The objective of this report is to assist city and emergency management officials in evaluating the suitability of existing evacuation routes and assembly areas for potential vulnerability to ground failure from a M9+ CSZ earthquake. Results of this report could necessitate modifying, adding, or removing current evacuation routes and assembly areas. This report is not intended as a stand-alone geotechnical resource and does not involve an investigation into the performance of the built environment. However, understanding which areas are more vulnerable to ground failure during a large earthquake can help communities prepare for potentially obstructed transportation networks, toppled buildings, and other secondary seismic hazards. Likewise, we present no estimate of the damage resulting from liquefaction; in some instances, liquefaction may occur without causing significant ground displacement and consequent damages to structures.
The Washington Division of Geology and Earth Resources (WADGER) participates in the National Tsunami Hazard Mitigation Program to assess tsunami hazards along the Washington coast, particularly those generated by nearby faults such as the Cascadia subduction zone (CSZ). Currently, many coastal communities have tsunami evacuation routes and assembly areas based on mapping of potential inundation areas from a tsunami initiated by a CSZ earthquake on the Washington coast (WADGER, 2007a,b, 2012; Walsh and others, 2000, 2002a,b, 2003, 2005). These evacuation routes and evacuation areas had not been compared to areas of potential ground failure that could initiate from a CSZ earthquake. Earthquake-induced ground failures could adversely affect tsunami evacuation by blocking or damaging evacuation routes, potentially rendering them impassable, or impeding an efficient and rapid vehicular evacuation.
The objective of this report is to assist city and emergency management officials in evaluating the suitability of existing evacuation routes and assembly areas for potential susceptibility to ground failure from a M9+ CSZ earthquake. Results of this report could necessitate modifying, adding, or removing current evacuation routes and assembly areas.
The Ledgewood–Bonair Landslide (LB Landslide) on Whidbey Island, Island County, Washington occurred around 3:45 am on March 27, 2013, and is a small portion of a much larger landslide complex. The larger landslide, which is approximately 1.5 miles long, is prehistoric and may date back as much as 11,000 years. The LB Landslide is likely a reactivation of a small portion of the prehistoric complex. The dimensions of the landslide are approximately 1100 feet long (measured parallel to the shoreline) and about 300 feet into Puget Sound. Initial estimations place the volume of material mobilized as great as 200,000 cubic yards (~40,000 dump truck loads).
During the storm event of December 1–3, 2007, heavy rains and rapid snowmelt triggered thousands of landslides throughout western Washington. Landslides blocked or damaged roads, isolating communities in the height of the storm and delaying emergency response. At least one person died as a consequence of the storm.
This report presents the findings of a geotechnical investigation by the Department of Natural Resources (DNR) Division of Geology and Earth Resources (DGER) into the stability of the bluff's surrounding the Capitol Campus.
After the 1983 and 1984 debris torrents in neighboring Mills Creek, concerns were raised regarding the potential for downstream impacts in the Thunder Creek drainage. In response to these concerns, the major property owners in the watershed agreed in 1988 that an overview of the basin should be conducted. This reconnaissance was to identify the nature and areas of potential stability problems as well as downstream areas potentially subject to impacts. In addition, the overview was to assemble data useful for forest land management within the basin.
Washington is one of the most landslide-prone states in the country, with hundreds to thousands of events each year. The direct cost of landslide damage includes the repair of roads and property. Indirect costs, such as loss of property value and tax revenue, and environmental effects, such as the degradation of water quality, can exceed direct costs. The Washington Dept. of Transportation routinely budgets $15 million a year for cleanup of landslides on highways. This fact sheet is designed to provide general information about landslide hazards and possible warning signs. Individual landslides have many variables and are not predictable.
The Chimborazo Hill landslide occurred on the evening of Monday, August 30, 2004, in the wake of Tropical Depression Gaston. Although the area of the slide at the Chimborazo Park playground at 31st and Grace streets garnered much attention and remediation efforts, it was but a small section of a much larger landslide that covered approximately 11 acres on the west-facing slope of Chimborazo Hill.
The purpose of our investigation was to determine the cause of the landslide, document physical characteristics of the landslide, and evaluate the remaining landslide hazard to aid South Weber City in determining when to allow evacuated residents to return and in assessing the long-term risk to development at the base of the bluff.