Wave energy dissipation due to mudbanks formed off southwest coast of India

Volvaiker, Samiksha; Vethamony, P.; Rogers, W. Erick; Pednekar, P.; Babu, M.T.; DineshKumar, P.K.

doi:10.1016/j.ecss.2017.07.018

Cited by 18 publications

(14 citation statements)

References 42 publications

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“…In the cross-shore direction the steepness of the shelf will directly impact the loss of wave energy due to bottom friction with steeper and narrower shelves having a smaller effect on wave attenuation than wider and flatter shelves (Kurian and Baba, 1987). The effect of bed friction on wave attenuation has particular importance in presence of vegetation (Hardy et al, 1990;Möller, 2006;Stratigaki et al, 2014), porous seabeds (Torres-Freyermuth et al, 2017), reefs (Masselink and Pattiaratchi, 2001;Lowe et al, 2005) and presence of mud banks (Pereira et al, 2011;Samiksha et al, 2017).…”

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confidence: 99%

Longshore wave variability along non-straight coastlines

Silva

Murray

Strauss

2018

Estuarine, Coastal and Shelf Science

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The present paper demonstrates the role of wave direction and shoreline alignment on wave attenuation along a non-straight coastline. A numerical model was calibrated against measured data at six locations along a non-straight coastline and a hybrid method composed by wave case selection/simulation and nearshore time series reconstruction was applied to transfer 20 years of wave time series from offshore to nearshore. The results highlight the importance of the orientation of the coastline to different degrees of wave exposure to the wave attenuation process. The varying orientation of the coastline, at each of the six sites, resulted in non-uniform wave attenuation alongshore under different wave directions. The extreme wave conditions at each of the sites were also shown to vary significantly along the coast, e.g. ~18% alongshore (at-17 m Australian Height Datum-AHD) and as much as 34% from offshore (-70 m AHD) to nearshore (-17 m AHD). The results presented here reinforce the importance of assessing variations in wave attenuation along the coast as opposed to simply using the closest offshore wave dataset available. Improved understanding of nearshore wave attenuation along non-straight coastlines aids in better informing future coastal protection and management strategies.

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confidence: 99%

Longshore wave variability along non-straight coastlines

Silva

Murray

Strauss

2018

Estuarine, Coastal and Shelf Science

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“…Two cases of wave transformation were simulated: (i) waves that propagated in clear water and (ii) in water with viscous mud as a case study for a mudbank. In the second case, the concentration of sediment in water was set to 1500 kg/m 3 (this value was taken from earlier studies [14,15]). The cohesive sediment transport option is enabled in the model to account for the presence of suspended sediments in water, but its parameters are tuned so that the concentration of sediments in water remains constant during simulation.…”

Section: Methodsmentioning

confidence: 99%

“…A detailed analysis of wave spectral data showed that the wave spectrum follows a specific shape at both the field locations B1 and B2 ( Figure 1). It was observed that there is an additional frequency peak down the main peak of the wave spectrum and as the waves approach the shore, this peak becomes the main one, i.e., frequency downshifting occurs [14]. Typical examples of such spectra calculated on wave chronograms measured by the Datawell buoys at water depths of 15 and 7 m are shown in Figure 2.…”

Section: Introductionmentioning

confidence: 99%

“…However, the peculiarities and full details of these mechanisms are still unknown. A field experiment was conducted off Alleppey, Kerala, in May-July 2014, during mudbank occurrence along the coast (detailed description is given in [14]). A detailed analysis of wave spectral data showed that the wave spectrum follows a specific shape at both the field locations B1 and B2 ( Figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Frequency Downshifting in Wave Spectra in Coastal Zone and Its Influence on Mudbank Formation

Saprykina

Shtremel

Volvaiker

et al. 2020

JMSE

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The evolution of wind waves in coastal zones leads to changes in the shape of the wave spectrum. Along the coast of Kerala, due to the presence of mudbanks during the southwest monsoon, we could observe downshifting of the peak frequency in the wave spectral data. The present study aims at proving the mechanism of frequency downshifting and possible influence of the downshifting process on mudbank formation. The results of SWASH (Simulating WAves till SHore) modeling and bispectral analysis shows that frequency downshifting occurs due to the difference nonlinear triad interactions of the main frequency peak of the wave spectrum with frequencies of the infragravity range independent of the viscosity of the medium. The increase in wave dissipation accelerates frequency downshifting additionally, decreasing the wave energy in the main peak frequency. It is shown that frequency downshifting can be one of the possible wave mechanisms of mudbank formation due to essentially different wave attenuation coefficients at the beginning and end of this process. For muddy cohesive sediments, it will lead to formation with an erosive profile at first and then an accumulative profile, i.e., mudbank formation.

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“…The parameterization of NG assumes the mud layer to be thin, and thus directly provides an analytical asymptotic solution of kmud avoiding the costly iteration procedure. These parameterizations have been tested on an academic case (ROGERS & ORZECH, 2013) and recently for a realistic configuration (SAMIKSHA et al, 2017).…”

Section: èMes Journées Nationales Génie Côtier -Génie Civilmentioning

confidence: 99%

Mud and sand effects on wave propagation over the French Guiana coasts

Michaud¹,

Morio²,

Gensac³

et al. 2018

XVèmes Journées, La Rochelle

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The dampening effect of waves by soft mud layers is observed throughout the spectrum, in laboratory as well as on the Louisiana or Guyana coasts. Since the bi-layer theoretical approach of GADE (1958), several parameterizations have been proposed and implemented in wave numerical models but many efforts of calibrations and additional works are still required to obtain realistic representations of in situ processes. The Guyanese coasts are impacted by the Amazon sediments discharge. In fact, 20 to 30% of these sediments migrate longshore either in turbid or in mud banks forms due to the waves and current combined actions. These mud banks cause rapid coastline variations, leading to accretion, erosion and submersion risks. The French operational wave forecasting system at coastal scale is based on WAVEWATCH III ®, using an unstructured grid that covers the French Guiana with a resolution of 200 m nearshore. A first version of this system has been implemented in 2017 in the framework of the HOMONIM project (History, Observation, Modeling sea levels, joint SHOM and Météo-France project). However this first version doesn't include the effects of the mud and sand banks on waves. In this paper, we investigate the mud and sand effects on the wave propagation in order to improve the future version of the operational French Guiana configuration. Numerical tests on different bottom stress parameterizations are performed on a laboratory case, to assess the behaviour of WW3. A more realistic application on Guiana is carried out by the creation of a seabed map (grain size) and the use of a fine description of the characteristics and location of the mud banks, thanks to high resolution satellite imagery and in-situ data.

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Wave energy dissipation due to mudbanks formed off southwest coast of India

Cited by 18 publications

References 42 publications

Longshore wave variability along non-straight coastlines

Longshore wave variability along non-straight coastlines

Frequency Downshifting in Wave Spectra in Coastal Zone and Its Influence on Mudbank Formation

Mud and sand effects on wave propagation over the French Guiana coasts

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