Changes of river bed pattern of a lowland river: effect of natural processes or anthropogenic intervention?
Changes of river bed pattern of a lowland river: effect of natural processes or anthropogenic intervention?
复制标题
低地河流河床格局的变化：自然过程的影响还是人为干预？
DOI：
10.1111/j.1468-0459.2011.00432.x
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
M. Słowik
中科院分区：
文献类型：
--
作者：
M. Słowik
摘要通过探地雷达和航空测量，研究了波兰西部奥布拉河下游河道形态的变化。该河是一个强烈的人为改造的例子，然而，在其下游的河流格局变化的起源并不明显。使用配备屏蔽250-MHz天线的georadar MALIGAN ProEx进行GPR测量。地质雷达数据的三维分析与岩性信息的支持表明了多通道模式的痕迹。河道砂坝内沉积物分层方向的变化以及河道深度和宽度的差异表明了河床迁移方向的变化。对航空照片和卫星图像的分析表明，从地质雷达推断出的通道中只有少数可以辨别出来。原因可能是超过1米厚的细砂层覆盖了所有的冲积结构。对18世纪和19世纪的历史地图的分析表明，250年前，奥布拉河是一条蜿蜒的河流。这些地图还说明了几个曲流截止点和减少的湿地表面。河床形态发生了如下变化：1.从辫状河到曲流河，这可能是由气候和泥沙输移速率变化引起的自然过程，在其他低地河流中也观察到了这一点。2.从蜿蜒到曲折的模式与海峡岛屿，然后到曲折与牛轭湖。然而，需要进一步研究观察到的变化的原因和时间。
Abstract GPR and aerial surveys were conducted to study changes of channel pattern in the lower course of the Obra River (western Poland). The river is an example of an intensive anthropogenic transformation, however, the origin of the river pattern changes in its lower course is not obvious. The GPR measurements were done using a georadar MALÅ ProEx equipped with a shielded 250-MHz antenna. A 3D analysis of the GPR data supported with lithologic information indicated traces of a multi‐channel pattern. A variable orientation of sediment layering within channel bars and differences in channels depth and width pointed to changes of direction of the river bed migration. Analysis of aerial photographs and a satellite image indicated that only a few of the channels inferred from GPR could be discerned. The reason could be the more than 1 m thick fine sands layer covering all the alluvial structures. Analysis of historical maps from the eighteenth and the nineteenth centuries showed that 250 years ago the Obra was a meandering river. The maps illustrate also several meander cutoffs and decreased wetlands surface. The following transformations of the river bed pattern were discerned: 1. From braided to meandering channel pattern which could be a natural process caused by climatic and sediment transport rate changes that was also observed in case of other lowland rivers. 2. From meandering to sinuous pattern with channel islands and then to sinuous with oxbow lakes. However, further research is needed to study reasons and timing of the observed changes.