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Digital terrain models of Spirit Lake blockage and Mount St. Helens debris avalanche, based on 1980-2018 airborne photogrammetry surveys

June 17, 2019

The lateral blast, debris avalanche, pyroclastic flows, and lahars of the May 18th, 1980, eruption of Mount St. Helens, Washington, dramatically altered the surrounding landscape. The debris avalanche and pyroclastic flows filled upper North Fork Toutle River valley and blocked the outlet of Spirit Lake. To mitigate the risk of a catastrophic breach, lake outflow was pumped over the blockage prior to rerouting through a 2.6-kilometer long tunnel completed in 1985 by the U.S. Army Corps of Engineers. However, periodic major repairs to the tunnel have caused responsible parties to reevaluate long-term lake outlet options. This dataset presents a time series of digital terrain models (DTM) of the Spirit Lake blockage and Mount St. Helens debris avalanche in upper North Fork Toutle River valley. Airborne photogrammetry surveys were conducted in 1980, 1981, 1982, 1984, 1985, 1996, 2015, and 2018. Structure-from-motion techniques were used to produce each DTM from each survey. This USGS data release contains digital elevation data as 1-meter resolution raster datasets (for example, dtm_YEAR.tif). These DTMs can be used to better understand sediment erosion, transport, and deposition across the blockage.

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