Coarse sediment dynamics and low-head dams: Monitoring instantaneous bedload transport using a stationary RFID antenna

In mixed bedrock-alluvial rivers, the response of the system to a flood event can be affected by a number of factors, including coarse sediment availability in the channel, sediment supply from the hillslopes and upstream, flood sequencing, and coarse sediment grain size distribution. However, the impact of along-stream changes in channel width on bedload transport dynamics remains largely unexplored. We combine field data, theory, and numerical modeling to address this gap. Observations from two flood events in the Daan River gorge in western Taiwan suggest that coarse sediment evacuation and re-deposition can cause intra-flood changes of up to several meters in channel bed elevation that are distinct from measured before/after bed changes. We hypothesize that this could be related to the abrupt change in width between the 1 km long bedrock gorge and the river upstream and downstream. An analysis of the theoretical relationships between discharge, channel width, and bedload transport capacity shows that for a given slope, narrow channels transport bedload more efficiently than wide ones at low discharges, while wider channels are more efficient at high discharges. We used the model sedFlow to explore this effect, running a random sequence of floods through a channel with a narrow gorge section bounded upstream and downstream by wider reaches. Channel response to imposed floods is complex, as high and low discharges drive different spatial patterns of erosion and deposition, and the channel may experience both of these regimes during the peak and recession periods of each flood. Our modeling suggests that width differences alone can drive substantial variations in sediment flux and bed response, without the need for variations in sediment supply or mobility. Further, the deposition or erosion that takes place within a flood is often not reflected in the before/after changes to the bed, and this disconnect increases with increasing flood size.

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Coarse sediment dynamics in a proglacial fluvial system (Fagge River, Tyrol)

Geomorphology ◽

10.1016/j.geomorph.2013.10.021 ◽

2014 ◽

Vol 218 ◽

pp. 88-97 ◽

Cited By ~ 31

Author(s):

Henning Baewert ◽

David Morche

Keyword(s):

Sediment Dynamics ◽

Fluvial System ◽

Coarse Sediment

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Bedload dynamics in the rapidly changing paraglacial zone of a high alpine catchment

10.5194/egusphere-egu2020-21253 ◽

2020 ◽

Author(s):

Clemens Hiller ◽

Kay Helfricht ◽

Gabriele Schwaizer ◽

Severin Hohensinner ◽

Kerstin Wegner ◽

...

Keyword(s):

Bedload Transport ◽

Sediment Flux ◽

High Mountain ◽

Channel Network ◽

Scientific Debate ◽

Coarse Sediment ◽

Sediment Volume ◽

Mountain Environments ◽

Fluvial Transport ◽

Catchment Areas

High mountain environments have been confronted with rising temperatures and geomorphological changes over the past 150 years, with the considerable retreat of glaciers constituting one of the most pronounced impacts in the Alps. Concurrent degradation of permafrost in headwalls exposed from the downwasting ice and in periglacial hillslopes alongside glaciers causes increasing sediment flux onto glacier surfaces. The accumulation of supraglacial debris at the current glacier tongue promotes water-storage in debris-covered ice bodies and is assessed as an important source of sediment in the proglacial zone, since a close connection to the fluvial channel network can be assumed. The evolution of mountain streams, the degree of connectivity and conditional sedimentation-erosion effects significantly determine the dynamics in a generally unstable paraglacial landscape in which retreating glaciers provide high stream discharges while sediment is widely unconsolidated.In the recent scientific debate, the anticipated progressive shift from supply-limitation (fluvial transport overcapacity) to transport-limitation (abundance of sediment) in high alpine catchment areas is discussed. Thus, this study intends to contribute by investigating the connection of coarse sediment including supraglacial debris from the proglacial transition zone to downstream fluvial transport. Key aspect is the feedback between increasing debris cover and a shifting runoff regime due to a changing composition of glacier melt, snow melt and heavy rainfall events. In that respect, the focus will be on the dynamics of bedload transport and the proglacial coarse sediment budget.This study is part of the Hidden.Ice project and conducts in-depth monitoring of the connectivity, runoff measurements and geomorphological surveys at the LTER site Jamtalferner, Silvretta Range, Austria. Hydraulic modelling of the potential transport capacity supported by bedload trap measurements, the analysis of grain size distribution in the proglacial area and sediment volume changes calculated from UAV-based photogrammetry are aimed at raising knowledge on hydrological and geomorphological dynamics.

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Coarse sediment dynamics in a large glaciated river system: Holocene history and storage dynamics dictate contemporary climate sensitivity

Geological Society of America Bulletin ◽

10.1130/b35530.1 ◽

2020 ◽

Cited By ~ 1

Author(s):

Scott W. Anderson ◽

Kristin L. Jaeger

Keyword(s):

High Resolution ◽

Sediment Dynamics ◽

Past Century ◽

Alluvial Deposits ◽

White River ◽

Flow Modification ◽

The Past ◽

Coarse Sediment ◽

Decadal Scale ◽

Continental Glaciation

The gravel-bedded White River drains a 1279 km2 basin in Washington State, with lowlands sculpted by continental glaciation and headwaters on an actively glaciated stratovolcano. Chronic aggradation along an alluvial fan near the river’s mouth has progressively reduced flood conveyance. In order to better understand how forecasted climate change may influence coarse sediment delivery and aggradation rates in this lowland depositional setting, we assessed the contemporary delivery and routing of coarse sediment through the watershed; this assessment was based on a rich set of topographic, sedimentologic, and hydrologic data from the past century, with a focus on repeat high-resolution topographic surveys from the past decade. We found that most of the lower river’s contemporary bed-load flux originates from persistent erosion of alluvial deposits in the lower watershed. This erosion is a response to a drop in local base level caused by a major avulsion across the fan in 1906 and then augmented by subsequent dredging. The 1906 avulsion and modern disequilibrium valley profiles reflect landscape conditioning by continental glaciation and a massive mid-Holocene lahar. In the proglacial headwaters, infrequent large sediment pulses have accomplished most of the observed coarse sediment export, with exported material blanketing downstream valley floors; during typical floods, transported bed material is largely sourced from erosion of these valley floor deposits. Throughout the watershed, we observe decadal-scale coarse sediment dynamics strongly related to the filling or emptying of valley-scale sediment storage over 102−104 yr time scales, often in response to major disturbances that either emplace large deposits or influence their redistribution. Paraglacial responses in large watersheds are suggested to be inherently complicated and punctuated as a result of internal landform interactions and stochastic/threshold-dependent events. We argue, in combination, that Holocene disturbance, storage dynamics, and human flow modification make coarse sediment fluxes in the lower White River relatively insensitive to decadal climate variability. Results highlight the degree to which river sensitivity to contemporary disturbance, climatic or otherwise, may be contingent on local and idiosyncratic watershed histories, underscoring the need to unpack those histories while demonstrating the utility of watershed-scale high-resolution topography toward that end.

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Effect of low-head dams on reach-scale suspended sediment dynamics in coarse-bedded streams

Journal of Environmental Management ◽

10.1016/j.jenvman.2020.111452 ◽

2021 ◽

Vol 277 ◽

pp. 111452

Author(s):

Colm M. Casserly ◽

Jonathan N. Turner ◽

John J. O’ Sullivan ◽

Michael Bruen ◽

Craig Bullock ◽

...

Keyword(s):

Suspended Sediment ◽

Sediment Dynamics ◽

Low Head

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Validation of an Experimental Procedure to Determine Bedload Transport Rates in Steep Channels with Coarse Sediment

Water ◽

10.3390/w13050672 ◽

2021 ◽

Vol 13 (5) ◽

pp. 672

Author(s):

Veronica Carrillo ◽

John Petrie ◽

Luis Timbe ◽

Esteban Pacheco ◽

Washington Astudillo ◽

...

Keyword(s):

Transport Model ◽

Bedload Transport ◽

Experimental Results ◽

Experimental Procedure ◽

Coarse Sediment ◽

Sediment Size ◽

High Gradients ◽

Sediment Particles ◽

Bedload Sediment ◽

Steep Slopes

The current study presents an experimental procedure used to determine bedload sediment transport rates in channels with high gradients and coarse sediment. With the aim to validate the procedure for further investigations, laboratory experiments were performed to calculate bedload transport rates. The experiments were performed in a laboratory tilting flume with slopes ranging from 3% to 5%. The sediment particles were uniform in shape (spheres). The experiments were divided into four cases based on sediment size. Three cases of uniform sizes of 10 mm, 15 mm and 25 mm and a case with a grain size distribution formed with the uniform particle sizes were considered. From the experimental results a mathematical bedload transport model was obtained through multiple linear regression. The experimental model was compared with equations presented in the literature obtained for gravel bed rivers. The experimental results agree with some of the models presented in the literature. The closest agreement was seen with models developed for steep slopes especially for the highest slopes considered in the present study. Therefore, it can be concluded that the methodology used can be replicated for the study of bedload transport rates of channels with high gradients and coarse sediment particles to study more general cases of this process such as sediments with non-uniform shapes and sizes. However, a simplified model is proposed to estimate bedload transport rates for slopes up to 5%.

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Impact of low-head dams on bedload transport rates in coarse-bedded streams

The Science of The Total Environment ◽

10.1016/j.scitotenv.2020.136908 ◽

2020 ◽

Vol 716 ◽

pp. 136908 ◽

Cited By ~ 3

Author(s):

Colm M. Casserly ◽

Jonathan N. Turner ◽

John J. O'Sullivan ◽

Michael Bruen ◽

Craig Bullock ◽

...

Keyword(s):

Bedload Transport ◽

Low Head

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Numerical modelling of particle-fluid interaction in fluvial sediment transport

10.5194/egusphere-egu2020-10186 ◽

2020 ◽

Author(s):

Gaston Latessa ◽

Dong Xu ◽

Chunning Ji ◽

Manousos Valyrakis

Keyword(s):

Sediment Transport ◽

Flow Field ◽

Turbulent Flows ◽

River Flow ◽

Bedload Transport ◽

Momentum Exchange ◽

International Conference ◽

Fluvial Hydraulics ◽

Coarse Sediment ◽

Sediment Particles

Numerical simulations for the transport of coarse sediment particles in turbulent flows are performed, with particular emphasis on the energy and momentum exchange [1, 2, 3] between the two phases at the particle scale. &#160;The solid particles positions and velocities are solved through the Discrete Element Method (DEM), coupled with a Computational Fluid Dynamics (CFD) model which updates the dynamically evolving flow field through the numerical solution of the Reynolds Averaged of Navier-Stokes equations (RANS).At the core of this work, the coupling of these two models (DEM-CFD) based on the Fictitious Boundary Method, is analysed. The models have a high mesh resolution, by adopting a meshing strategy which aims at sufficiently discretising the flow field surrounding each particle. Smooth and rough bed cases are simulated, under a wide range of Reynolds numbers covering applications from particle entrainment, up to bulk bedload transport through rolling and saltation. The numerical results are benchmarked against experimental data obtained from controlled laboratory experiments [4, 5, 6].The implementation of coupled CFD-DEM models provides a very powerful tool for improving the understanding of fluid and particle physics in sediment transport. Particularly, the potential to perform a large number of validated numerical that robustly predict geomorphological changes in aquatic environments and fluvial systems.References[1] Valyrakis M., P. Diplas, C.L. Dancey, and A.O. Celik. 2008. Investigation of evolution of gravel river bed microforms using a simplified Discrete Particle Model, International Conference on Fluvial Hydraulics River Flow 2008, Ismir, Turkey, 03-05 September 2008, 10p.[2] Valyrakis M., Diplas P. and Dancey C.L. 2013. Entrainment of coarse particles in turbulent flows: An energy approach. J. Geophys. Res. Earth Surf., Vol. 118, No. 1., pp 42- 53, doi:340210.1029/2012JF002354.[3] P&#228;htz, Th., Clark, A., Duran, O., Valyrakis, M. 2019. The physics of sediment transport initiation, cessation and entrainment across aeolian and fluvial environments, Reviews of Gephysics, https://doi.org/10.1029/2019RG000679.[4] Valyrakis, M. & Pavlovskis, E. 2014. "Smart pebble&#8221; design for environmental monitoring applications, In Proceedings of the 11th International Conference on Hydroinformatics, Hamburg, Germany.[5] Valyrakis M., A. Alexakis. 2016. Development of a &#8220;smart-pebble&#8221; for tracking sediment transport. International Conference on Fluvial Hydraulics River Flow 2016, St. Liouis, MO, 8p.[6] Valyrakis, M., Farhadi, H. 2017. Investigating coarse sediment particles transport using PTV and &#8220;smart-pebbles&#8221; instrumented with inertial sensors, EGU General Assembly 2017, Vienna, Austria, 23-28 April 2017, id. 9980.

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