scholarly journals CASE STUDY OF NEARSHORE CURRENTS HAZARD ANALYSIS FOR RECREATIONAL BEACH DEVELOPMENT

2020 ◽  
pp. 20
Author(s):  
Clint Chester Reyes ◽  
Eric Cruz ◽  
Jose Carlo Eric Santos
Keyword(s):  
Hazard Analysis ◽  
Safety Margin ◽  
Rip Currents ◽  
Waves And Currents ◽  
Wave Conditions ◽  
Deep Water Wave ◽  
Wave Hindcasting ◽  
Offshore Wave ◽  
Beach Resort ◽  
Resort Development

Nearshore current generation at two coastlines contemplated for beach resort development is studied with the use of a numerical model for coexisting waves and currents. A nested-mesh technique was applied to consolidate the 2 domains of coarse and fine bathymetric data and to translate deep water wave conditions at the nearshore mesh boundary. The hydrodynamic model is validated using tide data at the nearest tide stations, while offshore wave conditions, determined from a wave hindcasting method, are inputted as quasi-stationary forcing. Simulations results of wave-current co-existing fields indicate local areas of rip currents within the project coastlines. In order to evaluate the safe swimming zones, an analysis of threshold currents under idealized conditions of human characteristics was carried out, that indicated a threshold of 0.16 mps for pure currents. With a safety margin to account for co-existing waves, rip current zones not exceeding 0.1 mps are considered safe and are used to designate the safe swimming areas for the 2 locations.

South Baltic rip currents detected by a field survey

Baltica ◽  
2020 ◽  
Vol 33 (1) ◽  
pp. 11-20
Author(s):  
Rafał Ostrowski ◽  
Jan Schönhofer ◽  
Magdalena Stella ◽  
Alexey Grave ◽  
Aleksander Babakov ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Maximum Velocity ◽  
Experimental Investigations ◽  
Rip Currents ◽  
The South ◽  
Storm Waves ◽  
Circulation Patterns ◽  
Wave Conditions ◽  
Deep Water Wave ◽  
Russian Research

The paper presents results of experimental investigations of currents in the nearshore region of the south Baltic Sea. The analysis is based on the field data collected near Lubiatowo (Poland) using the measuring equipment which was simultaneously operated both by the Polish and Russian research teams. The venture was aimed at detection of rip currents that are rare and insufficiently explored phenomena in the south Baltic coastal zone. The data include wind velocity and direction, deep-water wave buoy records and currents surveyed by means of drifters. The measurements were carried out in the area whose hydrodynamics, lithodynamics and morphodynamics are typical of the south Baltic sandy coast. It appears that the nearshore water flows are mostly represented by longshore wave-driven currents with mean velocities of 0.22–0.53 m/s, and the maximum velocity of 1.32 m/s. Water circulation patterns resembling rip currents with velocities of up to 0.34 m/s were identified only on one day, when specific wave conditions occurred at the study site. Contrary to strong longshore currents generated by storm waves, rip currents occur under mild or moderate wave conditions, when many beach users are willing to swim in nearshore waters. The present findings can therefore be useful for the improvement of swimmers’ safety in the south Baltic Sea regions.

scholarly journals Wave-Induced Sediment Motion Beyond the Surf Zone: Case Study of Lubiatowo (Poland)

2015 ◽  
Vol 62 (1-2) ◽  
pp. 27-39 ◽  
Author(s):  
Grzegorz R. Cerkowniak ◽  
Rafał Ostrowski ◽  
Magdalena Stella
Keyword(s):  
Surf Zone ◽  
Shear Stresses ◽  
Research Station ◽  
Wave Parameters ◽  
Sea Bottom ◽  
Theoretical Investigations ◽  
Deep Water Wave ◽  
Offshore Wave ◽  
Wave Induced

AbstractThe paper presents results of field and theoretical investigations of a natural sandy shore located near the IBW PAN Coastal Research Station in Lubiatowo (Poland, the south Baltic Sea). The study site displays multi-bar cross-shore profiles that intensively dissipate wave energy, mostly by breaking. The main field data comprise offshore wave parameters and three cross-shore bathymetric profiles. Waveinduced nearbed velocities and bed shear stresses are theoretically modelled for weak, moderate, strong and extreme storm conditions to determine sediment motion regimes at various locations on the seaward boundary of the surf zone. The paper contains a discussion on the depth of closure concept, according to which the offshore range of sea bottom changes can be determined by the extreme seasonal deep-water wave parameters.

Bivariate description of offshore wave conditions with physics-based extreme value statistics

2004 ◽  
Vol 26 (3-4) ◽  
pp. 162-170 ◽  
Author(s):  
A. Repko ◽  
P.H.A.J.M. Van Gelder ◽  
H.G. Voortman ◽  
J.K. Vrijling
Keyword(s):  
Extreme Value ◽  
Extreme Value Statistics ◽  
Wave Conditions ◽  
Offshore Wave

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

2019 ◽  
Vol 7 (5) ◽  
pp. 139 ◽  
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.

scholarly journals Morphological coupling in multiple sandbar systems – a review

2014 ◽  
Vol 2 (1) ◽  
pp. 309-321 ◽  
Author(s):  
T. D. Price ◽  
B. G. Ruessink ◽  
B. Castelle
Keyword(s):  
Numerical Modelling ◽  
Data Model ◽  
High Energy ◽  
Finite Amplitude ◽  
Angle Of Incidence ◽  
Current State ◽  
Wave Conditions ◽  
Offshore Wave ◽  
Wave Incidence

Abstract. Subtidal sandbars often exhibit alongshore variable patterns, such as crescentic plan shapes and rip channels. While the initial formation of these patterns is reasonably well understood, the morphodynamic mechanisms underlying their subsequent finite-amplitude behaviour have been examined far less extensively. This behaviour concerns, among other aspects, the coupling of alongshore variable patterns in an inner bar to similar patterns in a more seaward bar, and the destruction of crescentic patterns. This review aims to present the current state of knowledge on the finite-amplitude behaviour of crescentic sandbars, with a focus on morphological coupling in double sandbar systems. In this context we include results from our recent study, based on a combination of remote-sensing observations, numerical modelling and data–model integration. Morphological coupling is an inherent property of double sandbar systems, where the inner bar may attain a type of morphology not found in single bar systems. Coupling is governed by water depth variability along the outer-bar crest and by various wave characteristics, including the offshore wave height and angle of incidence. In recent research, the role of the angle of wave incidence for sandbar morphodynamics has received more attention. Numerical modelling results have demonstrated that the angle of wave incidence is crucial to the flow pattern, sediment transport, and thus the emerging morphology of the coupled inner bar. Moreover, crescentic patterns predominantly vanish under high-angle wave conditions, highlighting the role of alongshore currents in straightening sandbars and challenging the traditional conception that crescentic patterns vanish under high-energy, erosive wave conditions only.

Offshore wave climate, Perth (Western Australia), 1994 - 96

1999 ◽  
Vol 50 (2) ◽  
pp. 95 ◽  
Author(s):  
A. J. Lemm ◽  
B. J. Hegge ◽  
G. Masselink
Keyword(s):  
Western Australia ◽  
Annual Variation ◽  
Wave Climate ◽  
Sea Breezes ◽  
Wave Data ◽  
Mean Wave Period ◽  
The Mean ◽  
Wave Conditions ◽  
Offshore Wave ◽  
Low Amplitude

The offshore wave climate of Perth (Western Australia) was analysed by using 2.5 years of non-directional 20-min wave data collected from March 1994 to August 1996. The mean wave conditions are characterized by a significant wave height (Hs) of 2.0 m and a spectral mean wave period (Tm) of 8.8 s. However, considerable annual variation in the wave conditions is experienced because of a distinct seasonality in the regional wind regime. During summer, daily sea breezes generate moderate seas (ambient Hs 1 to 2 m; Tm <8 s). During winter, frequent storms associated with mid-latitude depressions generate heavy seas and swell (ambient Hs 1.5 to 2.5 m; Tm >8 s). A low-amplitude background swell (Hs ~0.5 m), generated distantly in the Indian and Southern Oceans, is present all year round. Analysis of extreme wave conditions (Hs >4 m) indicates that, on average, 30 storms are experienced annually, and the storms are most frequent and intense during July. Estimates of extreme Hs, based on all available offshore wave data (12 years, 1975–96), for 1- and 100-year return periods, are 6.7 m and 9.8 m, respectively.

scholarly journals Fully nonlinear long-wave models in the presence of vorticity

2014 ◽  
Vol 759 ◽  
pp. 642-675 ◽  
Author(s):  
Angel Castro ◽  
David Lannes
Keyword(s):  
A Priori ◽  
Momentum Equation ◽  
Turbulence Theory ◽  
Two Dimensional ◽  
Rip Currents ◽  
Fully Nonlinear ◽  
Complex Interactions ◽  
Waves And Currents ◽  
Wave Models ◽  
The Waves

AbstractWe study here Green–Naghdi type equations (also called fully nonlinear Boussinesq, or Serre equations) modelling the propagation of large-amplitude waves in shallow water without a smallness assumption on the amplitude of the waves. The novelty here is that we allow for a general vorticity, thereby allowing complex interactions between surface waves and currents. We show that the a priori ($2+1$)-dimensional dynamics of the vorticity can be reduced to a finite cascade of two-dimensional equations. With a mechanism reminiscent of turbulence theory, vorticity effects contribute to the averaged momentum equation through a Reynolds-like tensor that can be determined by a cascade of equations. Closure is obtained at the precision of the model at the second order of this cascade. We also show how to reconstruct the velocity field in the ($2+1$)-dimensional fluid domain from this set of two-dimensional equations and exhibit transfer mechanisms between the horizontal and vertical components of the vorticity, thus opening perspectives for the study of rip currents, for instance.

scholarly journals A QGIS Plugin for Offshore Wave Hindcasting Based on Geographic Transposition of Wave Gauge Data

2016 ◽  
Vol 6 (2) ◽  
pp. 33-40
Author(s):  
F. Pasanisi ◽  
C. Tebano
Keyword(s):  
Southern Italy ◽  
Model Parameters ◽  
Output Data ◽  
Area Of Interest ◽  
Virtual Station ◽  
Gauge Data ◽  
Wave Hindcasting ◽  
Offshore Wave ◽  
Python Programming ◽  
Gauging Station

Abstract The paper presents a first experimental version of the original QGIS plugin QWaveTransposition that numerically implements the geographic transposition of wave gauge data method proposed by Contini and De Girolamo (1998) for offshore wave hindcasting. The method allows one to transfer wave data measured at a given gauging station to a virtual station located offshore the area of interest, by comparing the effective fetches at both stations. The QWaveTransposition plugin was implemented in Python programming language, including the NumPy package for numerical computations. A graphical user interface was developed to manage the input/output data and model parameters. The fetch geometry at real and virtual stations can be imported by selecting appropriate vector layers from the QGIS map. An application to a sample site in southern Italy is presented for example purposes.

Extreme waves induced by cyclone Nargis at Myanmar coast: numerical modeling versus satellite observations

2021 ◽  
Author(s):  
Thit Oo Kyaw ◽  
Miguel Esteban ◽  
Martin Mäll ◽  
Tomoya Shibayama
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Measurement Data ◽  
India Meteorological Department ◽  
High Energy ◽  
Significant Wave ◽  
Simulation Results ◽  
Wave Conditions ◽  
Offshore Wave ◽  
Cyclone Nargis

AbstractThe deltaic coast of Myanmar was severely hit by tropical cyclone Nargis in May 2008. In the present study, a top-down numerical simulation approach using the Weather Research and Forecasting (WRF) and Simulating WAves Nearshore (SWAN) models was conducted to study the meteorological and offshore wave characteristics of cyclone Nargis near the coast of Myanmar. The WRF simulation results agree well with the observed data from the India Meteorological Department. SWAN simulation results were compared with the WaveWatch 3 model by National Oceanic and Atmospheric Administration and validated against available measurement data from satellites. The model results show relatively good agreement, and hindcast with satellites data (significant wave height only) shows a correlation coefficient value of 0.89. The SWAN and satellite comparisons also show better fit for high wave conditions. The resulted maximum significant wave height of 7.3 m by SWAN is considerably higher in energy than the seasonal waves normally prevalent at Myanmar’s deltaic coast. The possibility of high energy waves due to cyclones should be considered during the design and operation of coastal and offshore projects in the area, particularly given the risks that climate change can intensify cyclones in the future. Since Myanmar lacks a dense network of in-situ observational stations, the methodology used in the current study presents the potential application of various numerical techniques and satellite data to estimate extreme wave conditions near the Myanmar coast.

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