Combining airborne and terrestrial laser scanning for quantifying erosion and deposition by a debris flow event
Combining airborne and terrestrial laser scanning for quantifying erosion and deposition by a debris flow event
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DOI：
10.1016/j.geomorph.2011.08.024
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发表时间：
2012-02-01
期刊：
影响因子：
3.9
通讯作者：
Sass, Oliver
中科院分区：
文献类型：
--
作者：
Bremer, Magnus;Sass, Oliver
我们使用以前很少进行的陆上激光扫描(TLS)和机载激光扫描(ALS)相结合的方法，对奥地利阿尔卑斯山Halltal的一次重大泥石流事件所输送的泥沙体积进行了量化。由ALS数据(震前地表)得到的数字地形模型(DIM)与由TLS数据(震后地表)得到的数字地面模型(DTM)相结合。两个数据集在挖方和填方分析中进行比对和比较，以估计不同的体积。主要焦点在于对所应用方法的评估和准确性评估。事实证明，基于平点的两个数据集的配准是不够的；需要通过多站平差进行额外的配准，以最小化两个数据集之间的平均高度误差，体积误差小于10%，可与纯ALS运动相媲美。对于扫描分辨率较低的复杂地形，估计误差较大。数据处理中的一个特殊问题是研究区低矮而密集的灌木植被，这需要特别适应的滤波算法。观察到ALS数据高估了平均70厘米的地面高度，地面表现不充分。尽管有这些局限性，但该方法被证明适用于准确的极端事件量化。泥石流的起始区位于径流集中的基岩-泥石流界面。评估了5000至12,000立方米(3)的体积。体积估计对侵蚀比沉积特征更有效；这是因为侵蚀沟谷相对较深，计算不受事件前植被的影响。虽然所调查的三个集水区之一的侵蚀和沉积是平衡的，但其他两个集水区的淤积量高于检测到的侵蚀量。原因还没有完全弄清楚。水流的大小是由流域大小、地形特征和1946年一场重大野火造成的森林砍伐决定的。(C)2011爱思唯尔B.V.保留所有权利。
We quantified the sediment volume transported by a major debris flow event in the Halltal, Austrian Alps, using a combination of terrestrial (TLS) and airborne laser scanning (ALS) which has rarely been carried out before. A digital terrain model (DIM) derived from ALS data (pre-event surface) was combined with a DTM derived from TLS data (post-event surface). Both datasets were aligned and compared in a cut and fill analysis estimating differential volumes.The main focus lay on the evaluation and accuracy assessment of the applied method. Tie-point based registration of both datasets proved to be insufficient; additional alignment by Multi Station Adjustment was necessary to minimise the averaged height error between both datasets, amounting for a volumetric error of less than 10% which is comparable to pure ALS-campaigns. Larger errors were estimated for complex terrain with low scanning resolutions. A particular problem in data processing was the low and dense shrub vegetation in the study area which required a specifically adapted filter algorithm. An insufficient ground representation was observed for the ALS-data overestimating ground heights for averaged 70 cm. Despite these limitations, the approach proved to be suitable for accurate extreme event quantification.The starting zones of the debris flows lie at the bedrock-debris interface where runoff is concentrated. Volumes of 5000 to 12,000 m(3) were assessed. Volume estimation worked better for the erosional than for the depositional features; this is because the erosional gullies are relatively deep and the calculation is not affected by pre-event vegetation. While erosion and sedimentation are balanced for one of the three catchments investigated, the deposited volumes are higher than the detected eroded volumes for the other two. The reasons are not fully understood. The magnitude of the flows was determined by catchment size, topographical characteristics and deforestation by a major wildfire in 1946. (C) 2011 Elsevier B.V. All rights reserved.