Storm rainfall conditions for floods and debris flows from recently burned areas in southwestern Colorado and southern California
Storm rainfall conditions for floods and debris flows from recently burned areas in southwestern Colorado and southern California
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DOI：
10.1016/j.geomorph.2007.03.019
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发表时间：
2008-04-15
期刊：
影响因子：
3.9
通讯作者：
Laber, Jayme L.
中科院分区：
文献类型：
--
作者：
Cannon, Susan H.;Gartner, Joseph E.;Laber, Jayme L.
在最近烧毁的地区暴雨期间产生的泥石流摧毁了整个美国西部的生命和财产现场证据表明，不像滑坡引发的泥石流，这些事件没有可识别的启动源，可以发生很少或根本没有先前的水分。使用雨量计和响应数据从五个火灾在科罗拉多和南部加州，我们记录的降雨条件，引发火灾后泥石流和经验降雨强度持续时间阈值的发生泥石流和洪水后，在这些设置。这些信息可以为预警系统提供指导，并在类似的settings.Debris流的应急响应计划，从25个最近烧毁的盆地在科罗拉多在响应13个短持续时间，高强度的对流风暴。泥石流是在短短6到10分钟的暴雨后引发的。大约80%的泥石流风暴持续时间不到3小时，大部分降雨时间不到1小时。引发泥石流的风暴的平均强度在1.0和32.0 nun/h之间，重现间隔为两年或更短。洪水和泥石流的阈值降雨条件足以对科罗拉多中南部和西南部最近烧毁的地区的生命和财产构成威胁，其定义如下：I=6.5D（-0.7）和I=9.5D（-0.7），其中I=降雨强度（mm/h），D=持续时间（h）。泥石流是由加州南部68个最近被烧毁的地区对长时间锋面风暴的响应而产生的。在低强度（2-10毫米/小时）降雨后，水流发生了短至两小时，长至16小时。风暴持续时间为5.5至33小时，平均强度为1.3至20.4毫米/小时，重现间隔为两年或更短。文图拉县和圣贝纳迪诺火灾后第一个冬季期间威胁生命和财产的洪水和泥石流的阈值降雨条件，加州南部的圣盖博山和圣哈辛托山分别定义为I=12.5D（-0.4）和I=7.2D（-0.4）。I-14.0D的圣贝纳迪诺、圣盖博和圣哈辛托山脉经过一年的植被恢复和沉积物清除后，洪水和泥石流条件的阈值（-0.5）比火灾后第一年的发展速度高出约25 mm/h。这里定义的阈值明显低于大多数未燃烧环境的阈值，这也许是因为在燃烧过的地区以径流为主的极其迅速的过程与在未燃烧过的山坡上以渗透为主的较长期过程之间的差异。皇冠版权所有（C）2007年出版的爱思唯尔B. V.保留所有权利。
Debris flows generated during rain storms on recently burned areas have destroyed lives and property throughout the Western U.S. Field evidence indicate that unlike landslide-triggered debris flows, these events have no identifiable initiation source and can occur with little or no antecedent moisture. Using rain gage and response data from five fires in Colorado and southern California, we document the rainfall conditions that have triggered post-fire debris flows and develop empirical rainfall intensity-duration thresholds for the occurrence of debris flows and floods following wildfires in these settings. This information can provide guidance for warning systems and planning for emergency response in similar settings.Debris flows were produced from 25 recently burned basins in Colorado in response to 13 short-duration, high-intensity convective storms. Debris flows were triggered after as little as six to 10 min of storm rainfall. About 80% of the storms that generated debris flows lasted less than 3 h, with most of the rain falling in less than 1 h. The storms triggering debris flows ranged in average intensity between 1.0 and 32.0 nun/h, and had recurrence intervals of two years or less. Threshold rainfall conditions for floods and debris flows sufficiently large to pose threats to life and property from recently burned areas in south-central, and southwestern, Colorado are defined by: I=6.5D(-0.7) and I=9.5D(-0.7), respectively, where I=rainfall intensity (in mm/h) and D=duration (in hours).Debris flows were generated from 68 recently burned areas in southern California in response to long-duration frontal storms. The flows occurred after as little as two hours, and up to 16 h, of low-intensity (2-10 mm/h) rainfall. The storms lasted between 5.5 and 33 h, with average intensities between 1.3 and 20.4 mm/h, and had recurrence intervals of two years or less. Threshold rainfall conditions for life-and property-threatening floods and debris flows during the first winter season following fires in Ventura County, and in the San Bernardino, San Gabriel and San Jacinto Mountains of southern California are defined by I=12.5D(-0.4), and I=7.2D(-0.4), respectively. A threshold defined for flood and debris-flow conditions following a year of vegetative recovery and sediment removal for the San Bernardino, San Gabriel and San Jacinto Mountains of I-14.0D(-0.5) is approximately 25 mm/h higher than that developed for the first year following fires.The thresholds defined here are significantly lower than most identified for unburned settings, perhaps because of the difference between extremely rapid, runoff-dominated processes acting in burned areas and longer-term, infiltration-dominated processes on unburned hillslopes. Crown Copyright (C) 2007 Published by Elsevier B.V. All rights reserved.