OSO mudslide washington

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  • Oso mudslide, Washington State, USA March 2014
    • Why?
      • Human
        • Urbanisation
        • Highway 530 constructed beneath cliff
      • Physical
        • Elevated terrain (600ft)
        • made of silt and clay, which when wet are slippery
        • Top layer porous, so water seeps in and soaks the ground
        • Prolonged heavy rain- increased ground water pressure
        • Wettest March in history: 2ft rain in a month
        • Traveled at 40mph
    • When?
      • 10:37 am PDT on Saturday, March 22, 2014
    • Where?
      • Northwest Washington------> Oso
      • Took place along the edge of a plateau about 600 feet high composed of glacial sediments
    • What?
      • Landslide with a volume of the slide is estimated to be about 10 million cubic yards
      • Traveled about 0.7 miles from the toe of the slope.
      • Flow also dammed and temporarily blocked the upper part of the North Fork Stillaguamish River
    • Impacts
      • Economic
        • Blocked highway 530
        • Emergency services came to 4.5 million pounds
        • Total cost=10 million
        • Buried mile stretch of highway, taking 6 months to rebuild
      • Social
        • 49 homes picked up and destroyed
        • Debri from houses
        • Children Orphanised
        • People submerged in mud
      • Environmental
        • Trees pulled up from roots
        • Dammed the river
        • 1 square mile of valley buried under 50 km of mud
        • Flooding from the pool of water formed from the dam, blocking the 2.5 square mile stillaguamish
      • (Short Term)
      • (Long Term)
      • Management strategies
        • Short-term (emergency and rescue)
          • Trained air rescuers
          • Helicopter rescue team first on the scene to scan for survivors (thermal camera)
        • Long-term (Planning and Management)
          • LIDAR (lasers) can penetrate though the canopy, ad collect info about past landslides
            • take a laser in plane and shine it down on topography and measure the time it takes to get back to the instrument
          • Initial surveying from a distance
          • Carbon rock dating
          • Aerial and satellite images
          • Experiments on water retainment
          • USGS installed three rapid Deployment Gages
            • Measure additional water levels and streamflow
            • Monitor rate of erosion of dam
          • Downstream
          • USGS got three "spiders" (powerful GPS units) to detect landslide movement with vibrations.

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