How does grid-resolution modulate the topographic expression of geomorphic processes?
How does grid-resolution modulate the topographic expression of geomorphic processes?
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DOI：
10.5194/esurf-4-627-2016
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发表时间：
2016-08-08
影响因子：
3.4
通讯作者：
Furbish, David J.
中科院分区：
文献类型：
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作者：
Grieve, Stuart W. D.;Mudd, Simon M.;Furbish, David J.
在许多地方，通过使用高分辨率数字地形数据，我们研究塑造地球的过程的能力大大提高。然而，尽管近年来此类数据集的可用性显著增加，但许多具有重要地貌意义的地点仍然没有高分辨率的地形数据。在这里，我们的目标是约束我们如何能够理解表面过程，通过地形分析进行低分辨率数据。我们从点云中生成数字高程模型，网格分辨率范围从1到30米，涵盖了全球广泛使用的数据分辨率范围，在美国的三个地点。利用这些数据，曲率和网格分辨率之间的关系进行了探讨，以及对每个景观的山坡泥沙输运系数（D，在m（2）yr（-1））的估计。曲率，因此D，值被证明是一般不敏感的网格分辨率，特别是在景观与广泛的山顶和山谷。然而，曲率分布在平均值附近变得越来越密集，理论上的考虑表明，从具有尖锐山脊的景观中提取曲率时应谨慎。通过分析曲率和坡度的一维近似，探讨了曲率和坡度对网格分辨率的敏感性，为二维地形数据生成结果提供了理论依据。对两种从地形数据中提取河道的方法进行了试验。通道提取的几何方法，发现通过检测阈值的平面曲率的通道执行良好的分辨率高达30米，在所有三个景观。在同一分辨率范围内，成功地提取了坡面长度和起伏度等景观参数。这些参数可以用来检测景观瞬变和我们的研究结果表明，这样的工作不需要局限于高分辨率的地形数据。这项工作中提出的结果的综合表明，虽然高分辨率（例如，1米）的地形数据确实为地貌研究提供了令人兴奋的可能性，但只要仔细考虑如何进行分析，就可以在较低分辨率的数据中了解许多关键参数。
In many locations, our ability to study the processes which shape the Earth are greatly enhanced through the use of high-resolution digital topographic data. However, although the availability of such datasets has markedly increased in recent years, many locations of significant geomorphic interest still do not have high-resolution topographic data available. Here, we aim to constrain how well we can understand surface processes through topographic analysis performed on lower-resolution data. We generate digital elevation models from point clouds at a range of grid resolutions from 1 to 30 m, which covers the range of widely used data resolutions available globally, at three locations in the United States. Using these data, the relationship between curvature and grid resolution is explored, alongside the estimation of the hillslope sediment transport coefficient (D, in m(2) yr(-1)) for each landscape. Curvature, and consequently D, values are shown to be generally insensitive to grid resolution, particularly in landscapes with broad hilltops and valleys. Curvature distributions, however, become increasingly condensed around the mean, and theoretical considerations suggest caution should be used when extracting curvature from landscapes with sharp ridges. The sensitivity of curvature and topographic gradient to grid resolution are also explored through analysis of one-dimensional approximations of curvature and gradient, providing a theoretical basis for the results generated using two-dimensional topographic data. Two methods of extracting channels from topographic data are tested. A geometric method of channel extraction that finds channels by detecting threshold values of planform curvature is shown to perform well at resolutions up to 30m in all three landscapes. The landscape parameters of hillslope length and relief are both successfully extracted at the same range of resolutions. These parameters can be used to detect landscape transience and our results suggest that such work need not be confined to high-resolution topographic data. A synthesis of the results presented in this work indicates that although high-resolution (e.g., 1 m) topographic data do yield exciting possibilities for geomorphic research, many key parameters can be understood in lower-resolution data, given careful consideration of how analyses are performed.