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Signal crayfish burrowing, bank retreat and sediment supply to rivers: A biophysical sediment budget
Earth Surface Processes and Landforms ( IF 3.3 ) Pub Date : 2021-01-15 , DOI: 10.1002/esp.5070
H. Sanders 1, 2 , S.P. Rice 1 , P.J. Wood 1
Affiliation  

Burrowing into riverbanks by animals transfers sediment directly into river channels and has been hypothesised to accelerate bank erosion and promote mass failure. A field monitoring study on two UK rivers invaded by signal crayfish (Pacifastacus leniusculus) assessed the impact of burrowing on bank erosion processes. Erosion pins were installed in 17 riverbanks across a gradient of crayfish burrow densities and monitored for 22 months. Bank retreat increased significantly with crayfish burrow density. At the bank scale (<6 m river length), high crayfish burrow densities were associated with accelerated bank retreat of up to 253% and more than a doubling of the area of bank collapse compared with banks without burrows. Direct sediment supply by burrowing activity contributed 0.2% and 0.6% of total sediment at the reach (1.1 km) and local bank (<6 m) scales. However, accelerated bank retreat caused by burrows contributed 12.2% and 29.8% of the total sediment supply at the reach and bank scales. Together, burrowing and the associated acceleration of retreat and collapse supplied an additional 25.4 t km−1 a−1 of floodplain sediments at one site, demonstrating the substantial impact that signal crayfish can have on fine sediment supply. For the first time, an empirical relation linking animal burrow characteristics to riverbank retreat is presented. The study adds to a small number of sediment budget studies that compare sediment fluxes driven by biotic and abiotic energy but is unique in isolating and measuring the substantial interactive effect of the acceleration of abiotic bank erosion facilitated by biotic activity. Biotic energy expended through burrowing represents an energy surcharge to the river system that can augment sediment erosion by geophysical mechanisms.

中文翻译:

信号小龙虾穴居,河岸撤退和河流沉积物供应:生物物理沉积物预算

动物钻入河岸直接将沉积物转移到河道中,并被认为可加速河岸侵蚀并促进大规模破坏。对英国两条河中小龙虾(Pacifastacus leniusculus入侵)的河流进行的现场监测研究)评估了挖洞对河岸侵蚀过程的影响。侵蚀针安装在小龙虾洞穴密度梯度上的17个河岸中,并进行了22个月的监测。随着小龙虾洞穴密度的增加,河岸撤退量显着增加。在河岸规模(河长<6 m),与没有洞穴的河岸相比,小龙虾的洞穴密度高导致河岸撤退速度高达253%,并且河岸塌陷面积增加了一倍以上。通过挖掘活动直接提供的沉积物在河段(1.1 km)和当地河岸(<6 m)范围内分别占总沉积物的0.2%和0.6%。但是,由于洞穴引起的岸边退缩加速,在河床和岸边尺度上分别占总沉积物供应量的12.2%和29.8%。掘进以及随之而来的撤退和塌陷加速共同提供了另外的25个。-1 a -1的洪泛区沉积物集中在一个地点,这表明小龙虾可能会对精细的沉积物供应产生重大影响。首次提出了将动物洞穴特征与河岸撤退联系起来的经验关系。该研究增加了少量的沉积物预算研究,该研究比较了由生物能源和非生物能源驱动的沉积物通量,但在隔离和测量生物活性促进的非生物堤岸侵蚀加速的实质性交互作用方面独树一帜。通过挖掘而消耗的生物能源代表河流系统的能源附加费,可以通过地球物理机制加剧沉积物的侵蚀。
更新日期:2021-01-15
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