Channel migration, furcation, and vegetation succession are characteristic processes of braided gravel rivers in Alpine regions. These are associated with a frequent turnover of large parts of the active floodplain. However, more than one century of river regulation has reduced or destroyed most of these ecosystem dynamics. More recently, there have been attempts to restore at least some sections of degraded rivers, while there is little monitoring of the biogeomorphological dynamics of such rivers. Thus, we did a four‐year analysis of four representative sections of the upper River Isar in Southern Germany differing in their degree of naturalness. Dynamics of channels, gravel bars, and vegetation were recorded by drone images, and braiding and gravel indices were calculated. When comparing the near‐natural, semi‐natural, degraded or restored sections, there was a gradient of decreasing channel migration, gravel bank expansion, and bank erosion due to a reduced turnover frequency. Biogeomorphological variation among years correlated with log peak discharge within the four sections. In addition, the cover and height growth of vegetation increased with river degradation, and channel migration was positively related to the braiding index. The total turnover of the active river corridor and of the vegetation were positively correlated with log peak discharge within the four sections. The floodplain dynamics of the restored section were improved compared to the degraded section but did not reach a near‐natural state. Thus, Alpine river sections with contrasting degrees of naturalness differ in terms of habitat turnover and vegetation succession, and these characteristics can only partially be restored by local measures.

中文翻译：

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沿高山河流退化梯度的生物地貌洪泛区动态

河道迁移、分叉和植被演替是高山地区辫状砾石河的特征过程。这些与大部分活动洪泛区的频繁周转有关。然而，一个多世纪的河流治理已经减少或破坏了大部分生态系统动态。最近，人们试图恢复至少一些退化河流的河段，但对这些河流的生物地貌动态却很少进行监测。因此，我们对德国南部伊萨尔河上游自然程度不同的四个代表性河段进行了四年的分析。通过无人机图像记录河道、砾石坝和植被的动态，并计算辫状指数和砾石指数。当比较近自然、半自然、退化或恢复部分时，由于周转频率减少，河道迁移、砾石岸扩张和河岸侵蚀呈递减趋势。年份之间的生物地貌变化与四个剖面内的对数峰值流量相关。此外，植被覆盖度和高度增长随着河流退化而增加，河道迁移与辫状指数呈正相关。活跃河流廊道和植被的总周转量与四个断面内的对数峰值流量呈正相关。与退化部分相比，恢复部分的洪泛区动态有所改善，但并未达到接近自然的状态。因此，自然程度不同的高山河段在生境更替和植被演替方面存在差异，这些特征只能通过当地措施部分恢复。