Abstract Palaeomeanders are characteristic features of meandering river floodplains. Some were abandoned several millennia ago and can be used as evidence for past fluvial patterns. Despite many observations of changes undergone by meandering rivers, little is known about long-term morphological adjustment of meanders. This paper reports on investigations conducted in two reaches located in the middle valley of the Cher River (northwestern Europe, France) to examine the readjustments of lowland meanders during the second half of the Holocene. The aim of our study was to provide new insights into the complex dynamics that control low-energy meandering rivers. LiDAR DEM spatial analyses coupled with geophysical surveys and observations of sediments enabled the identification and dating of thirteen palaeomeanders embedded in coarse sediments (sand and gravel) while the whole floodplain is covered by silty overbank deposits. Sedimentological, geochemical and pollen analyses combined with radiocarbon and OSL dating allowed us to reconstruct the chronology of the cutoff and the filling of palaeochannels. No palaeochannels older than ca 6000 yr cal. BP, and no palaeochannels younger than the eleventh–thirteenth centuries cal. AD were identified. This allowed us to distinguish two periods of meandering processes. (1) Our observations demonstrate the multi-millennia persistence of an active meandering pattern in a context of land use changes (ca 6000 yr cal. BP-eleventh–thirteenth centuries cal. AD). The preserved mobility of the river can be mainly interpreted as the result of the low cohesiveness of the bank material. Too few fine sediments were delivered during the proto-historical and historical periods to help stabilize the river course. (2) Following the eleventh–thirteenth centuries cal. AD, the fluvial system underwent a laterally stable phase. The many medieval and modern hydraulic engineering works reduced the specific stream power and prevented lateral erosion. The drastic decrease in the river's capacity to generate new meanders resulted in the disappearance of floodplain lakes and loss of habitat diversity.

中文翻译：

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欧洲西北部（法国雪儿河）近 6000 年来蜿蜒河流的重新调整：在人类强迫下从活跃的曲流河到稳定的河道

摘要 古蜿蜒是蜿蜒河流泛滥平原的特征。有些在几千年前就被遗弃了，可以用作过去河流模式的证据。尽管对蜿蜒河流经历的变化进行了许多观察，但对曲流的长期形态调整知之甚少。本文报告了在位于雪尔河中谷（欧洲西北部，法国）的两个河段进行的调查，以研究全新世后半期低地曲流的重新调整。我们研究的目的是为控制低能量蜿蜒河流的复杂动力学提供新的见解。LiDAR DEM 空间分析与地球物理调查和沉积物观测相结合，能够识别和测年嵌入粗沉积物（沙子和砾石）中的 13 条古河道，而整个漫滩都被粉质河岸沉积物覆盖。沉积学、地球化学和花粉分析与放射性碳和 OSL 测年相结合，使我们能够重建截止和古河道填充的年代学。没有超过约 6000 年 cal 的古通道。BP，并且没有比 11-13 世纪更年轻的古河道。AD被识别。这使我们能够区分两个时期的蜿蜒过程。(1) 我们的观察表明，在土地利用变化的背景下（大约 6000 年，BP-公元 11-13 世纪），活跃的蜿蜒模式持续了数千年。河流保持流动性主要可以解释为河岸材料低粘性的结果。在原始历史和历史时期输送的细小沉积物太少，无法帮助稳定河道。(2) 继十一至十三世纪之后。AD，河流系统经历了横向稳定阶段。许多中世纪和现代的水利工程降低了比流功率并防止了侧蚀。河流产生新曲流的能力急剧下降，导致洪泛区湖泊消失和栖息地多样性丧失。在原始历史和历史时期输送的细小沉积物太少，无法帮助稳定河道。(2) 继十一至十三世纪之后。AD，河流系统经历了横向稳定阶段。许多中世纪和现代的水利工程降低了比流功率并防止了侧蚀。河流产生新曲流的能力急剧下降，导致洪泛区湖泊消失和栖息地多样性丧失。在原始历史和历史时期输送的细小沉积物太少，无法帮助稳定河道。(2) 继十一至十三世纪之后。AD，河流系统经历了横向稳定阶段。许多中世纪和现代的水利工程降低了比流功率并防止了侧蚀。河流产生新曲流的能力急剧下降，导致洪泛区湖泊消失和栖息地多样性丧失。