MCA: Multi-scale considerations of climatic signatures on debris flows and alluvial fans

在世界范围内，社区正在经历风暴频率和强度的历史性变化，这些风暴摧毁了房屋和生命。频繁和/或强烈风暴的最具破坏性的影响之一是，相关的降雨可以破坏泥土材料的稳定性，破坏自然和建筑基础设施的基础。在这样的条件下，这些材料可以沿斜坡向下流动，随后夹带额外的材料，并急剧增加尺寸。它们的增长速度和演变可能是惊人的，因为它们添加了泥浆，岩石，甚至是一米大小的巨石，成为巨大的泥石流河流。这些泥石流在流动时可能会突然改变方向，甚至形成自己的通道壁或堤坝，从而在相对于周围环境“超高”时保持高速。这些流动的时间，方向和规模的不可预测性可能会增加其破坏性，例如，加州蒙特西托县2018年泥石流的死亡和破坏。 为了更好地减轻灾害，科学家需要了解当地材料，湿度和当地气候条件等细节如何决定这些行为。该项目涉及使用以前的流动及其沉积物，物理实验和计算模拟的数据进行研究，以帮助我们更好地预测和预测在不同气候条件下可能的未来流动行为。该项目结合了实地工作，实验室实验，颗粒物理学理论和计算建模，以了解特定泥石流事件外部的气候条件和嵌入这些条件的流动物理学的综合影响。 这将涉及一个新的框架，涉及沉积物-流体特性和边界条件，因为它涉及到不同条件下的泥石流行为。试验工作将包括：（1）简单基础条件下的控制滑塌-泥浆实验;（2）侵蚀渠化实验;（3）冲积扇实验。计算工作将建立在嵌入多相离散元法（DEM）模型的沉积物流体流变学基础上。野外工作将包括在因其独特的气候和物理信号而选定的地点进行泥石流沉积，以帮助识别以下方面的信号：（1）理查森山脉的冰缘沉积（随着气候变化而变化的沉积物供应）与合作伙伴达特茅斯学院的玛丽莎·帕卢西斯教授;（2）台湾老农溪流域沿着较湿较暖的沉积物（高沉积物供应、潮湿条件、独特的集水区岩性）;（3）欧文斯谷较干燥、较热的沉积物中含有明显的气候和岩性差异的标志。 计划与土著社区开展的工作将通过他们的积极参与和社区记录为科学做出贡献。该奖项由地貌学和土地利用动力学计划以及颗粒和多相过程计划共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估而被认为值得支持。

Worldwide, communities are experiencing historic changes in storm frequencies and magnitudes that destroy homes and lives. One of the most devastating effects of frequent and/or intense storms is the way in which associated rainfall can destabilized earthen materials and liquefy the very foundation of natural and built infrastructure. Under such conditions, these materials can flow downslope, subsequently entrain additional materials, and increase in dramatically size. Their growth rate and evolution can be alarming as they add mud, rocks, and even meter-sized boulders to become massive rivers of debris flows. These debris flows may abruptly change direction as they flow, and even create their own channel walls, or levees, thus maintaining a high speed as they “super-elevate” relative to their surroundings. The unpredictability of the timing, directions, and magnitudes of these flows can add to their devastation as evident, for example, in the deaths and destruction of the 2018 debris flows in Montecito County, California. For better hazard mitigation scientists need to understand how details such as local materials, moisture, and local climate conditions dictate these behaviors. This project involves research using data from previous flows and their deposits, physical experiments, and computational simulations to help us better anticipate and predict behaviors of likely future flows under varying climatic conditions. This project combines field work, laboratory experiments, granular physics theory, and computational modeling to understand combined effects climate conditions external to specific debris flow events and flow physics embedded in those conditions. This will involve a new framework relating sediment-fluid specifics and boundary conditions as it relates to debris flow behaviors under varying conditions. Experimental work will include: (1) controlled slump-slurry experiments with simplistic basal conditions; (2) erosional channelized experiments, and (3) alluvial fan experiments. Computational work will build on sediment-fluid rheology embedded in a multi-phase discrete-element-method (DEM) model. Field work will include debris flow deposits at sites selected for their distinct climatic and physics-based signals to help identify signals from each: (1) on periglacial deposits in the Richardson Mountains (changing sediment supply with climate changes) with collaborative partner Professor Marisa Palucis of Dartmouth College; (2) on wetter warmer deposits along the Laonong River Valley, Taiwan (high sediment supplies, moist conditions, distinct catchment lithologies); (3) in drier hotter deposits in Owens Valley that contain signatures of distinct climate and lithology differences. Planned work with indigenous communities will contribute to the science with their active involvement and community records. This award is jointly funded by the Geomorphology and Land-use Dynamics Program and the Particulate and Multiphase Processes Program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.