Landsliding and the Evolution of Mountainous Landscapes

滑坡和山地景观的演变

• 批准号: 0447190
• 负责人: Joshua Roering
• 金额: $ 15.4万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-15 至 2008-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0447190&HistoricalAwards=false
• 关键词: Landsliding; Evolution; Mountainous; Landscapes

ABSTRACTLandsliding is the dominant erosional mechanism in most mountainous landscapes. We have a poor understanding of how factors such as climatic and tectonic forcing, channel network characteristics and bedrock properties govern the spatial and temporal pattern of hillslope adjustment; upland regions are predominantly erosional in nature and thus do not retain a direct 'record' of process dynamics. Furthermore, no quantitative models exist to predict the dynamics of large landslides over geomorphic timescales. As a result, fundamental questions regarding the role of landslides in landscape evolution remain: o How long do large landslides persist in the landscape? What controls their long-term activity? o How do large landslides affect topographic development and sediment production? o How does landslide-driven sediment production affect channel morphology and valley incision? The objective of this proposal is to quantify the effects of landsliding on sediment production and hillslope morphology by quantifying spatial and temporal patterns of slope instability in a landslide-dominated catchment. The upper Redwood Creek drainage basin (~200 km2), California, is an ideal laboratory for this endeavor because: over 80% of the catchment is comprised of landslide-prone terrain, the region experiences high rates of rock uplift, and extensive studies have documented geomorphic process rates and deformation associated with slow, intermittent earthflows and slumps using photogrammetric and field-based methods. Although several slope failures in Redwood Creek exhibit significant historical activity, ubiquitous dormant landslides (i.e., hummocky hillslopes) with varying degrees of degradation are the legacy of prior phases of widespread slope instability. Using high-resolution topographic data generated via airborne laser swath mapping (ALSM), we propose to document how tectonic and climatic forcing affect the long-term pattern of slope instability in Redwood Creek by quantifying the detailed morphology of landslide-prone hillslopes. The style and relative age of landsliding can be constrained via statistical analyses of terrain roughness; meter-scale scarps, debris levees, and folds are fresh and well defined in recent failures and become increasingly subdued and smooth on older landslides. We will calibrate quantitative measures of terrain roughness with estimates for the timing of slide activity (established via radiometric dating of undrained depressions) to document the chronology and style of slope deformation across the study area. When coupled with studies of valley dynamics, paleoclimate, and paleoseismicity, our analysis will permit us to test hypotheses relating the history and pattern of slope instability with various external perturbations. Broader Impacts The proposed research has significant implications for earth scientists seeking to understand mountain-scale denudation, land-use impacts, and the effect of climate change on surficial processes. Because landslide-derived sediment production profoundly affects grain size and channel properties, our catchment-wide analysis of slope instability will be useful for establishing linkages between hillslope processes and aquatic habitat. In Redwood Creek, zones of focused historical erosion related to land-use practices (such as gullys, earthflows, and shallow landslides) are systematically superimposed on hillslopes shaped by a complex mosaic of large landslides. Our analyses will enable land managers to better predict and remediate impacts of timber harvesting and climate change. The ALSM dataset will also serve as a baseline for characterizing future hillslope and channel system dynamics. On a broader scale, the results will serve to excite simulations of sediment routing, dispersal, and deposition across continental margins, establishing direct linkages between sediment production and marine deposits. The research will be strengthened through direct collaboration with federal and state land management agencies.

摘要滑坡是大多数山地景观的主要侵蚀机制。我们有一个贫穷的了解，如气候和构造强迫，通道网络特性和基岩特性的因素，治理的空间和时间模式的山坡调整;高地地区主要是侵蚀的性质，因此不保留一个直接的“记录”的过程动态。此外，还没有定量模型来预测地貌时间尺度上的大型滑坡的动态。因此，关于滑坡在景观演变中的作用的基本问题仍然存在：o大型滑坡在景观中持续多久？是什么控制了他们的长期活动？o大型滑坡如何影响地形发展和沉积物产生？滑坡驱动的沉积物产生如何影响河道形态和河谷下切？本提案的目的是通过量化滑坡为主的集水区的边坡不稳定性的空间和时间模式来量化滑坡对泥沙产生和山坡形态的影响。位于加州的红木溪上游流域（约200平方公里）是这一奋进的理想实验室，因为：超过80%的流域由易滑坡地形组成，该地区经历了高速率的岩石隆起，并且广泛的研究已经使用摄影测量和基于实地的方法记录了与缓慢、间歇性的泥石流和滑塌相关的地貌过程速率和变形。虽然红木溪的几个边坡破坏表现出重大的历史活动，无处不在的休眠滑坡（即，这些斜坡（包括丘状山坡）的退化程度各不相同，都是先前斜坡普遍不稳定阶段的遗留问题。使用高分辨率的地形数据，通过机载激光测绘（ALSM），我们建议记录构造和气候强迫如何影响长期模式的斜坡不稳定性红木溪量化的详细形态滑坡倾向的山坡。滑坡的类型和相对年龄可以通过地形粗糙度的统计分析来限制;米级陡坎、碎屑堤和褶皱在最近的失败中是新鲜的，并且在较老的滑坡中变得越来越柔和和平滑。我们将校准地形粗糙度的定量测量，估计滑坡活动的时间（通过不排水洼地的放射性测年建立），以记录整个研究区域的边坡变形的年表和风格。再加上山谷动力学，古气候和古地震活动的研究，我们的分析将使我们能够测试有关的历史和模式的斜坡不稳定与各种外部扰动的假设。更广泛的影响拟议中的研究对地球科学家寻求了解山区规模的剥蚀，土地利用的影响，以及气候变化对地表过程的影响具有重要意义。由于滑坡产生的沉积物深刻地影响粒度和通道特性，我们的流域范围内的斜坡不稳定性分析将是有用的建立山坡过程和水生栖息地之间的联系。在红木溪，与土地利用实践（如冲沟，泥石流和浅层滑坡）相关的集中历史侵蚀区系统地叠加在由大型滑坡复杂镶嵌形成的山坡上。我们的分析将使土地管理者能够更好地预测和补救木材采伐和气候变化的影响。ALSM数据集还将作为表征未来山坡和河道系统动态的基线。在更广泛的范围内，研究结果将有助于激发对沉积物在大陆边的流动、扩散和沉积的模拟，建立沉积物产生和海洋沉积之间的直接联系。将通过与联邦和州土地管理机构的直接合作加强研究。