Initiation and runout characteristics of debris flow surges in Ohya landslide scar, Japan
Initiation and runout characteristics of debris flow surges in Ohya landslide scar, Japan
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DOI：
10.1016/j.geomorph.2019.04.026
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发表时间：
2019-08
期刊：
影响因子：
3.9
通讯作者：
F. Imaizumi;T. Masui;Yushi Yokota;H. Tsunetaka;Y. Hayakawa;N. Hotta
中科院分区：
文献类型：
--
作者：
F. Imaizumi;T. Masui;Yushi Yokota;H. Tsunetaka;Y. Hayakawa;N. Hotta
泥石流的特征（例如，流速、流量、动能）高度依赖于引起水流高度、流速和漂石浓度突变的涌浪。因此，了解的启动和运行的特点，浪涌是至关重要的规划时，泥石流减灾。在日本中部的Ohya滑坡中使用10台延时相机（TLC）进行监测，由于存储的移动（即，堆积锥和通道沉积物），使我们能够获得一系列浪涌过程的数据，从开始到结束，这发生在每个泥石流事件。我们还分析了时间变化的空间分布的存储在泥石流起始区，与沉积物供应从山坡和沉积物的发生泥石流疏散，通过定期测量的地形，使用无人机（UAV）。泥石流主要是由坡面流对河道沉积物的侵蚀、河道沉积物的滑动以及河道和支流的泥沙和水补给引起的。在Ohya滑坡中，流面上自发波的发展不是涌浪形成的重要过程。当最大10 min降雨强度超过5 mm时，许多泥石流涌浪发生在与支流交汇处以下<30 m的深储存（深度>2 m）的沟段。部分饱和流，其中有一个非饱和层在其上部，是主要的流动类型在陡峭的启动区，而完全饱和流是占主导地位的温和的运输和沉积区。随着涌浪的下降，水流类型也发生了变化。当起始区中的存储体积较大时，部分饱和流占主导地位，而当存储体积较小时，完全饱和流占主导地位。当我们比较泥石流与类似的总泥沙量，旅行距离长时，完全饱和流与高流动性占主导地位，因为小体积的存储在起始区。蓄水量还通过控制涌波的流动性影响泥石流扇上的流路撕脱。因此，蓄水的空间分布和总体积是控制涌波起始位置、主导流型和终止位置的重要因素。
The characteristics of debris flows (e.g., velocity, discharge, kinematic energy) are highly dependent on surges incurring abrupt changes to flow height, velocity, and boulder concentration. Therefore, understanding the initiation and runout characteristics of surges is essential when planning debris flow mitigation. Monitoring performed using 10 time-lapse cameras (TLCs) in Ohya landslide, central Japan, where debris flows occur frequently due to mobilization of storage (i.e., talus cone and channel deposits), allowed us to obtain data on a series of surge processes, from initiation to termination, which occurred during each debris flow event. We also analyzed temporal changes in the spatial distribution of storage in the debris flow initiation zone, associated with sediment supply from hillslopes and evacuation of sediment by the occurrence of debris flows, through periodic measurements of topography using unmanned aerial vehicles (UAVs). Debris flow surges were mainly induced by repetitive mass movement of storage through the erosion of channel deposits by overland flow, sliding of channel deposits, and sediment and water supply from channel banks and tributaries. Development of a spontaneous wave on the flow surface was not an important formation process of surges in the Ohya landslide. Many debris flow surges initiated at channel sections with deep storage (>2 m in depth), located <30 m below a junction with a tributary, when the maximum 10-min rainfall intensity exceeded 5 mm. Partly saturated flow, which has an unsaturated layer in its upper part, was the predominant flow type in the steep initiation zone, while fully saturated flow was predominant in the gentle transportation and deposition zones. Flow type often changed as the surges descended. Partly saturated flow was predominant when the volume of storage in the initiation zone was large, whereas fully saturated flow was predominant when the volume of storage was small. When we compared debris flows with similar total sediment volume, travel distance was long when fully saturated flow with high flow mobility was predominant because of the small volume of storage in the initiation zone. The volume of storage also affected flow path avulsion on the debris flow fan by controlling the flow mobility of surges. Consequently, the spatial distribution and total volume of storage are important factors controlling the initiation location, predominant flow type, and termination location of surges.