Slope distributions, threshold hillslopes, and steady-state topography
Slope distributions, threshold hillslopes, and steady-state topography
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DOI：
10.2475/ajs.301.4-5.432
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发表时间：
2001-04-01
影响因子：
2.9
通讯作者：
Montgomery, DR
中科院分区：
文献类型：
--
作者：
Montgomery, DR
数字高程模型的两个“稳定状态”的山脉，奥林匹克山脉（OM）和俄勒冈州海岸山脉（OCR），被用来研究坡度分布，阈值山坡的发展，和稳定状态的地形之间的关系。这些山脉的流域面积与坡度图表现出大量的分散，复杂的范围形式的分析理论和景观演变模型的比较。等高线图的密度，这样的数据揭示了一个吸引子的规模从山坡过程到通道过程的过渡，和对数箱平均显示的趋势，平行预测的稳定状态的侵蚀规律，但不同的速率法为五个不同的过程域：山坡，谷头，崩积，基岩，冲积河谷段。整个OM中100 km（2）区域（由10 X 10 km网格定义）计算的斜率直方图分别在活跃岩石隆起和沉积地形区域呈现近似正态分布或指数分布。OCR中的局部斜率分布也趋向于正态分布，但在斜率较缓的区域中，有些是左偏的。尽管基岩可蚀性和长期岩石隆起率梯度存在强烈对比，但在上述参考网格和10 km直径移动窗口上确定的平均坡度在OM核心中相对不变。与此相反，在OCR的平均斜率平行的纬度梯度的岩石隆起率和基岩可蚀性。因此，在OM和OCR的坡度分布反映了不同的阈值基岩和土壤覆盖的山坡和稳态地形的发展之间的关系。
Digital elevation models of two "steady-state" mountain ranges, the Olympic Mountains (OM) and Oregon Coast Range (OCR), are used to examine relationships between slope distributions, the development of threshold hillslopes, and steady-state topography. Plots of drainage area versus slope for these mountain ranges exhibit substantial scatter that complicates comparison of range form to analytical theories and landscape evolution models. Contour plots of the density of such data reveal an attractor at the scale of the transition from hillslope processes to channel processes, and log-bin averaging reveals trends that parallel predictions of steady-state erosion laws but with different rate laws for five distinct process domains: hillslopes, valley heads, and colluvial, bedrock, and alluvial valley segments. Slope histograms computed for 100 km(2) areas (defined by a 10 X 10 km grid) throughout the OM exhibit approximately normal or exponential distributions in areas of active rock uplift and depositional topography, respectively. Local slope distributions in the OCR also tend to be normally distributed, but some are left-skewed in areas with gentler slopes. Mean slopes determined both over the above referenced grid and a 10-km diam moving window are relatively invariant in the core of the OM in spite of strong contrasts in bedrock erodibility and gradients in long-term rock uplift rates. In contrast, the mean slopes in the OCR parallel latitudinal gradients in rock uplift rates and bedrock erodibility. Hence, the slope distributions in the OM and OCR reflect distinct relationships between development of threshold bedrock and soil-mantled hillslopes and steady-state topography.