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Jonathan W. Godt

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When debris flows grow by entraining sediment, they can become especially hazardous owing to increased volume, speed, and runout. To investigate the entrainment process, we conducted eight largescale experiments in the USGS debris-flow flume. In each experiment, we released a 6 m3 water-saturated debris flow across a 47-m long, ~12-cm thick bed of partially saturated sediment lining the 31º flume. Prior to release, we used low-intensity overhead sprinkling and real-time monitoring to control the bed-sediment wetness. As each debris flow descended the flume, we measured the evolution of flow thickness, basal total normal stress, basal pore-fluid pressure, and sediment scour depth. When debris flows traveled over...
Categories: Publication; Types: Citation
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This cover contains the outlines of recent landslides formed prior to Hurricane Mitch in October - November 1998. Jeffrey Coe and Robert Bucknam mapped the landslides. Most landslides were mapped using 1:40,000-scale aerial photographs and a Kern PG-2 photogrammetric plotter at 4X and 8X magnifications. The photographs were scaled and oriented to the topographic base map using prominent topographic landmarks and plotted on a transparent polyester overlay registered to the topographic base maps at scales of 1:50,000 or 1:25,000. In areas where landslides were very sparse, the aerial photographs were scanned with a mirror stereoscope at 4X magnification, and landslide locations were transferred to base maps by inspection....
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The torrential rains that accompanied Hurricane Mitch in October and November of 1998 triggered thousands of landslides in the moderate to steep terrain bordering the Motagua and Polochic Rivers in eastern Guatemala. Using aerial photographs taken between January and March 2000 we mapped all visible landslides larger than about 15 m in minimum dimension in a study area of 10,000 km2 encompassing twenty 1:50,000-scale topographic map quadrangles. Rainfall from Hurricane Mitch was exceptional because it was geographically widespread, prolonged over a period of about a week, moderate to heavy in intensity, and occurred at the end of the rainy season when the ground already had a high moisture content. As documented...
Categories: Publication; Types: Citation; Tags: Open-File Report
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This volume brings together case studies and summary papers describing the application of state-of-the-art engineering geologic methods to landslide hazard analysis for the Seattle, Washington, area. An introductory chapter provides a thorough description of the Quaternary and bedrock geology of Seattle. Nine additional chapters review the history of landslide mapping in Seattle, present case studies of individual landslides, describe the results of spatial assessments of landslide hazard, discuss hydrologic controls on landsliding, and outline an early warning system for rainfall-induced landslides.
Categories: Publication; Types: Citation
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