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Climatic and hydrogeomorphic controls on sediment characteristics in the southern Sierra Nevada
Journal of Hydrology ( IF 6.4 ) Pub Date : 2022-08-06 , DOI: 10.1016/j.jhydrol.2022.128300
Mohammad Safeeq , Aliva Nanda , Joseph W. Wagenbrenner , Jack Lewis , Carolyn T. Hunsaker

The magnitude of sediment yield from headwater catchments is controlled by the interactions among hydrology, geomorphology, and soil disturbance. In montane regions like the Sierra Nevada, snow is one of the main factors controlling the timing and magnitude of hydrological fluxes. However, the role of snow on modulating spatial and temporal variation of sediment yield remains unclear. Using 120-site years of sediment yield data from 10 headwater catchments (drainage area 50–475 ha), we examined the sediment yield characteristics across an elevational gradient (1,777–2,381 m elevation) in the southern Sierra Nevada. Across space and time, we calculated an average annual suspended sediment yield of 62 ± 147 Mg/km2. In contrast, the measured mean annual bedload yield from the study catchments was small, 1.1 ± 2.4 Mg/km2. A linear mixed-effects model showed that maximum annual discharge alone can only explain 24 % (marginal R2 = 0.24) of the variance in sediment yield. Similarly, the hypsometric integral, which is often used as a metric for erosion susceptibility, showed no predictive power (marginal R2 = 0.005). As much as 65 % of the variance in sediment yield can be explained by fixed effects when snow related drivers (i.e., center of flow timing and aspect) were included in the model along with maximum annual discharge, suggesting a strong influence of snowmelt. Moreover, the relationship between area normalized suspended sediment yield (Qs) and unit discharge (Q) was significantly different between rain and snow events (p = 0.001). Both average slope (α) and exponent (β) terms of the Qs=αQβ relationship across the ten catchments were higher for rainfall (α=5.8,β=1.84) than those for snowmelt (α=3.1,β=1.77) events. As the erosion severity and power were higher during rainfall than the snowmelt events, a shift in the precipitation form from snow to rain under a warming climate will likely increase sediment yield. These results provide critical insights on background sediment yield in the southern Sierra Nevada and likely changes under future climate.



中文翻译:

内华达山脉南部沉积物特征的气候和水文地貌控制

来自源头集水区的泥沙产量的大小受水文、地貌和土壤扰动之间的相互作用控制。在像内华达山脉这样的山地地区,雪是控制水文通量时间和幅度的主要因素之一。然而,雪对调节产沙量时空变化的作用仍不清楚。使用来自 10 个源头集水区(流域面积 50-475 公顷)的 120 年的产沙量数据,我们检查了内华达山脉南部海拔梯度(1,777-2,381 米)的产沙量特征。跨越空间和时间,我们计算出年均悬浮泥沙产量为 62 ± 147 Mg/km 2. 相比之下,研究流域测得的平均年床载产量很小,为 1.1 ± 2.4 Mg/km 2。线性混合效应模型表明,仅最大年排放量只能解释 24%(边际R 2  = 0.24)的产沙量变化。类似地,通常用作侵蚀敏感性度量的 hypsometric 积分没有显示出预测能力(边际R 2  = 0.005)。当模型中包括与雪有关的驱动因素(即流动时间和方向的中心)以及最大年排放量时,高达 65% 的产沙量变化可以用固定效应来解释,这表明融雪的影响很大。此外,面积归一化悬沙产量之间的关系(Q s)和单位流量(Q)在雨雪事件之间存在显着差异(p =  0.001)。两者的平均斜率 (α) 和指数 (β) 的条款s=αβ十个流域的降雨量关系较高(α=5.8,β=1.84) 比融雪的 (α=3.1,β=1.77) 事件。由于降雨期间的侵蚀严重程度和力量高于融雪事件,因此在气候变暖下降水形式从雪到雨的转变可能会增加产沙量。这些结果为了解内华达山脉南部的背景沉积物产量以及未来气候下可能发生的变化提供了重要见解。

更新日期:2022-08-06
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