Small debris flows observed in the White River drainage on Mount Hood.
USGS-Cascades Volcano Observatory geologists working in the area on August 21 observed higher sediment-laden stream flows and broad areas adjacent to channels that had recently been inundated by mud and gravel.
Seismic monitoring equipment on Mount Hood detected small debris flows on the White River over the past several weeks. No significant damage has been reported, but it may have made the Timberline Trail crossing over the White River temporarily more difficult.
The seismic signals of the debris flow rumbling down channel were best recorded by monitoring station PALM, located next to the Palmer chairlift in the Timberline Ski Area. Although the station has a lot of cultural noise, especially during chair lift operations, the debris flow signals are clearly visible. The signals in the spectrograms have gradual onsets, relatively high frequency content (5-10 Hz), and extended durations.
Small debris-flow events are not uncommon in the upper reaches of the White River, particularly during periods of extended warm weather or intense rainfall. In this case, meltwater apparently released from the terminus of the White River Glacier, mixed with loose sediment as it traveled down steep narrow channels to create debris flows.
As a reminder to visitors in the area, if you are in a narrow river channel and you feel ground shaking, hear prolonged rumbling, or see a rapidly rising river level, move to the safety of higher ground.
Visit the Mount Hood National Forest for current conditions. Follow the link for more about Mount Hood.
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