Paper No. 16-10
Presentation Time: 10:45 AM
COLLABORATION ON LANDSLIDE HAZARD MAPPING PROTOCOLS IN WASHINGTON STATE
BETHEL, John P., King County Dept. of Natural Resources and Parks, Water and Land Resource Div, 201 S. Jackson, suite 600, Seattle, WA 98104, SLAUGHTER, Stephen L., Washington State Department of Natural Resources, Washington Geological Survey, 1111 Washington Street SE, MS 47007, Olympia, WA 98504-7007 and WESSEL, Gregory R., Geology In The Public Interest, PO Box 1135, Vashon, WA 98070
The catastrophic Oso landslide took place on March 22nd 2014 in Snohomish County, Washington State. In response to this event, King County (immediately south of Snohomish County) initiated a mapping program to more accurately characterize the landslide hazards and risks to County residents. During the initial phases of this program, King County staff worked with the Washington State Department of Natural Resources, Division of Geology and Earth Resources (DGER) hazards program to investigate opportunities for state-wide collaboration with other counties and some cities. DGER staff proposed creation of a Landslide Hazard Working Group composed of participants from counties and cities across the state. The purpose of this group is to evaluate and coordinate landslide hazard mapping methods, and agree on standard landslide nomenclature and characterization so as to create consistent, comparable landslide hazard maps state-wide.
Because of variations in geology, topography, and climate across the state, landslide hazard assessments must deal with a range of mass-wasting phenomenon including: deep-seated ancient landslides (which may be subject to reactivation), shallow rapid landslides, debris flows, rock falls, and complex combinations of these failure types. Landslide hazard mapping also needs to address potential runout from the processes listed above, and the consequences of landslide dam formation where landslide deposits enter stream channels.
The Landslide Hazard Mapping Working Group has only begun investigating approaches to this task. Initial efforts are focused on: evaluating mapping approaches for identifying areas at risk from shallow landsliding, developing a consistent protocol for landslide characterization from Lidar imagery, developing a standard format for characterizing landslides in the field, and agreeing on a format and platform for sharing landslide data.
The Landslide Hazard Mapping Working Group establishes an innovative framework that can be used to address a number of concerns on a regional scale. The tasks at hand are not trivial, but the potential benefits, both scientific and financial, of working together for a common geologic goal are substantial.
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