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Nathalie Dubois Love Råman Vinnå Marvin Rabold Michael Hilbe Flavio S. Anselmetti Alfred Wüest Laetitia Meuriot Alice Jeannet Stéphanie Girardclos 《Sedimentology》2020,67(2):971-990
River engineering projects are developing rapidly across the globe, drastically modifying water courses and sediment transfer. Investigation of the impact of engineering works focuses usually on short-term impacts, thus a longer-term perspective is still missing on the effects that such projects have. The ‘Jura Water Corrections’ – the largest river engineering project ever undertaken in Switzerland – radically modified the hydrological system of Lake Biel in the 19th and 20th Century. The deviation of the Aare River into Lake Biel more than 140 years ago, in 1878, thus represents an ideal case study to investigate the long-term sedimentological impacts of such large-scale river rerouting. Sediment cores, along with new high-resolution bathymetric and seismic reflection datasets were acquired in Lake Biel to document the consequences of the Jura Water Corrections on the sedimentation history of Lake Biel. Numerous subaquatic mass transport structures were detected on all of the slopes of the lake. Notably, a relatively large mass transport complex (0·86 km2) was observed on the eastern shore, along the path of the Aare River intrusion. The large amount of sediment delivered by the Aare River since its deviation into the lake likely caused sediment overloading resulting in subaquatic mass transport. Alternatively, the dumping since 1963 in a subaquatic landfill of material excavated during the second phase of river engineering, when the channels flowing into and out of Lake Biel were widened and deepened, might have triggered the largest mass transport, dated to 1964 or 1965. Additional potential triggers include two nearby small earthquakes in 1964 and 1965 (MW 3·9 and 3·2, respectively). The data for this study indicate that relatively large mass transports have become recurrent in Lake Biel following the deviation of the Aare River, thus modifying hazard frequency for the neighbouring communities and infrastructure. 相似文献
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Bicarbonate Daily Variations in a Karst River: the Carbon Sink Effect of Subaquatic Vegetation Photosynthesis 总被引：7，自引：0，他引：7
Using the Guancun River, an underground stream-fed river, in Rong’an County of Guangxi, China as a case study, the daily biochemical cycle was examined in this paper based on the data collected a weeklong via high resolution data logger monitoring and high-frequency sampling. Furthermore, the loss of inorganic carbon along its flow path was estimated. Results show that chemical components of the groundwater input are quite stable, showing little change extent; while all of the chemical parameters from two downstream monitoring stations show diel variation over the monitoring period, suggesting that plant activity in the river has a strong influence on water chemistry of the river. The comparison of the input fluxes from the groundwater with the output fluxes of HCO3? estimated at the downstream monitoring station during the high-frequency sampling period shows a strong decrease of HCO3?, indicating that the river is losing inorganic carbon along its flow path. The loss is estimated to be about 1,152 mmol/day/m of HCO3? which represent about 94.9 kg/day of inorganic carbon along the 1,350 m section of the Guancun River. It means that HCO3? entering the river from karst underground stream was either consumed by plants or trapped in the authigenic calcite and thus constitutes a natural sink of carbon for the Guancun karst system. 相似文献
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Human activities such as river corrections and deviations, lake‐level regulations and installations of hydropower plants affect and often strongly modify natural processes in lacustrine systems. In 1714, the previously bypassing Kander River was deviated into peri‐alpine Lake Thun. This pioneering geo‐engineering project, the first river correction of such dimensions in Switzerland, doubled the water and sediment input to the lake. In order to evaluate the sedimentary consequences of the Kander River deviation, the lacustrine sediments were investigated using a combined approach of high‐resolution (3·5 kHz) reflection seismic data and sediment cores (maximum length 2·5 m). The significance of this study is increased by the possible hazard represented by ammunition dumped into the lake (from 1920 to 1960) and by the recent installation of a gas pipeline on the lake floor in 2007/2008. The first 130 years after the river deviation were dominated by an extremely high sediment input, which led to the frequent occurrence of subaquatic mass movements. Slope failures primarily occur due to rapid sediment accumulation, but were occasionally triggered in combination with earthquake‐induced shocks and lake‐level fluctuations. After 1840, mass‐movement activity and sedimentation rates decreased due to a reduced sediment input as the Kander River adjusted to its new base level and, to a smaller degree, by further engineering of the Kander River bed and gravel withdrawal at the Kander Delta. A further consequence of the Kander River deviation is that the shores around Lake Thun have been more frequently affected by flooding due to the increased water input. In the time span from 1850 to 2006, six historically and/or instrumentally documented flood events could be correlated to flood turbidites in the sediment cores. This study demonstrates the significant usefulness of lacustrine sediments, not only in archiving natural hazards and human impact but also in assessing the consequences of future anthropogenic interventions on lacustrine systems. 相似文献
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