Effects of sediment bypass tunnels on grain size distribution and benthic habitats in regulated rivers

Auel, Christian; Kobayashi, Sohei; Takemon, Yasuhiro

doi:10.1080/15715124.2017.1360320

Cited by 18 publications

(24 citation statements)

References 22 publications

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“…This finding could be due to better environmental conditions below compared to above the SBT outlet. Related studies also reported a positive influence of SBT operations on macroinvertebrate e community composition in downstream reaches 14 , 16 , 17 . Specifically, Auel et al .…”

Section: Discussionmentioning

confidence: 68%

“…Likewise, Auel et al . 17 reported that macroinvertebrate richness and composition downstream of dam-fragmented rivers increased with increasing SBT operation time. Estimates of macroinvertebrate diversity in these studies were done using morphological identifications mainly categorized at the functional feeding group 17 , order 14 , or genus level 16 .…”

Section: Introductionmentioning

confidence: 99%

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Ecological influence of sediment bypass tunnels on macroinvertebrates in dam-fragmented rivers by DNA metabarcoding

Serrana

Yaegashi

Kondoh

et al. 2018

Sci Rep

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Sediment bypass tunnels (SBTs) are guiding structures used to reduce sediment accumulation in reservoirs during high flows by transporting sediments to downstream reaches during operation. Previous studies monitoring the ecological effects of SBT operations on downstream reaches suggest a positive influence of SBTs on riverbed sediment conditions and macroinvertebrate communities based on traditional morphology-based surveys. Morphology-based macroinvertebrate assessments are costly and time-consuming, and the large number of morphologically cryptic, small-sized and undescribed species usually results in coarse taxonomic identification. Here, we used DNA metabarcoding analysis to assess the influence of SBT operations on macroinvertebrates downstream of SBT outlets by estimating species diversity and pairwise community dissimilarity between upstream and downstream locations in dam-fragmented rivers with operational SBTs in comparison to dam-fragmented (i.e., no SBTs) and free-flowing rivers (i.e., no dam). We found that macroinvertebrate community dissimilarity decreases with increasing operation time and frequency of SBTs. These factors of SBT operation influence changes in riverbed features, e.g. sediment relations, that subsequently effect the recovery of downstream macroinvertebrate communities to their respective upstream communities. Macroinvertebrate abundance using morphologically-identified specimens was positively correlated to read abundance using metabarcoding. This supports and reinforces the use of quantitative estimates for diversity analysis with metabarcoding data.

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Section: Discussionmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Ecological influence of sediment bypass tunnels on macroinvertebrates in dam-fragmented rivers by DNA metabarcoding

Serrana

Yaegashi

Kondoh

et al. 2018

Sci Rep

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“…The bedload transport capacity of the Rein da Sumvitg River was determined by applying Equation (13) to the 15-min discharge data, while accounting for the energy dissipation by using Equation (16). The effective bedload transport is smaller than the bedload transport capacity due to limited sediment supply and follows q s /q s * = 0.45 according to [18].…”

Section: Of 27mentioning

confidence: 99%

“…Sediment-laden flows are diverted through SBTs around reservoir dams, so that the sediment transport is restored to pre-dam status. Thus, SBTs contribute to a sustainable use of reservoirs, while enhancing the eco-morphology and aquatic habitat quality of the downstream river reaches [8,[10][11][12][13][14][15][16]. However, the…”

Section: Introductionmentioning

confidence: 99%

Field Investigation on Hydroabrasion in High-Speed Sediment-Laden Flows at Sediment Bypass Tunnels

Müller-Hagmann

Albayrak

Auel

et al. 2020

Water

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Wear due to sediment particles in fluid flows, also termed 'hydroabrasion' or simply 'abrasion', is an omnipresent issue at hydraulic structures as well as in bedrock rivers. However, interactions between flow field, particle motion, channel topography, material properties and abrasion have rarely been investigated on a prototype scale, leaving many open questions as to their quantitative interrelations. Therefore, we investigated hydroabrasion in a multi-year field study at two Swiss Sediment Bypass Tunnels (SBTs). Abrasion depths of various invert materials, hydraulics and sediment transport conditions were determined and used to compute the abrasion coefficients k v of different abrasion models for high-strength concrete and granite. The results reveal that these models are useful to estimate spatially averaged abrasion rates. The k v -value is about one order of magnitude higher for granite than for high-strength concrete, hence, using material-specific abrasion coefficients enhances the prediction accuracy. Three-dimensional flow structures, i.e., secondary currents occurring both, in the straight and curved sections of the tunnels cause incision channels, while also longitudinally undulating abrasion patterns were observed. Furthermore, hydroabrasion concentrated along joints and protruding edges. The maximum abrasion depths were roughly twice the mean abrasion depths, irrespective of hydraulics, sediment transport conditions and invert material.Water 2020, 12, 469 2 of 27 prevailing hydraulics and sediment transport conditions in the SBTs, i.e., high-speed sediment-laden flows, can cause severe invert hydroabrasion, which provokes high maintenance cost and, in the worst case, endangering the tunnel stability [17].Hydroabrasion is a common phenomenon occurring not only in SBTs and at other hydraulic structures, e.g., weirs, flushing channels, bottom outlets and diversion tunnels, but also in high-gradient bedrock rivers. Hence, it plays an import role in river incision and landscape evolution. Hydroabrasion is defined as continuous material loss from a fixed, submerged surface caused by the contacts of solid particles transported in the flow [18,19]. Depending on the hydraulic conditions and sediment properties, such as size and shape, sediment particles can be transported in sliding, rolling, saltation, or suspension mode causing grinding, rolling, or saltation impact stresses on the surface, respectively. Among these, impacts of saltating bedload particles govern not only material loss at SBTs and hydraulic structures, but also long-term bedrock incision and landscape evolution by driving hydroabrasion and macroabrasion-a process of fracturing bedrock into pluckable sizes mediated by particle impacts [19][20][21][22][23].Prediction of hydroabrasion is crucial for design service life analysis of invert materials used in hydraulic structures as well as for landscape evolution studies with potential applications in steep bedrock channels and channel knickpoint evolutions of exposed bedrock, such as waterfall...

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“…The flushing of sediment is one opportunity for so-called active management by the establishment of (i) density current venting [15], (ii) configuration of reservoirs [16], and (iii) sediment bypass tunnels [17,18]. However, here not only fines are diverted but also bedload [19]. The ecological consequences of an increased surplus of fines were studied in laboratories, e.g., [20,21] as well as in field investigations, e.g., [22,23].…”

Section: Introductionmentioning

confidence: 99%

Controlled Reservoir Drawdown—Challenges for Sediment Management and Integrative Monitoring: An Austrian Case Study—Part A: Reach Scale

Hauer

Haimann

Holzapfel

et al. 2020

Water

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For Europe, a reduction of 80% of the potential storage volume due to reservoir sedimentation is predicted by 2080. Sedimentation processes trigger the decrease of the storage volume and a related restriction in hydropower production. Further, the artificial downstream flushing of deposited fines has manifold effects on the aquatic ecology, including changes in morphology and sediment quality, as well as increased turbidity and subsequent stress for aquatic species. However, it is common to lower the water surface of reservoirs for technical inspections, which is not comparable to reservoir flushing operations. The presented case study deals with such a controlled drawdown beyond the operational level of the Gepatsch reservoir (Tyrol, Austria). Based on the awareness of possible ecological consequences, an advanced set of measures and an integrative monitoring design, consisting of a detailed event-based quantification of suspended sediments, changes in the morphology, especially with respect to fine sediments, and analyses of the biological quality element fish on the reach scale along the Inn River have been developed.

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Effects of sediment bypass tunnels on grain size distribution and benthic habitats in regulated rivers

Cited by 18 publications

References 22 publications

Ecological influence of sediment bypass tunnels on macroinvertebrates in dam-fragmented rivers by DNA metabarcoding

Ecological influence of sediment bypass tunnels on macroinvertebrates in dam-fragmented rivers by DNA metabarcoding

Field Investigation on Hydroabrasion in High-Speed Sediment-Laden Flows at Sediment Bypass Tunnels

Controlled Reservoir Drawdown—Challenges for Sediment Management and Integrative Monitoring: An Austrian Case Study—Part A: Reach Scale

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