Landslide densities associated with rainfall, stand age, and topography on forested landscapes, southwestern Washington, USA
Landslide densities associated with rainfall, stand age, and topography on forested landscapes, southwestern Washington, USA
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DOI：
10.1016/j.foreco.2010.01.051
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发表时间：
2010-05
影响因子：
3.7
通讯作者：
T. Turner;S. Duke;Brian R. Fransen;M. Reiter;A. J. Kroll;J. W. Ward;J. Bach;Tiffany E. Justice;R. Bilby
中科院分区：
文献类型：
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作者：
T. Turner;S. Duke;Brian R. Fransen;M. Reiter;A. J. Kroll;J. W. Ward;J. Bach;Tiffany E. Justice;R. Bilby
在森林景观中，山体滑坡发生率的增加会对水生生境和水质产生不利影响，并使森林再生所需的土壤资源消失和/或退化。因此，了解管理行动、自然因素和滑坡率之间的联系是土地管理者所需的重要信息。2007年12月初的一场不寻常的强大风暴在美国华盛顿西南部和俄勒冈州西北部造成了创纪录的洪水和数千起山体滑坡，并提供了一个难得的机会来研究自然因素和森林管理实践对山体滑坡密度的影响。从航空照片和系统的实地调查中收集了滑坡库存数据，以提供一个广泛的调查数据库，用于估算滑坡密度，并研究华盛顿威拉帕山152，000公顷森林景观中滑坡密度、降水、地形和林分年龄之间的关联。我们估计的概率检测滑坡的航空照片上的六层定义的森林林分年龄和广泛的降雨强度，表示为百分之一百年，24小时，最大降雨量。主要研究结果是，滑坡检测概率随着林龄的增加而下降，但在降雨强度之间相似。在1：12，000比例尺的航空照片上未检测到的现场检测到的山体滑坡的总体比例为39%。无论林分年龄或坡度等级，在100年降雨量的0 - 100%范围内很少发生滑坡。在较高的降雨强度，显着更高的滑坡密度发生在陡坡（> 70%的坡度）相比，较低的坡度斜坡，正如预期的那样。超过100年降雨量的150%，滑坡的密度在0 - 5年和6 - 10年的林分年龄类别比在11 - 20，21 - 30，31 - 40，41+类别大2.2 - 3倍。林龄的影响最强的降雨强度最高。我们的研究结果表明，地面的滑坡库存数据是必要的，以纠正从航空照片的检测偏差，制定合理的估计滑坡密度的环境梯度，如降雨量和地形，并作出公正的解释森林管理协会和滑坡发生之间的关系。
Elevated landslide rates in forested landscapes can adversely impact aquatic habitat and water quality and remove and/or degrade soil resources required for forest regeneration. As a result, understanding the associations between management actions, natural factors, and landslide rates is important information needed for land managers. An unusual and powerful storm in early December, 2007, caused record flooding and thousands of landslides across southwest Washington and northwest Oregon, USA, and provided a rare opportunity to examine the effects of both natural factors and forest management practices on landslide density. Landslide inventory data were collected from both aerial photos and systematic field surveys to provide a broad survey database that was used to develop estimates of landslide density and to examine associations between landslide density, precipitation, topography, and forest stand age across a 152,000ha forested landscape in the Willapa Hills, Washington. We estimated the probability of detecting landslides on aerial photos for six strata defined by forest stand age and a broad range of rainfall intensity, expressed as percent of the 100-year, 24-h, maximum rainfall. Key findings are that landslide detection probability decreased with increasing stand age, but was similar across rainfall intensities. The overall fraction of field-detected landslides that were not detected on 1:12,000-scale aerial photos was 39%. Very few landslides occurred in the 0–100% of 100-year rainfall category, regardless of stand age or slope gradient class. At higher rainfall intensities, significantly higher landslide densities occurred on steep slopes (>70% gradient) compared to lower gradient slopes, as expected. Above ∼150% of 100-year rainfall, the density of landslides was ∼2–3 times larger in the 0–5 and 6–10 year stand age categories than in the 11–20, 21–30, 31–40, and 41+ categories. The effect of stand age was strongest at the highest rainfall intensities. Our results demonstrate that ground-based landslide inventory data are required in order to correct for detection bias from aerial photos, develop reasonable estimates of landslide density across environmental gradients such as rainfall magnitude and topography, and make unbiased interpretations of relationships between forest management associations and landslide occurrence.