Experiments on debris-flow initiation from runoff

在陡峭的山区，泥石流可以主导泥沙运移和基岩河道切割，并驱动地貌变化。虽然泥石流通常是由山体滑坡产生的，并在崩塌时液化，但越来越多的证据表明，径流和陆上流动产生的泥石流的重要性，特别是在陡峭的高山地貌和山火之后，在山体破裂之前，干燥、松散的沉积物聚集在渠道和溜槽中。从径流产生泥石流的启动机制还不是很清楚。为了解决这一问题，将进行一系列实验，这些实验将成为检验和发展山区河道泥石流引发理论的基线。这些实验将在加州理工学院的一个新的最先进的设施中进行，该设施专门为研究非常陡峭的斜坡上的泥沙输送过程而设计。这项拟议的工作将检验关于泥石流在广泛的河道坡度和沉积物大小范围内开始的四个假设。这项工作的预期成果是对从渠道内部控制泥石流引发的基本机制有了新的见解，并开发出将泥石流引发与地形(如渠道坡度)和环境扰动(如洪水和野火)联系起来的预测模型。泥石流是全世界山区最危险和代价最高的灾害之一。这项工作将提高我们对泥石流引发的了解，并有助于我们预测危险和制定更好的土地利用战略。结果将适用于洛杉矶地区，那里在野火后径流产生的泥石流很常见，在导致生命损失和财产损失的情况下。这些成果将通过期刊出版物向公众公布，并通过地貌讲座维基向科学教学界公布，该维基是为青年教育工作者设计的资源。教育和外展活动包括培训本科生、博士和博士后级别的科学家，并通过与加利福尼亚州帕萨迪纳联合学区的合作，进行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.