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

泥石流和河流过程过渡阶段的泥沙储存项目摘要宽泛的解释。为了更好地了解受泥石流沉积强烈影响的山谷中的沉积、滞留和排泄机制以及泥沙收支，拟议的研究将表征泥沙储存的体积、年龄和沉积学，以及它们与贡献俄勒冈海岸山脉源头溪流的流域和当地山谷特征的关系。该项目将解决景观外沉积物从源到汇流动中的一个关键界面。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级速率定律，本项目专门研究这一问题。要在山区在开发和保护之间达成知情妥协，至关重要的是要了解森林火灾和相关泥石流等间歇性干扰的下游影响的自然机制。这项研究将通过阐明泥石流引起的沉积物脉冲在下游的衰减并向管理人员和政策制定者提供信息，推动围绕太平洋西北和其他地区森林做法和栖息地的科学和政治辩论。技术说明。山区河流中泥沙沉积、滞留和排出的机制、速率和体积是什么？这些机制、速率和体积是如何在下游发生变化的？它们之间有什么关系？它们是如何受到气候变化影响的？调查将涵盖泥石流和河流过程过渡沿线不同位置的河流，从泥石流冲刷和沉积都很重要的山谷，到泥石流冲刷看似不重要但泥石流沉积占主导地位的山谷，到支流泥石流沉积只是点缀其他河流沉积的山谷。具体的研究活动将包括：(1)用机载激光条带测绘(ALSM)绘制和测量整个水源网络的沉淀量，并用地面测量对该方法进行测绘和测试；(2)沉积沉积学和地层学、沉积放射性碳年龄分布和层状阶地的表征和测绘，以阐明保留和疏散机制、疏散时间以及气候变化引起的变化；以及(3)数字高程模型(DEM)的分析，以找出沉积量和特征以及山谷形态(例如，层状梯田)与网络结构和地形的依赖关系。野外地点将位于俄勒冈州海岸山脉(OCR)的部分地区，该地区被始新世砂岩地层(TYE)覆盖，因为先前的研究提供了地貌过程和古气候的知识；泥石流主导着泥石流向源头山谷储存的泥沙输送；第四纪气候变化没有改变主导的地貌过程；OCR分别是开发和保护倡导者争论的焦点；而且这一地区很容易进入。

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.