Using hilltop curvature to derive the spatial distribution of erosion rates
Using hilltop curvature to derive the spatial distribution of erosion rates
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DOI：
10.1029/2011jf002057
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发表时间：
2012-05-04
影响因子：
3.9
通讯作者：
Yoo, Kyungsoo
中科院分区：
文献类型：
--
作者：
Hurst, Martin D.;Mudd, Simon M.;Yoo, Kyungsoo
侵蚀速率决定了景观的形态，因此量化侵蚀速率是许多地貌研究的关键部分。直接测量侵蚀速率的方法既昂贵又耗时，而地形分析有助于快速预测侵蚀速率并覆盖大的空间范围。如果坡面泥沙通量与坡度呈非线性关系，则坡面曲率与侵蚀速率呈线性关系。在这方面的贡献，我们开发了新的技术来提取山顶网络和采样其相邻的山坡，以测试使用高分辨率（1米）的数字高程数据估计侵蚀率的山顶曲率的效用。在加州的费瑟河流域，已发表的和新的宇宙成因放射性核素分析表明，侵蚀速率的变化超过一个数量级（10至250毫米千年（-1））。山顶曲率随侵蚀速率的增加而增加，从而可以校准控制坡度和泥沙通量之间关系的山坡泥沙输运系数。有限制的泥沙输运效率允许估计侵蚀速率在整个景观绘制的空间分布的山顶曲率。此外，我们表明，山顶曲率继续增加后，梯度有限的山坡出现的侵蚀率上升。因此，山顶曲率可能反映更高的侵蚀速率比可以预测的山坡坡度，提供山顶上的土壤生产可以跟上侵蚀的步伐。最后，山顶曲率可以用来估计侵蚀率的景观进行了短暂的调整，不断变化的边界条件，如果山坡的响应时间尺度相对较短的渠道。
Erosion rates dictate the morphology of landscapes, and therefore quantifying them is a critical part of many geomorphic studies. Methods to directly measure erosion rates are expensive and time consuming, whereas topographic analysis facilitates prediction of erosion rates rapidly and over large spatial extents. If hillslope sediment flux is nonlinearly dependent on slope then the curvature of hilltops will be linearly proportional to erosion rates. In this contribution we develop new techniques to extract hilltop networks and sample their adjacent hillslopes in order to test the utility of hilltop curvature for estimating erosion rates using high-resolution (1 m) digital elevation data. Published and new cosmogenic radionuclide analyses in the Feather River basin, California, suggest that erosion rates vary by over an order of magnitude (10 to 250 mm kyr(-1)). Hilltop curvature increases with erosion rates, allowing calibration of the hillslope sediment transport coefficient, which controls the relationship between gradient and sediment flux. Having constraints on sediment transport efficiency allows estimation of erosion rates throughout the landscape by mapping the spatial distribution of hilltop curvature. Additionally, we show that hilltop curvature continues to increase with rising erosion rates after gradient-limited hillslopes have emerged. Hence hilltop curvature can potentially reflect higher erosion rates than can be predicted by hillslope gradient, providing soil production on hilltops can keep pace with erosion. Finally, hilltop curvature can be used to estimate erosion rates in landscapes undergoing a transient adjustment to changing boundary conditions if the response timescale of hillslopes is short relative to channels.