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

2006年11月的第一个星期，一场由副热带急流带来的强风暴在太平洋西北部上空停止，使该地区遭受了创纪录的降雨。经过六天的强降雨，俄勒冈州和华盛顿州喀斯喀特山脉的十几个冰川下面引发了大规模的泥石流。胡德山和雷尼尔山的冰川排水受到的打击尤其严重。在胡德山，在5个主要水道上记录了大量的泥石流，发生在山的每个斜坡上。在雷尼尔山更北的地方，碎屑流发生在朝北的冰川下面，比如温斯洛普冰川，以前这种碎屑流只在朝南、朝东和朝西的冰川水系上被记录下来。泥石流的数量和规模及其不同寻常的方向分布似乎表明触发机制发生了变化。我们过去关于泥石流诱因的概念正在受到挑战。应对这一挑战的第一步是绘制出这些火山周围泥石流范围的完整地图。该提案寻求获得胡德山高分辨率正射正正可见光/近红外卫星图像（“正射正像”）的资金。目前正在获取该地区的机载激光雷达数据，以便绘制泥石流的表面高程。然而，可见光/近红外正射影成像并没有计划作为激光雷达采集的一部分。卫星正射图像将提供杠杆作用，方便地显示2006年11月的泥石流的全部范围，这些泥石流尚未被绘制出来。光靠激光雷达测高技术无法区分老的和新形成的泥石流，也无法轻易区分开始带的特征，如暴露的冰川冰、岩石覆盖的冰川、冰碛和新沉积的物质。为了正确解释激光雷达测高，需要可见光/近红外图像来提供这一重要的背景信息。目前正在获取雷尼尔山的激光雷达测高数据和正校正航空照片，以检查2006年11月那里的泥石流和洪水的范围。该项目将利用QuickBird卫星图像（60厘米分辨率）与激光雷达数据进行融合。我们还建议对受影响的排水进行初步分析，并与雷尼尔山上的几次泥石流进行一些有限的比较。这是一个紧急的、时间敏感的数据问题，因为必须在季节性积雪掩盖该地区和冬季风暴进一步改变泥石流及其起始地点之前获得卫星正射影像。这项工作是朝着从地貌学和气候学的综合角度研究这些冰缘泥石流的完整提案迈出的关键的第一步。更广泛的影响除了地图、特征和对喀斯喀特冰川周围泥石流的更好理解之外，我们还将在一篇通俗科学期刊文章中传达我们的结果。我们亦会透过网站及向有关机构介绍我们的调查结果。Nolin和Lancaster将部分支持和培训一名研究生，以执行QuickBird和LiDAR数据的正校正。这项工作与正在进行的沙地河流域的研究有重要的联系，土拨鼠大坝正在被拆除。2006年11月的洪水事件显著地改变了上游的排水，并为下游提供了大量的沉积物。这个纵向剖面需要QuickBird图像来与2006年11月事件之前获得的航空照片和激光雷达进行比较。

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.