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Changes of fluvial processes caused by the restoration of an incised mountain stream
Ecological Engineering ( IF 3.8 ) Pub Date : 2021-05-25 , DOI: 10.1016/j.ecoleng.2021.106286
Bartłomiej Wyżga , Maciej Liro , Paweł Mikuś , Artur Radecki-Pawlik , Józef Jeleński , Joanna Zawiejska , Karol Plesiński

The construction of a high check dam on mountain Krzczonówka Stream, Polish Carpathians, in the mid-20th century caused numerous detrimental changes to the downstream reach. In 2014 the check dam was lowered to make the structure passable for river biota. Before that, several block ramps were constructed in the deeply incised downstream reach to facilitate entrapment of the sediment expected to be released from the lowered check dam. When the check-dam lowering was underway, a flood flushed out from the dam reservoir a considerable amount of sediment that was efficiently trapped by the block ramps. To determine to what extent the environmental problems caused by the long-term sediment starvation of the stream were mitigated by the restoration works, one-dimensional hydraulic modelling of flood flows was performed for pre- (2013) and post-flood conditions (2015) in ten study cross-sections. Moreover, hydromorphological quality of the stream was determined before the onset of restoration activities (2012) and after their completion (2015). The flood of 2014 deposited about 15,650 m3 of bed material in the downstream reach, which re-established an alluvial channel bed and increased bed elevation by 0.50 m on average. Bed aggradation reduced flow capacity of the channel and increased water stages attained at given flood discharges. This significantly decreased bed shear stress and entrainable grain size of bed material. The proportion of the total flow conveyed over the floodplain and retention potential of the floodplain increased, although these effects were largely dependent on the amount of bed aggradation in the study cross-sections. The hydromorphological quality of the stream improved in 4 out of the 5 evaluated cross-sections, with 3 cross-sections being upgraded from moderate to good quality class. The study demonstrated effectiveness of block ramps in mitigating problems in the physical functioning of an incised mountain stream.



中文翻译:

恢复切开的山stream引起的河流过程变化

20世纪中叶,波兰喀尔巴阡山脉Krzczonówka溪流上修建了一座高止水坝,对下游河段造成了许多不利影响。2014年,降低了检查坝,使该结构可通过河流生物区系。在此之前,在深切的下游河段建造了数个坡道,以方便滞留预期从降低的止水坝释放的沉积物。当降坝降下时,洪水从坝库中冲出了大量泥沙,这些泥沙被拦河坝坡道有效地捕获了。为了确定修复工程在多大程度上减轻了河流长期沉积物匮乏所造成的环境问题,在十个研究断面中,对洪水前(2013年)和洪水后(2015年)条件进行了洪水水流的一维水力建模。此外,在恢复活动开始之前(2012年)和恢复活动完成之后(2015年)确定河流的水形态学质量。2014年的洪水沉积了约15,650 m3下游河床中的河床物质,重新建立了冲积河床河床,平均河床高程增加了0.50 m。在给定的洪水流量下,床层的凝结会降低河道的流量,并增加水位。这显着降低了床层的剪切应力和床层材料的可夹带颗粒尺寸。尽管这些影响在很大程度上取决于研究断面中河床积聚的量,但在洪泛区上输送的总流量比例和洪泛区的保留潜力增加了。在5个评估断面中,有4个断面的水流水文质量得到了改善,其中3个断面从中等质量等级升级为优质质量等级。

更新日期:2021-05-25
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