Monitoring sediment transport in a run-of-river hydropower dam was investigated to detect and quantify the siltation processes using Sentinel-2/MSI satellite images. We developed a method allowing us to assess the fate of sediment discharge in reservoirs and to map the locations of eroding and silting stream cross sections. This monitoring was achieved by retrieving the seasonal and interannual variation in suspended sediment concentration (SPM) longitudinally and by developing indices to detect local deviations from the overall SPM trend. A comparison between Sentinel-2 reflectance, processed for atmospheric and glint correction, and field measurements showed fine accuracy for the b8a/b4 band ratio (RMSE = 0.23 sr, N = 50) as well as a very good SPM retrieval performance for a wide range of concentrations [10–926 mg/L] with an RMSLE of 0.23 mg/L. SPM trend analysis demonstrated that significant (p < 0.001) sedimentation processes (i.e., decreases in SPM concentration upstream to downstream) occur for most parts of the hydrological cycle except during peak flooding when there was no significant SPM siltation. The overall rate of SPM decrease is −0.52 mg/L/km, varying from +0.11 mg/L/km down to −1.10 mg/L/km. We developed a deviation index to detect local anomalies from the overall upstream–downstream satellite-derived SPM trend. A satellite-derived map of eroding and silting reaches is produced evidencing the control of the sediment transport pattern by geomorphological features, such as rapids. Using independent bathymetric surveys, we showed that satellite data allow the locations of eroding and silting river reaches to be correctly mapped.

中文翻译：

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Sentinel-2 MSI 图像时间序列揭示了亚马逊水电站大坝沉积过程的水文和地貌控制

研究了监测径流式水电站大坝中泥沙输送情况，以使用 Sentinel-2/MSI 卫星图像检测和量化淤积过程。我们开发了一种方法，使我们能够评估水库沉积物排放的命运，并绘制侵蚀和淤积河流横截面的位置图。这种监测是通过纵向检索悬浮泥沙浓度 (SPM) 的季节和年际变化并开发指数来检测与整体 SPM 趋势的局部偏差来实现的。经过大气和闪烁校正处理的 Sentinel-2 反射率与现场测量之间的比较显示，b8a/b4 波段比（RMSE = 0.23 sr，N = 50）具有良好的精度，并且在广泛的范围内具有非常好的 SPM 检索性能。浓度范围 [10–926 mg/L]，RMSLE 为 0.23 mg/L。 SPM 趋势分析表明，水文循环的大部分部分都会发生显着（p < 0.001）的沉积过程（即上游到下游的 SPM 浓度降低），但洪水高峰期间没有显着的 SPM 淤积。 SPM 总体下降率为-0.52 mg/L/km，从+0.11 mg/L/km 降至-1.10 mg/L/km。我们开发了一个偏差指数来检测来自卫星的上下游整体 SPM 趋势的局部异常。制作了一张由卫星提供的侵蚀和淤积河段地图，证明了急流等地貌特征对沉积物输送模式的控制。通过独立的水深测量，我们表明卫星数据可以正确绘制侵蚀和淤积河段的位置。