Numerical Simulations of Sediment Transport and Scour around Mines

Swash zone morphodynamics is of great signi cance for nearshore morphological change, and it is important to provide reliable numerical prediction for beachface evolution in the swash zone. Most of the numerical work on swash zone morphodynamics carried out so far has focused primarily on beach evolution under one single swash event. In reality, multiple swash events interact, and these swash interactions have been recognised as important in the beachface evolution. Swash-swash interactions leads to energy dissipation, enhanced bed shear stresses and sediment transport (Puleo and Torres- Freyermuth, 2016). In this paper, we investigate the beachface evolution under two swash events using numerical simulations, in which shock-shock interactions are described by dam-break problems.

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Numerical Simulations of the 2004 Indian Ocean Tsunami Deposits Thicknesses and Emplacements

10.5194/nhess-2018-348 ◽

2018 ◽

Author(s):

◽

Musa Al'ala ◽

Hermann M. Fritz ◽

Mirza Fahmi ◽

Teuku Mudi Hafli

Keyword(s):

Sediment Transport ◽

Indian Ocean ◽

Numerical Simulations ◽

Field Data ◽

Numerical Models ◽

Indian Ocean Tsunami ◽

Tsunami Deposit ◽

Field Observations ◽

Tsunami Deposits ◽

2004 Indian Ocean Tsunami

Abstract. After more than a decade of recurring tsunamis, identification of tsunami deposits, a part of hazard characterization, still remains a challenging task not fully understood. The lack of sufficient monitoring equipment and rare tsunami frequency are among the primary obstacles that limit our fundamental understanding of sediment transport mechanisms during a tsunami. The use of numerical simulations to study tsunami-induced sediment transport was rare in Indonesia until the 2004 Indian Ocean tsunami. This study aims to couple two hydrodynamic numerical models in order to reproduce tsunami-induced sediment deposits, i.e., their locations and thicknesses. Numerical simulations were performed using the Cornell Multi-Grid Coupled Tsunami Model (COMCOT) and Delft3D. This study reconstructed tsunami wave propagation from its source using COMCOT, which was later combined with Delft3D to map the location of the tsunami deposits and calculate their thicknesses. Two Dimensional-Horizontal (2DH) models were used as part of both simulation packages. Lhoong, in the Aceh Besar District, located approximately 60 km southwest of Banda Aceh, was selected as the study area. Field data collected in 2015 and 2016 validated the forward modeling techniques adopted in this study. However, agreements between numerical simulations and field observations were more robust using data collected in 2005, i.e., just months after the tsunami (Jaffe et al., 2006). We conducted pit (trench) tests at select locations to obtain tsunami deposit thickness and grain size distributions. The resulting numerical simulations are useful when estimating the locations and the thicknesses of the tsunami deposits. The agreement between the field data and the numerical simulations is reasonable despite a trend that overestimates the field observations.

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Numerical Simulations of the Flow and Sediment Transport Regimes Surrounding a Short Cylinder

IEEE Journal of Oceanic Engineering ◽

10.1109/joe.2007.890986 ◽

2007 ◽

Vol 32 (1) ◽

pp. 249-259 ◽

Cited By ~ 14

Author(s):

Kimberly A. Hatton ◽

Diane L. Foster ◽

Peter Traykovski ◽

Heather D. Smith

Keyword(s):

Sediment Transport ◽

Numerical Simulations ◽

Short Cylinder ◽

Flow And Sediment Transport

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Accuracy Evaluation of Numerical Simulations to Calculate Sediment Transport in Harbor due to Tsunami

Journal of Japan Society of Civil Engineers Ser B2 (Coastal Engineering) ◽

10.2208/kaigan.68.i_396 ◽

2012 ◽

Vol 68 (2) ◽

pp. I_396-I_400

Author(s):

Takeshi KONDOU ◽

Tooru MORIMOTO ◽

Noriko FUJIMOTO ◽

Koji TONOMO ◽

Takemi SHIKATA

Keyword(s):

Sediment Transport ◽

Numerical Simulations ◽

Accuracy Evaluation

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Modeling groundwater-driven morphodynamic evolution of a gravel bed river in presence of riparian vegetation

10.5194/egusphere-egu21-10083 ◽

2021 ◽

Author(s):

Ilaria Cunico ◽

Damiano Fantin ◽

Annunziato Siviglia ◽

Walter Bertoldi ◽

Nico Bätz ◽

...

Keyword(s):

Sediment Transport ◽

Numerical Simulations ◽

Riparian Vegetation ◽

Main Channel ◽

Biomass Density ◽

Vegetation Growth ◽

Channel Mobility ◽

Gravel Bed ◽

Single Thread ◽

River Planform

The morphological trajectory of gravel bed rivers is often dictated by the interaction between riparian vegetation, flow and sediment transport. Vegetation encroachment on riverbed can significantly reduce channel mobility, preventing bank erosion and ultimately confining the river to a single-thread planform. The rate at which plants can encroach the riverbed has been mainly associated to the frequency and magnitude of flooding removing vegetation. However, recent observations indicate that the groundwater dynamics can drive distinct morphological patterns, because of its effect on the spatial distribution of vegetation and growth. However, the quantification of the processes that links groundwater to river morphological changes through vegetation remains unclear.Here we aim at investigating the ecomorphodynamics of a gravel bed river induced by spatial variations in vegetation density by means of numerical simulations. Our case study is a 3 km long reach of the Allondon river, Switzerland, characterized by a wandering river morphology and that underwent spatially contrasting river planform changes in the last decades. Field observations suggest that deep groundwater in the upper part of the reach limited vegetation growth over years, with the main channel keeping a larger active width and dynamic behavior. On the other hand, a shallower groundwater in the downstream part provided accessible water resources for plants, which encroached the riverbed and confined the channel into a single-thread type of morphology. We performed numerical simulations with the 2D shallow water model BASEMENT, considering a mobile bed composed by uniform sediment and including the main feedbacks between vegetation growth and erosion, the flow field, and the sediment transport processes. We set up the model parameters to reproduce different vegetation spatial distributions, associated with different groundwater depths, and investigated the effect of a 10-years return period flood on the river planform change.Model results highlight that a low vegetation biomass density, particularly at lower riverbed elevations, caused no significant effect on scour and deposition processes, favoring channel mobility and plant removal by uprooting. This behavior is in line with the observations in the groundwater-deep part of the reach. In contrast, the occurrence of high biomass density at low elevations reduced significantly the channel mobility and the river active width. In this case, vegetation was able to trigger sedimentation on bars and reduce scouring in the main channel, which are key processes for the formation of vegetated, stable riverbeds.This study represents a step forward to the understanding of the role of the complex link between vegetation dynamics and gravel bed rivers morphodynamics and shows the potential of ecomorphodynamic modeling to interpret river morphological trajectories.&#160;&#160;

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Unified model of sediment transport threshold and rate across subaqueous bedload, windblown sand, and windblown snow

10.5194/egusphere-egu21-7022 ◽

2021 ◽

Author(s):

Thomas Pähtz ◽

Yonghui Liu ◽

Yuezhang Xia ◽

Peng Hu ◽

Zhiguo He ◽

...

Keyword(s):

Sediment Transport ◽

Numerical Simulations ◽

Deterministic Model ◽

Field Measurements ◽

Model Parameters ◽

Data Sets ◽

Windblown Sand ◽

Grain Size And Shape ◽

Snow Conditions ◽

Fluvial Environments

Nonsuspended sediment transport (NST) refers to the sediment transport regime in which the flow turbulence is unable to support the weight of transported grains. It occurs in fluvial environments (i.e., driven by a stream of liquid) and in aeolian environments (i.e., wind-blown) and plays a key role in shaping sedimentary landscapes of planetary bodies. NST is a highly fluctuating physical process because of turbulence, surface inhomogeneities, and variations of grain size and shape and packing geometry. Furthermore, the energy of transported grains varies strongly due to variations of their flow exposure duration since their entrainment from the bed. In spite of such variability, we here propose a deterministic model that represents the entire grain motion, including grains that roll and/or slide along the bed, by a periodic saltation motion with rebound laws that describe an average rebound of a grain after colliding with the bed. The model simultaneously captures laboratory and field measurements and discrete element method (DEM)-based numerical simulations of the threshold and rate of equilibrium NST within a factor of about 2, unifying weak and intense transport conditions in oil, water, and air (oil only for threshold). The model parameters have not been adjusted to these measurements but determined from independent data sets. Recent DEM-based numerical simulations (Comola, Gaume, et al., 2019, https://doi.org/10.1029/2019GL082195) suggest that equilibrium aeolian NST on Earth is insensitive to the strength of cohesive bonds between bed grains. Consistently, the model captures cohesive windblown sand and windblown snow conditions despite not explicitly accounting for cohesion.

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