Evaluating Factors for Controlling Sediment Connectivity of Landslide Materials: A Flume Experiment
Evaluating Factors for Controlling Sediment Connectivity of Landslide Materials: A Flume Experiment
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DOI：
10.3390/w11010017
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发表时间：
2018-12
期刊：
影响因子：
3.4
通讯作者：
H. S. Kharismalatri;Y. Ishikawa;T. Gomi;R. Sidle;K. Shiraki
中科院分区：
文献类型：
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作者：
H. S. Kharismalatri;Y. Ishikawa;T. Gomi;R. Sidle;K. Shiraki
滑坡沉积物到河流系统和河流系统内的连通性是影响山坡物质动员程度的一个关键因素。特别是，滑坡堤坝的形成和向滑坡引发的泥石流的转化是滑坡泥沙运动的“末端成员”。为了量化沉积物的连通性，我们开发了一个代表支流和主河道的两段水槽。泥沙的流动性由多种地形因素组合而成，如支流入流角(0~90°，增量为30°)和主河道坡度(10°和15°)，以及泥沙含水率(0~100%，增量为20%)。我们还考察了来自不同岩性(砂岩和页岩、火山碎屑沉积、风化花岗岩和风化沉积岩)的沉积物之间的流动性差异。沉积物的流动性因沉积物的含水率不同而不同，特别是小于饱和或大于饱和。当所有类型的非饱和滑坡泥沙以60°和90°的入流角度进入航道时，都发生了大量的淤积，表明滑坡坝的形成。在陡峭河道(15°)的小来流角(0°和30°)下，50%的滑坡泥沙被运往下游，表明发生了泥石流。火山碎屑岩沉积在结合角的沉积量较大，其次是风化花岗岩、风化沉积岩，最后是砂页岩。我们的连通性指数表明，滑坡坝的形成和泥石流的发生之间存在一个阈值，与地形条件、含水率和沉积物类型有关。
Connectivity of landslide sediment to and within fluvial systems is a key factor affecting the extent of mobilization of hillslope material. In particular, the formation of landslide dams and the transformation into landslide-induced debris flows represent “end members” of landslide sediment mobility. To quantify sediment connectivity, we developed a two-segment flume representing tributary inflow and the main channel. Mobility of sediment was examined by combinations of various topographic factors, such as tributary inflow angle (0 to 90° in 30° increments) and main channel gradient (10° and 15°), as well as water content of sediment (0 to 100% in 20% increments). We also examined differences of mobility among sediments derived from various lithologies (sand and shale, pyroclastic sediment, weathered granite, and weathered sedimentary rock). Mobility of sediment differed, depending on the water content of sediment, particularly less than saturation or greater than saturation. When all types of unsaturated landslide sediments entered the channel at inflow angles of 60° and 90°, substantial deposition occurred, suggesting the formation of landslide dams. At low inflow angles (0° and 30°) in a steep channel (15°), >50% of landslide sediment was transported downstream, indicating the occurrence of a debris flow. The amount of sediment deposited at the junction angle was greater for pyroclastic sediment followed by weathered granite, weathered sedimentary rock, and finally, sand and shale. Our connectivity index suggests that a threshold exists between landslide dam formation and debris flow occurrence associated with topographic conditions, water content, and types of sediment.