Abstract Multi-thread gravel-bed rivers in Europe have undergone distinctive changes in morphology related to progressive narrowing and incision during the last 100 years. In many cases, the post-effects of multi-thread channel transformations are associated with sediment deficits caused by channelization, damming, or land use changes. Similar trends of channel narrowing and incision can be observed in the Moravka River in the Czech Carpathians, where damming, in particular, has led to sediment deficits and decreases in flood events. Evaluation of the planform dynamics of vegetation in the active channel, lateral and vertical erosion in the channel and calculations of the dominant discharge were used as tools to define potential measures for the protection and sustainability of the close-to-natural multi-thread Moravka River channel. The successive vegetation rapidly colonised originally non-vegetated gravel-bar patches, controlling sediment material reinforcement. This process strongly contributed to a decrease in the number of gravel bars in recent decades and a decline in multi-thread channel dynamics. The total volumes of approximately 36,000 m3 and 3000 m3 of sediment material were eroded in an approximately 1-km-long reach during a high-magnitude flood (with ~20-year recurrence interval of mean daily discharge) and the ordinal high-flow event (with ~1-year recurrence interval of mean daily discharge), respectively, which led to an overall sediment material deficit in the studied reach. No single value of dominant discharge for sediment transport was found by bedload transport simulations because the volumes of transported material continuously increased with the magnitude of a particular discharge and its duration. Based on these findings, the main potential measures for the protection and sustainability of multi-thread channels are recommended. The artificial disturbance of successive vegetation cover on gravel bars and the occurrence of artificial flooding are crucial factors that could increase the multi-thread Moravka River channel dynamics. The artificial supply of gravel- and cobble-sized sediment material is necessary to stop the propagation of the ‘hungry water effect’ and incision due to the present sediment deficit in the studied reach.

中文翻译：

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中高山环境中多线砾石层河流的退化：定量分析和可能的解决方案

摘要 在过去的 100 年里，欧洲多线砾石床河流在形态上发生了与逐渐变窄和切割相关的明显变化。在许多情况下，多线程渠道转换的后效与渠道化、筑坝或土地利用变化引起的沉积物亏缺有关。在捷克喀尔巴阡山脉的莫拉夫卡河中可以观察到类似的渠道变窄和切口趋势，特别是在那里筑坝导致泥沙不足和洪水事件减少。活动河道植被的平面动态评估、河道中的横向和垂直侵蚀以及主要流量的计算被用作定义接近自然的多线程莫拉夫卡河的保护和可持续性的潜在措施的工具渠道。连续的植被迅速在原本没有植被的砾石滩上定居，控制了沉积物材料的强化。这一过程极大地促进了近几十年来砾石条数量的减少和多线程通道动力学的下降。在一次高强度洪水（平均日流量约 20 年的重复间隔）和有序的高流量事件期间，大约 36,000 立方米和 3000 立方米的沉积物材料在大约 1 公里长的河段内被侵蚀（平均日排放量约为 1 年的复发间隔），这导致所研究河段的总体沉积物材料不足。沉积物运输模拟没有发现沉积物运输的主要排放量的单一值，因为运输物质的体积随着特定排放量的大小及其持续时间而不断增加。基于这些发现，建议了多线程通道保护和可持续性的主要潜在措施。砾石坝上连续植被覆盖的人为干扰和人为洪水的发生是增加多线程莫拉夫卡河河道动力学的关键因素。由于研究河段目前的沉积物不足，必须人工供应砾石和鹅卵石大小的沉积物材料，以阻止“饥饿水效应”和切口的传播。推荐了多线程通道保护和可持续性的主要潜在措施。砾石坝上连续植被覆盖的人为干扰和人为洪水的发生是增加多线程莫拉夫卡河河道动力学的关键因素。由于研究河段目前的沉积物不足，必须人工供应砾石和鹅卵石大小的沉积物材料，以阻止“饥饿水效应”和切口的传播。推荐了多线程通道保护和可持续性的主要潜在措施。砾石坝上连续植被覆盖的人为干扰和人为洪水的发生是增加多线程莫拉夫卡河河道动力学的关键因素。由于研究河段目前的沉积物不足，必须人工供应砾石和鹅卵石大小的沉积物材料，以阻止“饥饿水效应”和切口的传播。