Drainage reorganization induces deviations in the scaling between valley width and drainage area
Drainage reorganization induces deviations in the scaling between valley width and drainage area
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DOI：
10.5194/esurf-10-875-2022
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发表时间：
2022-09
影响因子：
3.4
通讯作者：
Elhanan Harel;L. Goren;O. Crouvi;H. Ginat;E. Shelef
中科院分区：
文献类型：
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作者：
Elhanan Harel;L. Goren;O. Crouvi;H. Ginat;E. Shelef
抽象的。山谷和河道的宽度影响着水系的水文、生态和地貌功能。在许多研究中，山谷和/或河道的宽度（W）被估计为流域面积（A）的幂律函数，W=kcAd。然而，在经历排水重组的河流系统中，流域面积分布的突然变化可能导致与其流域面积不成比例的山谷或河道宽度。由于谷的调整时间尺度较长，因此谷中的这种不连续性可能比通道中的更明显。因此，预计重组排水沟的流域宽度-面积比例将偏离未重组的排水沟。为了探索重组对流域宽度-流域面积缩放的影响，我们研究了以色列内盖夫沙漠中的12个山谷部分，分为未受干扰的，斩首的和反转的山谷。我们发现，流域面积指数的值，d，是较低的断头谷相对于未受干扰的山谷，但仍然是积极的。相反，反向山谷的特点是负的d指数，表明随着流域面积的增加，山谷变窄。在反向类别中，我们还通过方程W=kbAbSc探索了河道坡度（S）的独立影响，得出了B和c的负值和总体相似值。在一个反向的山谷部分的详细研究表明，山谷下游变窄，而通道加宽，这表明，如假设的那样，通道宽度调整更快重组后的流域面积分布。调整后的狭窄通道决定了反向山谷中形成流的宽度，这与跨越分水岭的断头谷的有意义的更宽的形成流形成对比。这种差异导致反向通道和斩首通道之间的单位流功率发生阶跃变化，可能导致“宽度反馈”，促进持续的鸿沟迁移和重组。我们的研究结果表明，山谷宽度面积缩放是一个潜在的工具，用于识别景观的影响排水重组。考虑到特定的重组尺度可以改善重组景观中侵蚀速率分布的估计。
Abstract. The width of valleys and channels affects the hydrology, ecology, and geomorphic functionality of drainage networks. In many studies, the width of valleys and/or channels (W) is estimated as a power-law function of the drainage area (A), W=kcAd. However, in fluvial systems that experience drainage reorganization, abrupt changes in drainage area distribution can result in valley or channel widths that are disproportional to their drainage areas. Such disproportionality may be more distinguished in valleys than in channels due to a longer adjustment timescale for valleys. Therefore, the valley width–area scaling in reorganized drainages is expected to deviate from that of drainages that did not experience reorganization. To explore the effect of reorganization on valley width–drainage area scaling, we studied 12 valley sections in the Negev desert, Israel, categorized into undisturbed, beheaded, and reversed valleys. We found that the values of the drainage area exponents, d, are lower in the beheaded valleys relative to undisturbed valleys but remain positive. Reversed valleys, in contrast, are characterized by negative d exponents, indicating valley narrowing with increasing drainage area. In the reversed category, we also explored the independent effect of channel slope (S) through the equation W=kbAbSc, which yielded negative and overall similar values for b and c. A detailed study in one reversed valley section shows that the valley narrows downstream, whereas the channel widens, suggesting that, as hypothesized, the channel width adjusts faster to post-reorganization drainage area distribution. The adjusted narrow channel dictates the width of formative flows in the reversed valley, which contrasts with the meaningfully wider formative flows of the beheaded valley across the divide. This difference results in a step change in the unit stream power between the reversed and beheaded channels, potentially leading to a “width feedback” that promotes ongoing divide migration and reorganization. Our findings demonstrate that valley width–area scaling is a potential tool for identifying landscapes influenced by drainage reorganization. Accounting for reorganization-specific scaling can improve estimations of erosion rate distributions in reorganized landscapes.