of use and copyright |
Change history
| 9/15/2016 |
generated from a raster data |