Small Grant for Exploratory Research: Mapping the November 2006 Periglacial Debris Flows on Mount Hood and Mount Rainier

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During the first week of November 2006, a powerful storm borne on the subtropical jet stream stalled over the Pacific Northwest inundating the region with record amounts of rainfall. After six days of intense rainfall, major debris flows were triggered below more than a dozen glaciers in the Cascade Range of Oregon and Washington. Especially hard hit were glacier drainages on Mt. Hood and Mt. Rainier. On Mt. Hood, large debris flows were recorded on five major drainages, occurring on every slope aspect of the mountain. Further north on Mt. Rainier, debris flows occurred below north-facing glaciers such as the Winthrop Glacier, where previously such debris flows had only been documented on south, east, and west-facing glacier drainages. The number and size of the debris flows combined with their unusual aspect distribution appear to indicate a change in the triggering mechanisms. Our past conceptions of debris flow triggers are being challenged. The first step in addressing this challenge is a complete mapping of the extent of the debris flows around these volcanoes.This proposal seeks funding to acquire high-resolution orthorectified visible/near-infrared satellite imagery (?orthoimagery?) over Mt. Hood. Airborne LiDAR data are currently being acquired over the region for the purpose of mapping surface elevations of the debris flows. However, visible/near-infrared orthoimagery was not planned as part of that LiDAR acquisition. The satellite orthoimagery will provide the leverage to readily show the full extent of the November 2006 debris flows, which have not yet been mapped. LiDAR altimetry alone is not able to distinguish between old and recent debris flows neither can it easily distinguish between features in the initiation zones such as exposed glacial ice, rock-covered glaciers, moraines and newly deposited material. Visible/near-infrared imagery is needed to provide this important contextual information for correct interpretation of LiDAR altimetry. LiDAR altimetry data and orthorectified aerial photos are currently being acquired over Mt. Rainier to examine the extent of the November 2006 debris flows and floods there.This proposed project will QuickBird satellite imagery (60 cm resolution) over Mt. Hood for fusion with the LiDAR data. We also propose to perform preliminary analyses of affected drainages and perform some limited comparisons with several debris flows on Mt. Rainier. This is an urgent, time-sensitive data issue since the satellite orthoimagery must be acquired before seasonal snowcover masks the area and winter storms further modify the debris flows and their initiation sites. This work is a key first step towards developing a full proposal that will examine these periglacial debris flows from the combined perspectives of geomorphology and climatology.Broader ImpactsIn addition to the maps, characterizations, and improved understanding of these Cascadian periglacial debris flows, we will convey our results in a popular science journal article. We will also present our findings through a website and to concerned agencies. Nolin and Lancaster will partially support and train a graduate student to perform the orthorectification of the QuickBird and LiDAR data. This work has important linkages to ongoing research in the Sandy River watershed where the Marmot Dam is being removed. The November 2006 flood event significantly modified the upper portions of the drainage and provided large amounts of sediment downstream. The QuickBird imagery is needed for this longitudinal section to compare with previous aerial photos and LiDAR that were acquired prior to the November 2006 events.