Geomorphology ( IF 3.819 ) Pub Date : 2021-01-05 , DOI: 10.1016/j.geomorph.2020.107589 Lenka Tlapáková; Tomáš Pánek; Šárka Horáčková
Fluvial terraces of headwater streams in mountainous forested areas provide important insight into the development of sensitive fluvial system in response to natural and anthropogenic changes. Usually they are poorly investigated because of incomplete preservation and difficulties with mapping caused by dense canopy cover. We utilized new high-resolution LiDAR data, field mapping, sedimentological analysis, pollen analysis and radiocarbon dating to reconstruct the evolution of fluvial terraces in seven headwater catchments located in the highest parts of Moravskoslezské Beskydy mountains (Western Carpathians, Czechia). In these catchments, we identified three Holocene river terraces set within older alluvial deposits or flysch bedrock. The oldest (TH) terrace has a minimum age of the onset of accumulation of ~9 ka, the minimum age of the middle (TM) terrace is ~4.4 ka, and that of the lowest (TL) terrace is ~0.7 ka. The formation of the TH and TM terraces was controlled by climatic deterioration during the Subboreal (~4.3 ka) and Subboreal/Subatlantic transitions (~2.9–2.6 ka), respectively. The lowest TL terrace is dominated by <500-year-old fine-grained overbank deposits, which we interpret as legacy sediments due to deforestation and shepherd activity during the so-called Wallachian colonization of the study area. Our study reveals peculiarities in the development of the river terraces of small mountainous forested sub-catchments: (i) the limited preservation of pre-Holocene river terraces, (ii) sensitivity to extreme climatic events, and (iii) the decisive role of combined effects of climate change and grazing and forest management in sediment delivery during the last several centuries.
山区森林地区源头河流的河流阶地为响应自然和人为变化的敏感河流系统的发展提供了重要见识。通常，由于保存不完全以及密密的树冠覆盖造成的制图困难，因此对它们的调查不力。我们利用新的高分辨率LiDAR数据，田间制图，沉积学分析，花粉分析和放射性碳测年重建了位于MoravskoslezskéBeskydy最高山区（西喀尔巴阡山脉，捷克）的七个水源流域河流阶地的演化。在这些流域中，我们确定了三个全新世河阶地，它们位于较老的冲积沉积物或粉煤灰基岩中。最早的（TH）阶地的最低成藏年龄约为9 ka，中（TM）阶的最小年龄为〜4.4 ka，而最低（TL）阶的最小年龄为〜0.7 ka。TH和TM阶地的形成分别受亚热带（〜4.3 ka）和亚热带/亚大西洋过渡带（〜2.9–2.6 ka）的气候恶化控制。最低的TL阶地由＜500年历史的细粒高岸沉积物所主导，我们将其解释为在研究区域的所谓的Wallachian殖民期间由于森林砍伐和牧羊活动而遗留的沉积物。我们的研究揭示了山区多森林小流域河流阶地发展的特殊性：（i）全新世前河流阶地的保存有限，（ii）对极端气候事件的敏感性，