Sediment Storage at the Transition Between Debris-Flow and Fluvial Processes

泥石流与河流过程过渡时期泥沙淤积工程摘要概论。为了更好地了解沉积、滞留和疏散机制以及受泥石流沉积强烈影响的山谷中的沉积物收支，本研究将描述俄勒冈海岸山脉源头溪流中沉积物储存的体积、年龄和沉积学特征，以及它们与流域和当地山谷特征的关系。该项目将解决一个关键的界面，在源到汇流的沉积物的景观。现代地貌学的一个重要目标是确定控制地貌系统通量的一阶速率定律，本项目专门解决这一问题。为了在山区的开发和保护之间达成明智的妥协，了解调节偶发性干扰（如森林火灾和相关泥石流）对下游影响的自然机制至关重要。这项研究将有助于围绕太平洋西北地区和其他地方的森林实践和生境进行科学和政治辩论，阐明泥石流产生的沉积物脉冲的下游衰减，并将这些信息提供给管理人员和决策者。技术描述。山间溪流中沉积物沉积、滞留和排泄的机制、速率和体积是什么？这些机制、速率和体积在下游是如何变化的？它们之间有什么联系？它们如何受到气候变化的影响？调查将包括沿着泥石流和河流过程过渡的不同位置的河流，从泥石流冲刷和沉积都很重要的山谷，通过泥石流冲刷似乎不重要但泥石流沉积占主导地位的山谷，到支流的泥石流沉积只是打断其他河流沉积的山谷。具体的研究活动将包括：(1)用机载激光测绘（ALSM）测绘和测量整个水源网络的沉积物体积，以及地面测绘和地面测量方法的测试；(2)沉积物沉积地层学、沉积物放射性碳年龄分布、地层阶地特征和填图，阐明沉积的滞留和疏散机制、疏散时间以及气候变化引起的变化；(3)利用数字高程模型（dem）分析沉积物体积和特征以及河谷形态（如沟阶）对网络结构和地形的依赖关系。由于先前的研究提供了地貌过程和古气候方面的知识，因此实地地点将位于始新世砂岩地层（Tyee）下的俄勒冈海岸山脉（OCR）的部分地区；泥石流主导着向上游河谷的泥沙输送；第四纪气候变化未改变主导地貌过程；OCR分别是开发和保护倡导者之间争论的焦点；这个区域很容易到达。

Sediment Storage at the Transition Between Debris-Flow and Fluvial Processes Project AbstractBroad Explanation. In order to better understand deposition, retention, and evacuation mechanisms and the sediment budget in valleys strongly affected by debris-flow deposition, the proposed research will characterize volumes, ages, and sedimentology of sediment storage and their relationships to contributing drainage basin and local valley characteristics in headwater streams of the Oregon Coast Range. This project will address a key interface in the source-to-sink flow of sediment off landscapes. An important goal in modern geomorphology is to determine the first-order rate laws that govern fluxes in geomorphic systems, and this projectl specifically addresses this issue. To reach an informed compromise in mountainous areas between exploitation and conservation, it is vital to understand the natural mechanisms mediating downstream effects of episodic disturbances such as forest fires and associated debris flows. The research will contribute to the scientific and political debate around forest practices and habitat in the Pacific Northwest and elsewhere by elucidating the downstream attenuation of debris-flow-derived sediment pulses and presenting that information to managers and policy-makers. Technical Description. What are the mechanisms, rates, and volumes of sediment deposition, retention, and evacuation in mountain streams, and how do these mechanisms, rates, and volumes change downstream? How are they related? How are they affected by climate change? Investigations will encompass streams at varying positions along the transition between debris-flow and fluvial processes, from valleys where both debris-flow scour and deposition are important, through valleys where debris-flow scour appears unimportant but debris-flow deposits predominate, to valleys where debris-flow deposition from tributaries merely punctuates otherwise fluvial deposits. Specific research activities will include (1) mapping and measurement of sediment volumes throughout headwater networks with airborne laser swath mapping (ALSM) and ground-based mapping and testing of the method with ground-based surveying; (2) characterization and mapping of deposit sedimentology and stratigraphy, deposit radiocarbon age distributions, and strath terraces to elucidate retention and evacuation mechanisms, evacuation times, and changes due to climate change; and (3) analysis of digital elevation models (DEMs) to find the dependence of deposit volumes and characteristics and valley morphology (e.g., strath terraces) on network structure and topography.Field sites will be in parts of the Oregon Coast Range (OCR) underlain by an Eocene sandstone formation (Tyee) because prior studies provide knowledge of geomorphic processes and paleoclimate; debris flows dominate sediment delivery to storage in headwater valleys; Quaternary climate change has not changed the dominant geomorphic processes; the OCR is the focus of debate between advocates of exploitation and conservation, respectively; and this area is readily accessible.