--> Abstract: Slope Stability along Incised Fluvial Valleys; #90063 (2007)

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Slope Stability along Incised Fluvial Valleys

 

Morris, Alan P.1, David A. Ferrill1, Ronald N. McGinnis1, Ben A. Abbott2 (1) Southwest Research Institute®, San Antonio, TX (2) Southwest Research Institute®, San Antonio,

 

The Snake River and its tributaries in southern Idaho have incised valleys through Tertiary basalt into underlying clay-rich sediment. Incision has destabilized valley walls causing landslides. The valleys are analogous to lowstand channels cut through competent strata into less competent strata. Salmon Falls Creek, a tributary of the Snake River, flows through a relatively narrow canyon (~130 m deep, ~375 m wide). Ten kilometers south of its confluence with the Snake River, landslides originating from the canyon wall widen the canyon to 1.3 km. Several landslides have periodically dammed the creek. The most recent slide (1998, Bluegill Lake or Salmon Falls slide) is still active, and previous workers interpret it as a rotational slide detaching within sediments beneath the plateau-capping basalt. Bluegill Lake slide consists of a vertical headscarp; zones of large, precariously stacked boulders, and rotated, intact basalt pavements; a toe consisting of boulders, clay-rich strata, and fluvial sediments; and a northern strike-slip boundary. Landslides and their associated slope processes are important analogs for evaluating hydrocarbon potential of subaerial and submarine landslide deposits. We use a new high-resolution wireless sensor and node-based, displacement-monitoring network and detailed mapping, together with techniques of cross-section construction, to measure displacements and infer the internal structure of the slide. Failure mechanics within a strong capping layer above a weaker substrate are common to a number of environments including continental margin gas hydrate accumulations and lowstand systems of any age. Our new high-resolution displacement-monitoring network has wide applications to natural and anthropogenic earth surface processes.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California