EFFECT OF SUCTION DYNAMICS ON EQUIREBLEUM PROFILE OF SANDY BEACH UNDER STORM WAVE CONDITION

The role of morphodynamic features such as grain size, swash climate and wave action on the macrofauna of beaches are well-known. However, few studies have investigated natural disturbances as potential drivers of temporal community variations. In southeastern Brazil, we sampled the intertidal macrofauna of two sandy beaches to test whether seasonal disturbances as the frequency of storm wave events (SWE) and rainfall have significant influence on their composition and abundance. The macrofauna assemblage differed significantly between the rainy and the dry seasons, but rainfall was not the main driver of community changes, although both beaches are in the vicinity of extensive river plumes. Actually, SWE explained most macrofauna richness overtime, with positive effects. Our results point to the importance of learning more about the effects of poorly studied disturbances on macrofaunal communities, and based on them we strongly recommend including these seasonal phenomena when monitoring sandy beaches.

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Laboratory investigation on morphology response of submerged artificial sandbar and its impact on beach evolution under storm wave condition

Marine Geology ◽

10.1016/j.margeo.2021.106668 ◽

2021 ◽

pp. 106668

Author(s):

Yuan Li ◽

Chi Zhang ◽

Weiqi Dai ◽

Dake Chen ◽

Titi Sui ◽

...

Keyword(s):

Laboratory Investigation ◽

Wave Condition ◽

Storm Wave

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RECOVERY OF SANDY BEACH AFTER TYPHOON WAVES - CASE STUDY ON CHIGASAKI COAST

Coastal Engineering Proceedings ◽

10.9753/icce.v36v.papers.42 ◽

2020 ◽

pp. 42

Author(s):

Toshinori Ishikawa ◽

Takaaki Uda ◽

Jun-ichi Hosokawa ◽

Toshiro San-nami

Keyword(s):

Sandy Beach ◽

Sand Transport ◽

Storm Event ◽

Shore Protection ◽

Wave Condition ◽

Storm Waves ◽

Wave Conditions ◽

Typhoon Waves ◽

Time Required

Beach topography quickly changes in response to the action of storm waves, resulting in erosion of the foreshore with accretion under a calm wave condition after a storm. These seasonal beach changes may occur on beaches with protective measures or artificial beaches produced by beach nourishment. On these beaches, the shore protection function of a sandy beach is reduced when a trough is formed immediately offshore of the shoreline and the foreshore slope increases, indicating the importance of the study on topographic changes. Moreover, the time required for a beach recovery in response to wave conditions has not been sufficiently studied, along with the 3-D topographic changes associated with beach cycles. In this study, we aim to investigate these issues using the Narrow Multi-Beam survey data, wave data, and seabed materials data, taking the Chigasaki coast as an example. It was found that a seabed shallower than 2 and 3 m depths was eroded by rapid offshore sand transport during a storm event with the deposition of sand in a zone between 3 and 5 m depths, and then the beach recovered within 1-2 years after the storm. It was also confirmed that a bar and trough disappeared in 1-2 months under the conditions of HE = 0.5 m, TE = 8 s, and H/L = 0.005 when the crown depth of the bar was smaller than approximately 2 m. Thus, the topography after the storm waves recovers within several months or 1-2 years depending on wave conditions and the crown depth of the bar.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/W_P_3p_xd8U

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Storm Waves at the Shoreline: When and Where Are Infragravity Waves Important?

Journal of Marine Science and Engineering ◽

10.3390/jmse7050139 ◽

2019 ◽

Vol 7 (5) ◽

pp. 139 ◽

Cited By ~ 6

Author(s):

Oliver Billson ◽

Paul Russell ◽

Mark Davidson

Keyword(s):

Deep Water ◽

Water Wave ◽

Sandy Beach ◽

Transport Processes ◽

Infragravity Waves ◽

Storm Wave ◽

Wave Conditions ◽

Gravel Beaches ◽

Deep Water Wave ◽

Sand And Gravel

Infragravity waves (frequency, f = 0.005–0.05 Hz) are known to dominate hydrodynamic and sediment transport processes close to the shoreline on low-sloping sandy beaches, especially when incident waves are large. However, in storm wave conditions, how their importance varies on different beach types, and with different mixes of swell and wind-waves is largely unknown. Here, a new dataset, comprising shoreline video observations from five contrasting sites (one low-sloping sandy beach, two steep gravel beaches, and two compound/mixed sand and gravel beaches), under storm wave conditions (deep water wave height, H0 up to 6.6 m, and peak period, Tp up to 18.2 s), was used to assess: how the importance and dominance of infragravity waves varies at the shoreline? In this previously unstudied combination of wave and morphological conditions, significant infragravity swash heights (Sig) at the shoreline in excess of 0.5 m were consistently observed on all five contrasting beaches. The largest infragravity swash heights were observed on a steep gravel beach, followed by the low-sloping sandy beach, and lowest on the compound/mixed sites. Due to contrasting short wave breaking and dissipation processes, infragravity frequencies were observed to be most dominant over gravity frequencies on the low-sloping sandy beach, occasionally dominant on the gravel beaches, and rarely dominant on the compound/mixed beaches. Existing empirical predictive relationships were shown to parameterize Sig skillfully on the sand and gravel beaches separately. Deep water wave power was found to accurately predict Sig on both the sand and gravel beaches, demonstrating that, under storm wave conditions, the wave heights and periods are the main drivers of infragravity oscillations at the shoreline, with the beach morphology playing a secondary role. The exception to this was the compound/mixed beach sites where shoreline infragravity energy remained low.

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A Simple Nozzle-Diffuser Duct Used as a Kuroshio Energy Harvester

Processes ◽

10.3390/pr9091552 ◽

2021 ◽

Vol 9 (9) ◽

pp. 1552

Author(s):

Po-Hung Yeh ◽

Shang-Yu Tsai ◽

Wei-Ren Chen ◽

Shing-Nan Wu ◽

Meng-Chang Hsieh ◽

...

Keyword(s):

Energy Demand ◽

Energy Harvester ◽

Normal Wave ◽

Sea Surface ◽

Ocean Current ◽

Ansys Fluent ◽

Wave Condition ◽

Storm Wave ◽

Wave Conditions ◽

The Kuroshio

In response to the increasing energy demand in Taiwan and the global trend of renewable energy development, Kuroshio energy is a potential energy source. How to extract this invaluable natural resource has then become an intriguing and important question in engineering practices. This study reported the results of a feasibility study for a nozzle-diffuser duct (NDD) as the Kuroshio currents energy harvester. The computational fluid dynamics (CFD) software ANSYS Fluent was employed to calculate the drag and added mass coefficients of the duct anchored to the seabed. Those coefficients were further imported into Orcaflex to simulate the motion of the duct under normal and storm wave conditions. Results showed that the duct was stable 25 m below the sea surface under normal wave conditions. When the wave condition changed to storm waves, the duct needed to dive into at least 90 m below the sea surface to regain its stability and obtain high power take-off (PTO). An optimal design nozzle-diffuser-duct was reported, and a PTO peak of 15 kW was expectable in the Kuroshio currents. Once a suitable offshore platform can be developed with sixty-six NDDs, a Megawatt Kuroshio ocean current power generation system is feasible in the near future.

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A Simple Nozzle-Diffuser Duct Used as a Kuroshio Energy Harvester

10.20944/preprints202107.0463.v1 ◽

2021 ◽

Author(s):

Po-Hung Yeh ◽

Shang-Yu Tsai ◽

Wei-Ren Chen ◽

Shing-Nan Wu ◽

Meng-Chang Hsieh ◽

...

Keyword(s):

Energy Demand ◽

Energy Harvester ◽

Normal Wave ◽

Sea Surface ◽

Ocean Current ◽

Ansys Fluent ◽

Wave Condition ◽

Storm Wave ◽

Engineering Practices ◽

The Kuroshio

In response to the increasing energy demand in Taiwan and the global trend of renewable energy development, Kuroshio energy is a potential energy source. How to extract this invaluable natural resource has then become an intriguing and important question in engineering practices. This study conducted a study for a nozzle-diffuser duct (NDD) as the Kuroshio currents energy harvester. The computational fluid dynamics (CFD) software ANSYS Fluent was employed to calculate the drag and added mass coefficients of the duct anchored to the seabed. Those coefficients were further imported into Orcaflex to simulate the motion of the duct under normal and storm wave conditions. Results showed that the duct was stable 25 m below the sea surface under normal wave condition. When the wave condition changed to storm waves, the duct needed to dive into at least 90 m below the sea surface to regain its stability and obtain high power take-off (PTO). An optimal design nozzle-diffuser-duct was reported and a PTO peak of 15 kW was expectable in the Kuroshio currents. Once a suitable offshore platform can be developed with sixty-six NDDs, a Megawatt Kuroshio ocean current power generation system is feasible in the near future.

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Extreme storm wave influence on sandy beach macrofauna with distinct human pressures

Marine Pollution Bulletin ◽

10.1016/j.marpolbul.2016.04.009 ◽

2016 ◽

Vol 107 (1) ◽

pp. 125-135 ◽

Cited By ~ 20

Author(s):

Phillipe M. Machado ◽

Leonardo L. Costa ◽

Marjorie C. Suciu ◽

Davi C. Tavares ◽

Ilana R. Zalmon

Keyword(s):

Sandy Beach ◽

Extreme Storm ◽

Storm Wave

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Vulnerability Analysis of Episodic Beach Erosion by Applying Storm Wave Scenarios to a Shoreline Response Model

Frontiers in Marine Science ◽

10.3389/fmars.2021.759067 ◽

2021 ◽

Vol 8 ◽

Author(s):

Tae-Kon Kim ◽

Changbin Lim ◽

Jung-Lyul Lee

Keyword(s):

Wave Height ◽

Wave Energy ◽

Vulnerability Analysis ◽

Coastal Development ◽

Beach Erosion ◽

Mathematical Function ◽

Observation Data ◽

Response Model ◽

Wave Condition ◽

Storm Wave

Recently, because of the influence of climate change on sea level change, there has been growing concern regarding the erosion of beaches, which play a role in reducing the damage caused by coastal disasters. However, despite these concerns, a comprehensive understanding of the morphodynamic relationship between hazard factors and beach erosion is still lacking. Therefore, in this study, a vulnerability analysis of beach erosion was conducted by applying the shoreline response model (SLRM) of bulk model type, which identifies the physical characteristics of relevant coefficients based on the suspended sediment movement processes. To characterize wave energy incidence, storm wave scenario modeling and extreme wave analysis were conducted using wave data of 40 years on the east coast of Korea provided by the National Oceanic and Atmospheric Administration. A dimensionless mathematical function representing the storm wave scenario was proposed as a function of the peak wave height. In addition, to examine whether the beach vulnerability curve (BVC) obtained from the SLRM is valid, it was compared with the long-term shoreline observation data conducted at Maengbang Beach. For the past 9 years, sand sampling and shoreline observations were performed at Maengbang Beach about 5 times a year. However, since observations were performed in time intervals of several months, the direct comparison with model results was impossible, so a comparative analysis through statistical analysis of shoreline variability was performed. The variability of the shoreline for each reference point followed a normal distribution with a standard deviation of approximately 7.1 m. As a result of comparing the BVC results obtained from these statistical characteristics with those obtained from the model, significant similarity was shown in the high wave condition. Finally, the model was performed on two factors (mean wave height and peak wave height) which appear in SWSF and three factors (wave energy at breaking point, beach response factor and beach recovery factor) which appear in SLRM, and by analyzing the results, an approximate formula for the BVC is derived. This novel BVC approximation equation provides an intuitive understanding of the factors that affect beach vulnerability as well as their importance, and estimates the beach buffer section required to prevent coastal facilities from being damaged by erosion during a specific period. The results of this study can help limit reckless coastal development and mitigate erosion damage.

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