Modeling tidal sand wave recovery after dredging:effect of different types of dredging strategies

The geological environments in the western of the North Yellow Sea(NYS) are comparatively complicated and pregnant with various geo-hazards. High-resolution sub-bottom seismic data and previous research progress have been used to examine marine geo-hazards’ types, acoustic reflection features, origins and disaster mechanisms. The results indicate that the hazardous types are complicated and multiple in the western of the NYS, including tidal sand ridge, sand wave, tidal erosion gutter, underwater shoal, shallow gas, buried paleo-channel, active fault, irregular bedrock and so on. They have some connections as well as differentiations in their distribution and genesis. This paper can provide the theoretical basis on marine engineering, disaster prevention and mitigation in the western of the NYS . More attention should be given to severe geo-hazards that can constitute direct or potential hazards to the economic development and engineering construction.

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Modeling tidal sand wave formation in a numerical shallow water model: The role of turbulence formulation

Continental Shelf Research ◽

10.1016/j.csr.2013.04.023 ◽

2013 ◽

Vol 60 ◽

pp. 17-27 ◽

Cited By ~ 16

Author(s):

B.W. Borsje ◽

P.C. Roos ◽

W.M. Kranenburg ◽

S.J.M.H. Hulscher

Keyword(s):

Shallow Water ◽

Wave Formation ◽

Water Model ◽

Sand Wave ◽

Shallow Water Model ◽

Tidal Sand

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Interaction Between Offshore Pipelines and Migrating Sand Waves

Volume 4: Offshore Geotechnics; Ronald W. Yeung Honoring Symposium on Offshore and Ship Hydrodynamics ◽

10.1115/omae2012-83875 ◽

2012 ◽

Author(s):

Jordan Matthieu ◽

Tim Raaijmakers

Keyword(s):

Wave Crest ◽

Sand Wave ◽

Offshore Pipelines ◽

Sand Waves ◽

Long Term Stability ◽

Wave Trough ◽

Migration Direction ◽

Operational Life ◽

Tidal Sand ◽

Wave Migration

Large areas of shallow, sandy seas are covered by migrating tidal sand waves. Sand wave migration rates are on the order of 10s of meters per year, with heights between 10 and 30% of the water depth. If such regions are traversed by pipelines, the dynamic interaction between the rock-berm protection of the pipelines and the migratory sand waves must be accounted for to assure the long term stability of both the rock-berms and pipelines. This study employs a 2DV model to demonstrate the hydrodynamic and morphodynamic interaction between migrating sand waves and a rock-berm constructed perpendicular to the migration direction. The timescale of sand waves and the design life of rock-berm are similar, consequently, rock-berms in sand wave regions experience a change in bed level approximately equal to that sand wave height. Due to the large difference in temporal scales between local erosive processes and sand wave migration, the passing of a sand wave is manifest as a general rising or falling of the ambient seabed, while a rock-berm is fixed at its construction elevation. Consequently, the critical design case is for a rock-berm constructed at a sand wave crest since the surrounding bed level decreases throughout the operational life of the pipeline. A conservative design approach is to construct rock berm protection in a sand wave trough, resulting in rising ambient seabed levels throughout the operational lifetime of the underlying pipeline or electrical cable.

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A CLASSIFICATION METHOD FOR THE PRESENCE OF TIDAL SAND WAVES AND MAINTENANCE DREDGING DESIGN

Coastal Engineering Proceedings ◽

10.9753/icce.v36.papers.48 ◽

2018 ◽

pp. 48

Author(s):

Rick De Koning ◽

Jaap van Thiel De Vries ◽

Bas Borsje

Keyword(s):

Large Scale ◽

Tidal Flow ◽

Narrow Channel ◽

Sand Wave ◽

Maintenance Strategies ◽

Sand Waves ◽

Recirculating Flow ◽

The North ◽

Tidal Sand ◽

And Migration

The study into sand wave dynamics in South Channel commenced after large dune forms were observed in monitoring campaigns following the channel deepening project of the Port of Melbourne. The project involved deepening of the harbor berths and channels, but more importantly, it involved the deepening of South Channel in Port Phillip Bay. South Channel, the main shipping channel, crosses the bay over â‰ˆ20km. The growth of bedforms at various locations in South Channel now threatens to impede marine traffic. The dimensions and migration rate of the bedforms in the channel are remarkable, especially in the harsh flow conditions in the narrow channel. Therefore, the bedforms in South Channel cannot be given an obvious classification. In this paper it is shown that the bedforms in South Channel can be classified as a tidal sand wave type with a method that requires only insight in water depth, tidal flow velocity and grain size. Tidal sand waves are large-scale bedforms generated by recirculating flow cells that drive sediment to the top of a crest and are commonly observed on shallow coastal seas such as the North Sea. The bedform concern in the channel illustrates the necessity of an evaluation of the present, and alternative, channel maintenance strategies. A numerical model in Delft3D software is applied, along with a probabilistic calculation that combines insights from the simulations and survey data, to assess different maintenance strategies.

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Sediment Characteristics over Asymmetrical Tidal Sand Waves in the Dutch North Sea

Journal of Marine Science and Engineering ◽

10.3390/jmse8060409 ◽

2020 ◽

Vol 8 (6) ◽

pp. 409 ◽

Cited By ~ 1

Author(s):

Chiu Hwa Cheng ◽

Karline Soetaert ◽

Bas Wijnand Borsje

Keyword(s):

Grain Size ◽

North Sea ◽

Sand Wave ◽

Experimental Investigations ◽

Sand Waves ◽

Offshore Engineering ◽

Organic Carbon Concentration ◽

Significant Difference ◽

Sediment Sorting ◽

Tidal Sand

The behavior of asymmetrical bedforms, which include many tidal sand waves, is challenging to understand. They are of particular interest since they are mostly located within areas prone to offshore engineering activities. Most experimental investigations regarding asymmetrical bedforms consider the riverine environment, are limited to a single sand wave or a few scattered ones, and focus only on differences between crest and trough. Hardly any information is available on sediment compositional changes along asymmetrical tidal sand waves, despite their abundance offshore. An asymmetrical sand wave field located off the coast of Texel Island in the North Sea was studied in June and October 2017. A total of 102 sediment samples were collected over two seasons along a single transect that covered five complete sand waves to measure the grain size composition, organic carbon concentration, chlorophyll-a (chl-a) concentration, and sediment permeability. We found significant variations in these sediment parameters between the sand wave trough, crest, and gentle and steep slopes, including a difference in permeability of more than 2-fold, as well as a difference in median grain size exceeding 65 µm. Based on these characteristics, a sand wave can be divided into two discrete halves: gentle slope + crest and steep slope + trough. Our results indicate a distinct sediment-sorting process along the Texel sand waves, with a significant difference between the two halves of each sand wave. These data could serve as input for process-based modeling of the link between sediment-sorting processes and seabed morphodynamics, necessary to design offshore engineering projects.

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Modelling the Past and Future Evolution of Tidal Sand Waves

Journal of Marine Science and Engineering ◽

10.3390/jmse9101071 ◽

2021 ◽

Vol 9 (10) ◽

pp. 1071

Author(s):

Janneke Krabbendam ◽

Abdel Nnafie ◽

Huib de Swart ◽

Bas Borsje ◽

Luitze Perk

Keyword(s):

Vertical Direction ◽

Skill Score ◽

The Other ◽

Sand Wave ◽

Sand Waves ◽

Future Evolution ◽

The North ◽

Skill Scores ◽

The North Sea ◽

Tidal Sand

This study focuses on the hindcasting and forecasting of observed offshore tidal sand waves by using a state-of-the-art numerical morphodynamic model. The sand waves, having heights of several meters, evolve on timescales of years. Following earlier work, the model has a 2DV configuration (one horizontal and one vertical direction). First, the skill of the model is assessed by performing hindcasts at four transects in the North Sea where sand wave data are available of multiple surveys that are at least 10 years apart. The first transect is used for calibration and this calibrated model is applied to the other three transects. It is found that the calibrated model performs well: the Brier Skill Score is ’excellent’ at the first two transects and ’good’ at the last two. The root mean square error of calculated bed levels is smaller than the uncertainty in the measurements, except at the last transect, where the M2 is more elliptical than at the other three transects. The calibrated model is subsequently used to make forecasts of the sand waves along the two transects with the best skill scores.

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Network response to internal and external perturbations in large sand-bed braided rivers

Earth Surface Dynamics Discussions ◽

10.5194/esurfd-3-197-2015 ◽

2015 ◽

Vol 3 (1) ◽

pp. 197-250

Author(s):

F. Schuurman ◽

M.G. Kleinhans ◽

H. Middelkoop

Keyword(s):

Large Scale ◽

Propagation Rate ◽

Sand Wave ◽

Bifurcation Instability ◽

Channel Network ◽

Morphological Effect ◽

Braided Rivers ◽

Braided Channel ◽

Different Types ◽

Order Of Magnitude

Abstract. The intrinsic instability of bars, bifurcations and branches in large braided rivers is a challenge to understand and predict. Even more, the reach-scale effect of human-induced perturbations on the braided channel network is still unresolved. In this study, we used a physics-based model to simulate the hydromorphodynamics in a large braided river and applied different types of perturbations. We analyzed the propagation of the perturbations through the braided channel network. The results showed that the perturbations initiate an instability that propagates in downstream direction by means of bifurcation instability. It alters and rotates the approaching flow of the bifurcations. The propagation celerity is in the same order of magnitude as the theoretical sand wave propagation rate. The adjustments of the bifurcations also change bar migration and reshape, with a feedback to the upstream bifurcation and alteration of the approaching flow to the downstream bifurcation. This way, the morphological effect of a perturbation amplifies in downstream direction. Thus, the interplay of bifurcation instability and asymmetrical reshaping of bars was found to be essential for propagation of the effects of a perturbation. The study also demonstrated that the large-scale bar statistics are hardly affected.

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Nonlinear dynamics of sand waves in sediment scarce environments

10.5194/egusphere-egu21-16019 ◽

2021 ◽

Author(s):

Johan Damveld ◽

Gaetano Porcile ◽

Paolo Blondeaux ◽

Pieter Roos

Keyword(s):

Environmental Parameters ◽

Sand Wave ◽

Average Height ◽

Nonlinear Behaviour ◽

Field Observations ◽

Marine Geology ◽

Geophysical Research ◽

Continuous Growth ◽

Sand Waves ◽

Tidal Sand

Field observations in the Dover Strait (Le Bot and Trentesaux, 2004) show sandy bed patterns in an environment where sand is scarce. Their morphological features closely resemble tidal sand waves, however, these type of bed forms are characterized by a crest-to-crest spacing which is larger than the wavelength of sand waves in the same surveyed area where sand is abundant. Based on stability theory, Porcile et al (2017) developed a morphodynamic model that was able to explain these features. They found that where the motionless substratum is exposed due to the growth of dunes, the lack of sand affects sediment transport, and consequently the morphology of the bed patterns. Their results also showed that the continuous growth leads to a lengthening of the dunes, and an increasing irregularity of the spacing. The found that their results were supported by the field observations.Since the model by Porcile et al (2017) is partly based on the perturbation principle, the results are only valid for small amplitude patterns. To further understand the nonlinear behaviour of these sand starved dunes (e.g. shape, height), we here apply the fully numerical sand wave model by Damveld et al (2020). We extend this model by accounting for the presence of a hard substrate just below a thin layer of sand. Moreover, we start with a randomly perturbed bed pattern to give the morphodynamic system the freedom of self-organization.Preliminary results show that the numerical model is able to reproduce the results found by Porcile et al (2017). In situations where sand is less abundant, wavelengths increase, and so does the spacing irregularity. Moreover, it is found that the average height of the sandy dunes is becoming increasingly smaller with decreasing sand availability. Further analysis should reveal dependencies to different environmental parameters, such as grain size, depth and tidal current strength.Le Bot, S., & Trentesaux, A. (2004). Types of internal structure and external morphology of submarine dunes under the influence of tide- and wind-driven processes (Dover Strait, northern France). Marine Geology, 211(1), 143-168. doi:10.1016/j.margeo.2004.07.002Damveld, J. H., Borsje, B. W., Roos, P. C., & Hulscher, S. J. M. H. (2020). Horizontal and Vertical Sediment Sorting in Tidal Sand Waves: Modeling the Finite-Amplitude Stage. Journal of Geophysical Research: Earth Surface, 125(10), e2019JF005430. doi:https://doi.org/10.1029/2019JF005430Porcile, G., Blondeaux, P., & Vittori, G. (2017). On the formation of periodic sandy mounds. Continental Shelf Research, 145(Supplement C), 68-79. doi:10.1016/j.csr.2017.07.011

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