Experiments on debris-flow initiation from runoff

在陡峭的山地地形中，泥石流对泥沙运移和基岩河道切割起主导作用，并驱动景观变化。虽然泥石流通常是由在破坏后流化的滑坡产生的，但越来越多的证据表明，径流和坡面流产生的泥石流的重要性，特别是在陡峭的高山景观和野火之后，干燥、松散的沉积物在破坏前聚集在渠道和滑槽中。径流产生泥石流的起始机制尚不清楚。为了解决这个问题，将进行一系列实验，这些实验将构成测试和发展山间河道泥石流起生理论的基线。这些实验将在加州理工学院一个新的最先进的设施中进行，该设施专门用于研究非常陡峭的斜坡上的沉积物运输过程。拟议的工作将测试四种假设，这些假设涉及在大范围的河道坡度和沉积物大小上发生的泥石流。这项工作的预期结果是对控制河道内泥石流形成的潜在机制的新见解，以及将泥石流形成与地形（如河道坡度）和环境扰动（如洪水和野火）联系起来的预测模型的发展。泥石流是世界范围内山地地形最危险和最昂贵的灾害之一。这项工作将提高我们对泥石流起源的理解，并有助于我们预测灾害和制定更好的土地利用战略的能力。该研究结果将应用于洛杉矶地区，在那里，野火后经常发生径流产生的泥石流，导致生命和财产损失。这些结果将通过期刊出版物向公众公布，并通过旨在为年轻教育工作者提供资源的GeomorphLectures Wiki向科学教学界公布。教育和推广活动包括培训本科生、博士和博士后水平的科学家，以及通过与加利福尼亚州帕萨迪纳联合学区合作的志愿者课堂演讲和实验室参观。

In steep mountain terrain, debris flows can dominate sediment transport and bedrock channel incision, and drive landscape change. Although debris flows are often generated from landslides that fluidize upon failure, there is increasing evidence for the importance of debris flows generated from runoff and overland flow, especially in steep alpine landscapes and following wildfire where dry, loose sediment collects in channels and chutes prior to failure. The initiation mechanisms for debris-flow generation from runoff are not well understood. To address this, a series of experiments that will form the baseline to test and develop theory for debris-flow initiation in mountain channels will be conducted. The experiments will take place in a new state-of-the-art facility at the California Institute of Technology designed specifically to investigate sediment transport processes on very steep slopes. The proposed work will test four hypotheses concerning the onset of debris flows over a wide range of channel slopes and sediment sizes. The expected outcome from this work is new insight into the underlying mechanics that control debris-flow initiation from within channels, and the development of predictive models that link debris flow initiation to topography, such as channel slope, and environmental perturbations, such as floods and wildfires. Debris flows are one of the most dangerous and costly hazards of mountainous terrain worldwide. This work will improve our understanding of debris flow initiation and aid in our ability to forecast hazards and develop better land-use strategies. The results will have applications for the Los Angeles area where runoff-generated debris flows are common following wildfire, in cases resulting in loss of life and property damage. These results will be made available to the public through journal publications and to the scientific teaching community through the GeomorphLectures Wiki, designed to be a resource for young educators. Educational and outreach activities include training scientists at the undergraduate, PhD and postdoctoral levels, and volunteer classroom presentations and laboratory tours through collaborations with the Pasadena Unified School District, CA.