With rising air temperature and precipitation, water and sediment fluxes in the Source Region of the Yangtze River (SRYR) have increased since 2000s. Nonetheless, the response of braided river morphology to climate-driven water and sediment flux change is still unknown. Water bodies of 9 large braided rivers from 1990 to 2020 were extracted based on Google Earth Engine platform, and impacts of climate change on morphological indices and morphodynamic processes were quantified. A new segmentation method is presented to more precisely extract braided river water body when the branch width is less than an image pixel size. The warming and wetting trend led to vegetation cover increase. With the increase of water flux, the water area of each braided reach has increased in both flood and non-flood season. The 3–5 years mean annual erosion and accretion intensity (newly proposed in this study) of the channel shows three different trends of increasing, weakening, and unchanged over time. These three trends can be classified into three patterns in response to climate-change driven water and sediment flux change in the SRYR as follows: sediment increase constrained pattern (weakening or unchanged), sediment increase dominated pattern (increasing), and water increase dominated pattern (increasing or unchanged). In summary, the braided rivers in the SRYR showing consistent increasing of water area, general expansion of active channel, and increasing of erosion and accretion intensity for some of the rivers, with the climate-driven increasing water and sediment flux.

中文翻译：

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青藏高原大型辫状河河道形态特征及动力过程对气候驱动的水沙通量变化的响应


自2000年代以来，随着气温和降水量的上升，长江源区的水和泥沙通量不断增加。尽管如此，辫状河形态对气候驱动的水和泥沙通量变化的响应仍然未知。基于Google Earth Engine平台提取了1990—2020年9条大型辫状河水体，量化了气候变化对形态指标和形态动力过程的影响。提出了一种新的分割方法，可以在分支宽度小于图像像素大小时更精确地提取辫状河水体。变暖和湿润趋势导致植被覆盖增加。随着水通量的增​​加，无论洪水期还是非洪水期，各辫状河段水域面积均有所增加。河道3~5年平均年侵蚀和增生强度（本研究新提出的）随时间的推移呈现出增加、减弱和不变三种不同的趋势。这三种趋势可分为三种模式来响应气候变化驱动的SRYR水沙通量变化：沉积物增加受限模式（减弱或不变）、沉积物增加主导模式（增加）和水增加主导模式（增加或不变）。综上所述，南江河流域辫状河随着气候驱动的水沙通量增加，水域面积持续增加，活动河道普遍扩张，部分河流侵蚀增生强度加大。