Physical model experiments for sediment supply to the old Rhine through induced bank erosion

Morán, Andrés Die; Abderrezzak, Kamal El Kadi; Mosselman, E.; Habersack, Helmut; Lebert, F; Aelbrecht, Denis; Laperrousaz, Eric

doi:10.1016/s1001-6279(14)60003-2

Cited by 26 publications

(18 citation statements)

References 20 publications

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“…Sediments were generated by the scour of the two pools and by bank erosion, both following the reduction in the area of the wetted section induced by the two groynes, while other sediments were produced from residual bedload transport within the main channel upstream of the restoration site [38]. These channel responses are in accordance with previous modeling and field reports [44,60,61]. Field monitoring showed that the flow velocities were reduced along the impacted section during the whole monitoring period (4 years) while maintaining the same range of flow velocities as measured during the pre-restoration period for both the upstream and the downstream sections (Figure 7.b).…”

Section: Channel Responses and Habitat Heterogeneitysupporting

confidence: 88%

“…This ecological action consisted of removing the bank protection and three old groynes built during the beginning of the 20 th century (Figure 2.d) and implementing two new transverse groynes within the flow channel to maximize flow velocities and shear stresses along the bank. The location and shape of these groynes had been previously defined through numerical and physical modeling to promote bank erosion, deliver sediment into the channel and avoid any damage to human construction due to uncontrolled lateral erosion [44].…”

Section: Study Areamentioning

confidence: 99%

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Effects of Transverse Groynes on Meso-Habitat Suitability for Native Fish Species on a Regulated By-Passed Large River

Chardon¹,

Schmitt²,

Piégay³

et al. 2020

Preprint

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River regulations ultimately degrade fluvial forms and morphodynamics and simplify riparian and aquatic habitats. For several decades, river restoration actions have been performed to recover geomorphic processes and diversify these habitats to enhance both river biodiversity and ecosystem services. The objective of this study is to provide quantitative feedback on the experimental restoration of a large regulated and by-passed river (the Upper Rhine downstream of the Kembs Dam, France/Germany). This restoration consisted of the construction of two transverse groynes and the removal of bank protection. A monitoring framework composed of topo-bathymetric surveys as well as flow velocity and grain size measurements was established to assess the channel morphodynamic responses and evaluate their effects on habitat suitability for five native fish species using habitat models. A riverscape approach was used to evaluate the landscape changes in terms of both the configuration and the composition, which cannot be considered with classic approaches (e.g., WUA). Our results show that the two transverse groynes and, to a lesser extent, bank erosion, which was locally enhanced by the two groynes, increased habitat diversity due to the creation of new macroforms (e.g., pools and mid-bars) and fining of the bed grain size. Using a riverscape approach, our findings highlight that the restoration improved lentic fish habitats (eel and juvenile nase species) due to slowing of the local current and the deposition of fine sediments downstream of both groynes. As a consequence, the restoration improved the habitat suitability of the studied reach for more fish species compared with the pre-restoration conditions. This study also demonstrates that the salmon habitats downstream of the restored reach were improved due to fining of the bed grain size. This finding highlights that for restorations aimed at fish habitats, the grain size conditions must be taken into consideration along with the flow conditions. Furthermore, the implementation of groynes, while not a panacea, can be a strategy for improving fish habitats on highly regulated rivers, but only when more functional and natural options are impossible due to major constraints.

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Section: Channel Responses and Habitat Heterogeneitysupporting

confidence: 88%

Section: Study Areamentioning

confidence: 99%

Effects of Transverse Groynes on Meso-Habitat Suitability for Native Fish Species on a Regulated By-Passed Large River

Chardon¹,

Schmitt²,

Piégay³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…This ecological action consisted of removing the bank protection and three old groynes built during the beginning of the 20th century ( Figure 1d) and implementing two new transverse groynes within the flow channel to maximize flow velocities and shear stresses along the bank. The location and shape of these groynes had been previously defined through numerical and physical modeling to promote bank erosion, deliver sediment into the channel, and avoid any damage to human construction due to uncontrolled lateral erosion [45].…”

Section: Study Areamentioning

confidence: 99%

Effects of Transverse Groynes on Meso-Habitat Suitability for Native Fish Species on a Regulated By-Passed Large River: A Case Study along the Rhine River

Chardon

Schmitt

Piégay

et al. 2020

Water

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River regulations ultimately degrade fluvial forms and morphodynamics and simplify riparian and aquatic habitats. For several decades, river restoration actions have been performed to recover geomorphic processes and diversify these habitats to enhance both river biodiversity and ecosystem services. The objective of this study is to provide quantitative feedback on the experimental restoration of a large regulated and by-passed river (the Upper Rhine downstream of the Kembs Dam, France/Germany). This restoration consisted of the construction of two transverse groynes and the removal of bank protection. A monitoring framework composed of topo-bathymetric surveys as well as flow velocity and grain size measurements was established to assess the channel morphodynamic responses and evaluate their effects on habitat suitability for five native fish species using habitat models. A riverscape approach was used to evaluate the landscape changes in terms of both the configuration and the composition, which cannot be considered with classic approaches (e.g., Weighted Usable Area). Our results show that the two transverse groynes and, to a lesser extent, bank erosion, which was locally enhanced by the two groynes, increased habitat diversity due to the creation of new macroforms (e.g., pools and mid-bars) and fining of the bed grain size. Using a riverscape approach, our findings highlight that the restoration improved eel and juvenile nase species due to slowing down of the current and the deposition of fine sediments downstream of both groynes. As a consequence, the restoration improved the habitat suitability of the studied reach for more fish species compared with the pre-restoration conditions. This study also demonstrates that the salmon habitats downstream of the restored reach were improved due to fining of the bed grain size. This finding highlights that, for restorations aimed at fish habitats, the grain size conditions must be taken into consideration along with the flow conditions. Furthermore, the implementation of groynes, while not a panacea in terms of functional restoration, can be a strategy for improving fish habitats on highly regulated rivers, but only when more functional and natural options are impossible due to major constraints.

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“…This was built on an ecological diagnosis (Staentzel et al , ), a sociological analysis (Piquette, ), historical geomorphology (Arnaud et al , ), and morphodynamics. These morphodynamics include the combination of field experiments, geomorphic monitoring, and hydro‐dynamic modelling (Koll et al , ; Béraud, ; Die Moran et al , ). Artificial gravel augmentation, with a particle size finer than the armoured riverbed, has been identified as requiring in situ testing because of limitations in the current models for predicting bedload entrainment and associated channel change.…”

Section: Study Sitementioning

confidence: 99%

Monitoring gravel augmentation in a large regulated river and implications for process‐based restoration

Arnaud

Piégay

Béal

et al. 2017

Earth Surf Processes Landf

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International audienceThe artificial gravel augmentation of river channels is increasingly being used to mitigate the adverse effects of river regulation and sediment starvation. A systematic framework for designing and assessing such gravel augmentations is still lacking, notably on large rivers. Monitoring is required to quantify the movement of augmented gravel, measure bedform changes, assess potential habitat enhancement, and reduce the uncertainty in sediment management. Here we present the results of an experiment conducted in the Rhine River (French and German border). In 2010, 23 000 m3 of sediments (approximately the mean annual bedload transport capacity) were supplied in a by-passed reach downstream of the Kembs dam to test the feasibility of enhancing sediment transport and bedform changes. A 620-m-long and 12-m-wide gravel deposit was created 8 km downstream from the dam. Monitoring included topo-bathymetric surveys, radio-frequency particle tracking using passive integrated transponder (PIT) tags, bed grain size measurement, and airborne imagery. Six surveys performed since 2009 have been described (before and after gravel augmentation, and after Q2 and Q15 floods). The key findings are that (i) the augmented gravel was partially dispersed by the first flood event of December 2010 (Q1); (ii) PIT tags were found up to 3200 m downstream of the gravel augmentation site after four years, but the effects of gravel augmentation could not be clearly distinguished from the effects of floods and internal remobilization on more than 3500 m downstream; (iii) linear and log-linear relationships linking bedload transport, particle mobility, and grain size were established; and (iv) combined bathymetry and PIT tag surveys were useful for evaluating potential environmental risks and the first morpho-ecological responses. This confirmed the complementary nature of such techniques in the monitoring of gravel augmentation in large rivers

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Physical model experiments for sediment supply to the old Rhine through induced bank erosion

Cited by 26 publications

References 20 publications

Effects of Transverse Groynes on Meso-Habitat Suitability for Native Fish Species on a Regulated By-Passed Large River

Effects of Transverse Groynes on Meso-Habitat Suitability for Native Fish Species on a Regulated By-Passed Large River

Effects of Transverse Groynes on Meso-Habitat Suitability for Native Fish Species on a Regulated By-Passed Large River: A Case Study along the Rhine River

Monitoring gravel augmentation in a large regulated river and implications for process‐based restoration

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