Hydrologic conditions and terrestrial laser scanning of post-fire debris flows in the San Gabriel Mountains, CA, U.S.A.
Hydrologic conditions and terrestrial laser scanning of post-fire debris flows in the San Gabriel Mountains, CA, U.S.A.
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美国加利福尼亚州圣盖博山脉火灾后泥石流的水文状况和地面激光扫描
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发表时间：
2011
期刊：
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通讯作者：
G. Bawden
中科院分区：
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作者：
K. Schmidt;M. N. Hanshaw;J. Howle;J. Kean;D. Staley;J. Stock;G. Bawden
为了调查产生野火后泥石流的降雨径流条件，我们对加利福尼亚州圣加布里埃尔山脉活跃前沿陡峭的小流域进行了测量和调查。幸运的是，我们记录到了由一次空间受限对流事件引发的径流产生的泥石流，降雨量为28毫米，降雨量超过62分钟。我们的雨量计、嵌套的山坡陆地流量传感器和土壤湿度探测器，以及陆地激光扫描(TLS)的时间序列，揭示了风暴的影响。沿垂直于排水分水岭和源自排水分水岭的两条长约10米的流线的山坡坡面径流响应，显示出距离降雨只有10-20分钟的延迟，累积总降雨量仅为5-10毫米。深度分层土壤水分探头显示出较大的时间延迟，约为20-30分钟，表明初始陆面流是霍顿式的。此外，下游河道监测阵列记录了18分钟降雨后泥石流通过所产生的显著流量峰值。此时，11个山坡坡面流量传感器中只有4个确认了地表水流动的存在。重复TLS和使用GPS的详细野外测绘记录了雨溅、陆流冲刷和细沟模式如何促成中尺度泥石流的产生。为响应一场小风暴，泥石流在山坡上沉积了不规则的堤坝和分叶状的末端口鼻，造成了大范围的泥石流。
To investigate rainfall-runoff conditions that generate post-wildfire debris flows, we instrumented and surveyed steep, small watersheds along the tec- tonically active front of the San Gabriel Mountains, California. Fortuitously, we recorded runoff-generat- ed debris-flows triggered by one spatially restricted convective event with 28 mm of rainfall falling over 62 minutes. Our rain gages, nested hillslope over- land-flow sensors and soil-moisture probes, as well as a time series of terrestrial laser scanning (TLS) revealed the effects of the storm. Hillslope overland- flow response, along two ~10-m long flow lines per - pendicular to and originating from a drainage divide, displayed only a 10 to 20 minute delay from the on- set of rainfall with accumulated totals of merely 5-10 mm. Depth-stratified soil-moisture probes displayed a greater time delay, roughly 20- 30 minutes, indicating that initial overland flow was Hortonian. Furthermore, a downstream channel-monitoring array recorded a pronounced discharge peak generated by the passage of a debris flow after 18 minutes of rainfall. At this time, only four of the eleven hillslope overlandflow sensors confirmed the presence of surface-water flow. Repeat TLS and detailed field mapping using GPS document how patterns of rainsplash, overland-flow scour, and rilling contributed to the generation of me- ter-scale debris flows. In response to a single small storm, the debris flows deposited irregular levees and lobate terminal snouts on hillslopes and caused wide-