Scott Burns, engineering geologist and geomorphologist and media personality was recognized by the American Geosciences Institute (AGI) with its Outstanding Contribution to the Understanding of Geoscience award. His award was presented at a ceremony at the Geological Society of America Annual Meeting hosted in Baltimore, Maryland.
On July 12, 2008 remnant moisture from hurricane Bertha moved from the Gulf of Mexico across the southwestern United States bringing tropical moisture to the Eastern Sierra Nevada. Rainfall intensities reportedly as high as 97 mm/hr (3.8 in/hr) occurred for a period of 39 minutes on the Oak Creek drainage north of Independence, in Inyo County, California. This area had been burned during the Inyo Complex fire of July 6, 2007. The storm generated debris and hyperconcentrated flows ran out 6 to 7 km (~3.8 to 4.4 mi) from the mountain front, reportedly damaging or destroying 50 residential structures, severely damaging the historic Mt. Whitney Fish Hatchery, and disrupting traffic on State Highway 395 for nearly a week. Although slopes were extensively rilled, most of the estimated 1.5 million cubic meters (~2.0 million yd3) of transported sediment was scoured from channels and deposited over an area of more than 3 km2, mostly on younger alluvial fans. Surges moved down the North Fork of Oak Creek at estimated velocities of 2 m/sec (~4.5 mi/hr) to 5.4 m/sec (~12 mi/hr) and were one to three meters high. Sand-rich, hyperconcentrated flows followed the active channel of the North Fork of Oak Creek and filled the channel where it debouched on the alluvial fan surface, spreading sediment and debris laterally across the distributary fan interfluves. Several avulsions occurred as the result of either channel plugging and flow redirection, or as channel overflow. On the South Fork of Oak Creek, boulderrich debris flows clogged the active channel, and created a boulder field of at least 1,500 m (4,600 ft) long and 75 m (230 ft) wide on the upper portion of the young alluvial fan surface. The channel of the South Fork was forced to a new course to the west. Boulders ranging from less than one meter to over three meters across, weighing up to ~26,000 kg (~57,000 lbs) were moved by the flows. Flooding and debris deposition occurred within the active stream channels and on significant portions of the young alluvial fan surfaces; older alluvial fan surfaces were unaffected, supporting the hypothesis that younger fan surfaces are the ones most likely to be affected by post-fire debris and hyperconcentrated flows.
In the first half of the 20th century, engineering geology and geotechnical engineering were in their infancy, and dams were often built where landslides provided valley constrictions, often without expert site investigation. Only the most important projects were subjected to careful geologic examination. Thus, dams were often built without complete understanding of the possible geotechnical problems occurring in foundations or abutments. Most of these dams still exist, although many have undergone costly repairs because of stability or leakage problems. Today, however, every effort is made in the selection of damsites, including those sited on landslides, to provide foundations and abutments that are generally impervious and capable of withstanding the stresses imposed by the proposed dam and reservoir, and possible landslides.
Communities in lowlands near volcanoes are vulnerable to significant volcanic flow hazards in addition to those associated directly with eruptions. The largest such risk is from debris flows beginning as volcanic landslides, with the potential to travel over 100 kilometers. Stratovolcanic edifices commonly are hydrothermal aquifers composed of unstable, altered rock forming steep slopes at high altitudes, and the terrain surrounding them is commonly mantled by readily mobilized, weathered airfall and ashflow deposits. We propose that volcano hazard assessments integrate the potential for unanticipated debris flows with, at active volcanoes, the greater but more predictable potential of magmatically triggered flows. This proposal reinforces the already powerful arguments for minimizing populations in potential flow pathways below both active and selected inactive volcanoes. It also addresses the potential for volcano flank collapse to occur with instability early in a magmatic episode, as well as the 'false-alarm problem'-the difficulty in evacuating the potential paths of these large mobile flows.