surf zone
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Coasts ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 73-89
Author(s):  
Ivana M. Mingo ◽  
Rafael Almar ◽  
Laurent Lacaze

Low tide terrace (LLT) beaches are characterised by a moderately steep beach face and a flat shallow terrace influencing the local hydro-morphodynamics during low tide. The upper beachface slope (β) and the terrace width (Lt) are the main morphological parameters that define the shape of LTT cross-shore beach profiles. This work aims at better understanding the behaviour of β and Lt and their link with the incoming wave forcing. For this purpose, our results are based on 3.5 years times series of daily beach profiles and wave conditions surveys at two different microtidal LTT beaches with similar sediments size but different wave climate, one at Nha Trang (Vietnam) and the other one at Grand Popo (Benin). While they look similar, two contrasting behaviour were linked to two sub-types of LTT regimes: the first one is surf regulated beaches (SRB) where the swash zone is highly regulated by the surf zone wave energy dissipation on the terrace, and the second is swash regulated beaches (SwRB) acting in more reflective regime where the terrace is not active and the energy dissipation is mainly produced in the swash zone, the terrace becomes a consequences of the high dynamics in the swash zone. Finally, extending the common view of an equilibrium beach profile as a power law of the cross-shore distance, the ability of a simple parametrized cubic function model with the Dean number as unique control parameters is proposed and discussed. This simple model can be used for the understanding of LLT environments but it can not be extended to the whole beach spectrum.


2021 ◽  
Vol 85 (4) ◽  
pp. 245-255
Author(s):  
Valéria Marques Lemos ◽  
Henrique Cabral ◽  
Stephanie Pasquaud ◽  
João Paes Vieira

The southern population of Mugil liza is distributed from Argentina (47°S) to the state of São Paulo, Brazil (23°S). Young mullets use the estuaries as nursery grounds, and prior to recruitment into estuaries they use the surf zone as a temporary habitat. Based on 12 consecutive months of sampling, this study used generalized linear models (GLM) to analyse the relationships between environmental variables and the presence and relative abundance of young mullets in the surf zone adjacent to six major estuaries in southern Brazil (between 29°S and 33°S). Young mullets were present in all seasons over the sampling period, but the probability of occurrence was higher in winter and was associated with low temperatures. The water temperature alone explained more than half of the total deviance of the GLM models for presence (23%) and abundance (21%) of young mullets in the surf zone. Site 2 (Rio Grande) had lower temperatures in the colder months, the highest probability of occurrence of all collection sites and the greatest abundance (n=3402) of young M. liza, which represented 52% of the total of individuals (n=6493) caught among the six sites sampled.


2021 ◽  
Vol 13 (23) ◽  
pp. 4907
Author(s):  
Adam M. Collins ◽  
Matthew P. Geheran ◽  
Tyler J. Hesser ◽  
Andrew Spicer Bak ◽  
Katherine L. Brodie ◽  
...  

Timely observations of nearshore water depths are important for a variety of coastal research and management topics, yet this information is expensive to collect using in situ survey methods. Remote methods to estimate bathymetry from imagery include using either ratios of multi-spectral reflectance bands or inversions from wave processes. Multi-spectral methods work best in waters with low turbidity, and wave-speed-based methods work best when wave breaking is minimal. In this work, we build on the wave-based inversion approaches, by exploring the use of a fully convolutional neural network (FCNN) to infer nearshore bathymetry from imagery of the sea surface and local wave statistics. We apply transfer learning to adapt a CNN originally trained on synthetic imagery generated from a Boussinesq numerical wave model to utilize tower-based imagery collected in Duck, North Carolina, at the U.S. Army Engineer Research and Development Center’s Field Research Facility. We train the model on sea-surface imagery, wave conditions, and associated surveyed bathymetry using three years of observations, including times with significant wave breaking in the surf zone. This is the first time, to the authors’ knowledge, an FCNN has been successfully applied to infer bathymetry from surf-zone sea-surface imagery. Model results from a separate one-year test period generally show good agreement with survey-derived bathymetry (0.37 m root-mean-squared error, with a max depth of 6.7 m) under diverse wave conditions with wave heights up to 3.5 m. Bathymetry results quantify nearshore bathymetric evolution including bar migration and transitions between single- and double-barred morphologies. We observe that bathymetry estimates are most accurate when time-averaged input images feature visible wave breaking and/or individual images display wave crests. An investigation of activation maps, which show neuron activity on a layer-by-layer basis, suggests that the model is responsive to visible coherent wave structures in the input images.


2021 ◽  
Vol 7 ◽  
Author(s):  
Reza Marsooli ◽  
Mohammad Jamous ◽  
Jon K. Miller

Coastal areas of State of New Jersey in the Northeastern United States are exposed to extreme wind waves generated by tropical cyclones in the Atlantic Ocean. Past studies suggest that the frequency and intensity of major hurricanes in the Atlantic basin would increase under high greenhouse gas emission scenarios. Furthermore, sea level observations have revealed that the local mean sea level along the coast of New Jersey is rising at a rate higher than that of the global sea level rise. The objective of this study is to quantify the combined influence of sea level rise (SLR) and hurricane climatology change on wave heights induced by major hurricanes off the coast of New Jersey. To this end, a coupled hydrodynamic-wave model is utilized to simulate wind waves for synthetic hurricanes generated for the climate conditions in the historical period of 1980–2000 and future period of 2080–2100 under the RCP8.5 high emission scenario. The synthetic storms are generated by a hurricane model for the climate conditions obtained from four different global climate models. The projections of future wave heights show statistically significant increases in the wave heights induced by major hurricanes. Under the combined effects of hurricane climatology change and a SLR of 1.19 m, the increase in the extreme wave heights 15% in back-bays and shallow waters of the nearshore zone and up to 10% in deeper coastal waters. It is found that SLR alone would result in a significant increase in the hurricane-induced wave heights in the present-day surf zone.


2021 ◽  
Vol 173 ◽  
pp. 112946
Author(s):  
Leonardo Martins Pinheiro ◽  
Enio Lupchinski Junior ◽  
Pablo Denuncio ◽  
Rodrigo Machado

2021 ◽  
Vol 9 (11) ◽  
pp. 1300
Author(s):  
Troels Aagaard ◽  
Joost Brinkkemper ◽  
Drude F. Christensen ◽  
Michael G. Hughes ◽  
Gerben Ruessink

The existence of sandy beaches relies on the onshore transport of sand by waves during post-storm conditions. Most operational sediment transport models employ wave-averaged terms, and/or the instantaneous cross-shore velocity signal, but the models often fail in predictions of the onshore-directed transport rates. An important reason is that they rarely consider the phase relationships between wave orbital velocity and the suspended sediment concentration. This relationship depends on the intra-wave structure of the bed shear stress and hence on the timing and magnitude of turbulence production in the water column. This paper provides an up-to-date review of recent experimental advances on intra-wave turbulence characteristics, sediment mobilization, and suspended sediment transport in laboratory and natural surf zones. Experimental results generally show that peaks in the suspended sediment concentration are shifted forward on the wave phase with increasing turbulence levels and instantaneous near-bed sediment concentration scales with instantaneous turbulent kinetic energy. The magnitude and intra-wave phase of turbulence production and sediment concentration are shown to depend on wave (breaker) type, seabed configuration, and relative wave height, which opens up the possibility of more robust predictions of transport rates for different wave and beach conditions.


2021 ◽  
Author(s):  
Zachary Gold ◽  
McKenzie Q. Koch ◽  
Nicholas K. Schooler ◽  
Kyle A. Emery ◽  
Jennifer E. Dugan ◽  
...  

Surf zones are highly dynamic marine ecosystems that are subject to increasing anthropogenic and climatic pressures, posing multiple challenges for biomonitoring. Traditional methods such as seines and hook and line surveys are often labor intensive, taxonomically biased, and can be physically hazardous. Emerging techniques, such as baited remote underwater video (BRUV) and environmental DNA (eDNA) are promising nondestructive tools for assessing marine biodiversity in surf zones of sandy beaches. Here we compare the relative performance of beach seines, BRUV, and eDNA in characterizing community composition of bony (teleost) and cartilaginous (elasmobranch) fishes of surf zones at 18 open coast sandy beaches in southern California. Seine and BRUV surveys captured overlapping, but distinct fish communities with 50% (18/36) of detected species shared. BRUV surveys more frequently detected larger species (e.g. sharks and rays) while seines more frequently detected one of the most abundant species, barred surfperch ( Amphistichus argenteus ). In contrast, eDNA metabarcoding captured 83.3% (30/36) of all fishes observed in seine and BRUV surveys plus 59 additional species, including 13 that frequent surf zone habitats. eDNA approaches showed significantly higher sensitivity than seine and BRUV methods and more consistently detected 29 of the 30 (96.7%) jointly observed species across beaches. The six species detected by BRUV/seines, but not eDNA either lacked reference sequences, were only resolved at higher taxonomic ranks (e.g. Embiotocidae surfperches), or were detected below occupancy thresholds. Low site-species overlap between methods limited comparisons of richness and abundance estimates, highlighting the challenge of comparing biomonitoring approaches. Despite potential for improvement, results overall demonstrate that eDNA can provide a cost-effective tool for long-term surf zone monitoring that complements data from seine and BRUV surveys, allowing more comprehensive surveys of vertebrate diversity in surf zone habitats.


2021 ◽  
pp. 259-270
Author(s):  
Izmail Kantarzhi ◽  
Alexander Gogin

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 397
Author(s):  
Muhammad Zikra ◽  
Shaskya Salsabila ◽  
Kriyo Sambodho

The Port of 2 × 110 MW Nagan Raya Coal Fired Steam Power Plant is one of the facilities constructed by the State Electricity Company in Aceh Province, Indonesia. During its operation, which began in 2013, the port has dealt with large amounts of sedimentation within the port and ship entrances. The goal of this study is to mitigate the sedimentation problem in the Nagan Raya port by evaluating the effect of maintenance dredging. Field measurements, and hydrodynamic and sediment transport modeling analysis, were conducted during this study. Evaluation of the wind data showed that the dominant wind direction is from south to west. Based on the analysis of the wave data, the dominant wave direction is from the south to the west. Therefore, the wave-induced currents in the surf zone were from south to north. Based on the analysis of longshore sediment transport, the supply of sediments to Nagan Raya port was estimated to be around 40,000–60,000 m3 per year. Results from the sediment model showed that sedimentation of up to 1 m was captured in areas of the inlet channel of Nagan Raya port. The use of a passing system for sand is one of the sedimentation management solutions proposed in this study. The dredged sediment material around the navigation channel was dumped in a dumping area in the middle of the sea at a depth of 11 m, with a distance of 1.5 km from the shoreline. To obtain a greater maximum result, the material disposal distance should be dumped further away, at least at a depth of 20 m or a distance of 20 miles from the coastline.


2021 ◽  
Vol 925 (1) ◽  
pp. 012052
Author(s):  
J Risandi ◽  
W S Pranowo ◽  
A R T D Kuswardani ◽  
S Husrin ◽  
T Solihuddin ◽  
...  

Abstract Wave energy dissipation on the surf zone is compensated with the increase of mean sea level, the so-called wave setup, within the area. This study used the numerical model Delft3D to investigate the dynamics of setup across the north coast region of West Java (Losari to Indramayu) influenced by monsoon variations. The wave forcing was obtained from previous field studies on Cirebon coastal region. The waves within the region were largely dissipated far from the coastline, mainly at the area between Babakan and Karangampel, due to the gentle slope of the North coast of Java. The waves approaching the shoreline were mainly influenced by the east monsoon associated with the longer fetch from that direction. The wave setup varied from ~0.03 to 0.15 m, with the maximum setup occurred near the coastline of the east (Losari) and west (Indramayu) parts of the model domain that consisted of steeper slopes. This, potentially inducing severe coastal inundation that became a serious problem across the coastlines. Meanwhile, the setup near the coastline of the middle area of the domain (Babakan to Karangampel) was very weak, which was correlated to the larger wave dissipation within the offshore area of that region.


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