Surf zone eddies coupled with rip current morphology

2004 ◽  
Vol 109 (C7) ◽  
Author(s):  
Jamie H. MacMahan
Keyword(s):  
Surf Zone ◽  
Rip Current

scholarly journals A Bayesian network approach to modelling rip-current drownings and shore-break wave injuries

2021 ◽  
Vol 21 (7) ◽  
pp. 2075-2091
Author(s):  
Elias de Korte ◽  
Bruno Castelle ◽  
Eric Tellier
Keyword(s):  
Bayesian Network ◽  
Environmental Conditions ◽  
Surf Zone ◽  
High Energy ◽  
Environmental Data ◽  
Tidal Range ◽  
Boreal Summer ◽  
Rip Current ◽  
Rip Currents ◽  
Awareness Campaigns

Abstract. A Bayesian network (BN) approach is used to model and predict shore-break-related injuries and rip-current drowning incidents based on detailed environmental conditions (wave, tide, weather, beach morphology) on the high-energy Gironde coast, southwest France. Six years (2011–2017) of boreal summer (15 June–15 September) surf zone injuries (SZIs) were analysed, comprising 442 (fatal and non-fatal) drownings caused by rip currents and 715 injuries caused by shore-break waves. Environmental conditions at the time of the SZIs were used to train two separate Bayesian networks (BNs), one for rip-current drownings and the other one for shore-break wave injuries. Each BN included two so-called “hidden” exposure and hazard variables, which are not observed yet interact with several of the observed (environmental) variables, which in turn limit the number of BN edges. Both BNs were tested for varying complexity using K-fold cross-validation based on multiple performance metrics. Results show a poor to fair predictive ability of the models according to the different metrics. Shore-break-related injuries appear more predictable than rip-current drowning incidents using the selected predictors within a BN, as the shore-break BN systematically performed better than the rip-current BN. Sensitivity and scenario analyses were performed to address the influence of environmental data variables and their interactions on exposure, hazard and resulting life risk. Most of our findings are in line with earlier SZI and physical hazard-based work; that is, more SZIs are observed for warm sunny days with light winds; long-period waves, with specifically more shore-break-related injuries at high tide and for steep beach profiles; and more rip-current drownings near low tide with near-shore-normal wave incidence and strongly alongshore non-uniform surf zone morphology. The BNs also provided fresh insight, showing that rip-current drowning risk is approximately equally distributed between exposure (variance reduction Vr=14.4 %) and hazard (Vr=17.4 %), while exposure of water user to shore-break waves is much more important (Vr=23.5 %) than the hazard (Vr=10.9 %). Large surf is found to decrease beachgoer exposure to shore-break hazard, while this is not observed for rip currents. Rapid change in tide elevation during days with large tidal range was also found to result in more drowning incidents. We advocate that such BNs, providing a better understanding of hazard, exposure and life risk, can be developed to improve public safety awareness campaigns, in parallel with the development of more skilful risk predictors to anticipate high-life-risk days.

scholarly journals Occurrence features of Rip current at Ha My (Dien Ban district) and Tam Thanh (Tam Ky city) beaches, Quang Nam province

2019 ◽  
Vol 19 (4A) ◽  
pp. 43-53
Author(s):  
Le Dinh Mau ◽  
Nguyen Van Tuan ◽  
Nguyen Chi Cong ◽  
Tran Van Binh ◽  
Pham Ba Trung ◽  
...  
Keyword(s):  
Wave Energy ◽  
Surf Zone ◽  
Transition Period ◽  
Current System ◽  
Southwest Monsoon ◽  
Northeast Monsoon ◽  
Rip Current ◽  
Rip Currents ◽  
Open Sea ◽  
Study Results

Rip current is a relatively strong, narrow current flowing outward from the beach through the surf zone and presenting a hazard to swimmers. This paper presents some occurrence features of Rip current at main swimming beaches in Quang Nam province, Central Vietnam. Study results show that most of swimming beaches along Quang Nam province coast are directly opposed to open sea and strongly affected by swell. Therefore, Rip current system can occur at any time in the year with large dimension and intensity. During Northeast monsoon (November to March) beach morphology is considerably changed by strong wave action, thus the strongest rip current is formed. However, in this period careful swimmers can easily identify where that rip current occurs along the beach. During the transition period from Northeast monsoon to Southwest monsoon (April to May) wave energy is reduced, thus Rip current intensity is also decreased. During Southwest monsoon (June to August) wave energy is not strong and beach is accreted, therefore some Rip currents remain at reasonable morphology places along the beach. During the transition period from Southwest monsoon to Northeast monsoon (September to October) Rip current can occur at deep places along the beach with characteristics of narrow dimension, thus causing more danger to swimmer. Especially, dangerous rip current is caused by swell which comes from active region of tropical cyclone in open sea. In this period wave field in the nearshore region is not rough, thus most of swimmers are not cautious when swimming at dangerous rip current places.

scholarly journals Sea Surface Temperature Variability at the Scripps Institution of Oceanography Pier*

2014 ◽  
Vol 44 (11) ◽  
pp. 2877-2892 ◽  
Author(s):  
David M. Checkley ◽  
Martin Lindegren
Keyword(s):  
Time Series ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Surf Zone ◽  
Rate Of Change ◽  
Sea Surface ◽  
Past Century ◽  
Current Transport ◽  
Rip Current ◽  
Scripps Institution

Abstract Sea surface temperature (SST) has been measured from near the end of the Scripps Institution of Oceanography (SIO) pier daily since 1916. It is one of the world’s longest instrumental time series of SST. It is widely used in studies of climate and marine ecosystems and in fisheries management. The authors hypothesized that a discontinuity exists in 1988, when the old pier was replaced with the present pier. A regression of annual-mean SST at SIO (SSTSIO) on the Pacific decadal oscillation index for 1916–87 was used to predict annual-mean SST (SSTSIO, PDO) for 1916–present. The residual (ResSSTSIO = SSTSIO − SSTSIO,PDO) time series shows a positive discontinuity in 1988, when the present SIO pier was first used to measure SSTSIO. No discontinuity in 1988 was observed for ResSST at 12 other shore stations or in nearby waters. Use of the first principal component of other shore station time series of annual-mean SST as the predictor yields similar results. SSTSIO measured over 3 days shows a diel cycle and short-term variability consistent with rip current transport of warm surf-zone water to the end of the SIO pier. This study hypothesizes that rip current transport increased with the change from the old to the present pier and contributed to the observed discontinuity in SIO pier SST. The authors estimate an artifact of about +0.45°C due to both rapid (1988 pier change) and gradual processes. Adjusting the SIO pier SST time series for this artifact reduces the long-term trend from +1.1° to +0.6°C century−1, consistent with the global rate of change of SST over the past century.

scholarly journals RIP CURRENT SPACING AS AN EIGENVALUE

1978 ◽  
Vol 1 (16) ◽  
pp. 47
Author(s):  
Noriyuki Iwata
Keyword(s):  
Conservation Laws ◽  
Surf Zone ◽  
Coastal Region ◽  
Normal Incidence ◽  
Wave Action ◽  
Rip Current ◽  
Radiation Stress ◽  
Matching Conditions ◽  
Horizontal Mixing ◽  
The Waves

Mass, momentum and wave action conservation laws, including the radiation stress, are used to obtain a rip current spacing as an eigenvalue. A coastal region is divided into two parts: offshore region and surf zone separated by a breaker line. Only the case of normal incidence of the waves is considered. From the matching conditions of the two horizontal velocity components at the breaker line, we can obtain rip current spacing as a function of a nondimensional parameter characterizing the surf zone, for an arbitrary value of a parameter indicating the strength of horizontal mixing.

scholarly journals Analisa Model Matematik Arus Sejajar Pantai Pada Groin Seri Permeable

2018 ◽  
Vol 19 (2) ◽  
pp. 113
Author(s):  
Adi Surya Pria Pranata ◽  
Novi Andhi Setyo Purwono ◽  
Ary Sismiani
Keyword(s):  
Current Velocity ◽  
Physical Modeling ◽  
Surf Zone ◽  
Rip Current ◽  
Longshore Current ◽  
Long Distance ◽  
Direction Of Movement ◽  
The Mathematical Model ◽  
Additional Reduction

This research is the mathematical model has been made with two groins, permeable and impermeable groins, with the variation is in length and distance; 50 meters, 100 meters, 150 meters and 200 meters. A modelling has been done by using the data of physical modeling study by Chen., et al, 2003, and used as input to the simulation of mathematical models using 2D Boussinesq software.Results of the research showed the influence of variation model long distance between the groins, the reduction of longshore current velocity along the coast with an average 59.21% reduction for the double permeable groin with 50 meters long, 76.02% for 100 meters, 79.50% for 150 meters, 80.49% for 200 meters. The reduction of longshore current velocity along the coast are 57.42% for an impermeable groin groin double with 50 meters, 84.61% for 100 meters, 150% for 88.89 meters, and 89.91% for 200 meters. The distance variation between one groin to the other groin has a result that a longer permeable or impermeable groin affects the reduction longshore current velocity along the coast of the Surf Zone with the addition of longshore current velocity reduction occurs along the coast up to 20%. Reduction of longshore current velocity along the coast by the permeable and impermeable groin Permeable and impermeable groins has not been significantly occured in the long-term groin area exceeding Surf zone with an average additional reduction up to 5%. The longshore current velocity approaching the speed of currents along the coast for the existing conditions at a distance up to 2.4 times of length of groins. And the distance between the groins are too close if we compare to the long groins causing the current direction of movement towards the sea (rip Current). 

scholarly journals NEARSHORE CURRENTS ON A PARTIALLY ROCKY SHORE

1980 ◽  
Vol 1 (17) ◽  
pp. 65
Author(s):  
T.O. Sasaki ◽  
H. Igarashi ◽  
S. Harikai
Keyword(s):  
Rocky Shore ◽  
Surf Zone ◽  
High Energy ◽  
Sandy Beaches ◽  
Physical Experiment ◽  
Low Energy ◽  
Rip Current ◽  
Rip Currents ◽  
Wave Regime ◽  
Wave Refraction

Nearshore circulation on a partially rocky shore at Haranomachi Beach, Fukushima Prefecture, Japan has been studied in terms of field observations and numerical experiments for a low energy wave regime and with a physical experiment for a high energy wave regime. No significant distinctions were found in current velocity and rip current spacing between rocky and sandy beaches for the low energy wave regime, however the positions of rip currents were affected by wave refraction from the offshore exposed rocky bottom. On the other hand, since the surf zone bed is largely occupied by an exposed rocky floor for the high energy wave regime, the circulation exhibited fairly irregular patterns, so that a rip current becomes difficult to define, however the positions of inflow across the breaker line were found to be coincident with wave convergence zone.

scholarly journals EFFECT OF RIP CURRENT BARRIER ON HARBOR SHOALING

1984 ◽  
Vol 1 (19) ◽  
pp. 140 ◽  
Author(s):  
Tamio O. Sasaki ◽  
Hiroshi Sakuramoto
Keyword(s):  
Surf Zone ◽  
Cost Effective ◽  
High Energy ◽  
Rip Current ◽  
Rip Currents ◽  
Effective Measure ◽  
The Pacific ◽  
Small Craft ◽  
The Pacific Ocean ◽  
Cost Effective Measure

Prototype experiments on rip currents and sediment transport around structures were conducted at two fishery harbors on microtidal high energy beaches facing the Pacific Ocean. The purpose of the experiments was to examine the performance and mechanism of rip current barrier structures on harbor shoaling. Based on the results of five experiments, the wave breaker heights during which varied from 1.1 m to 3.0 m, it is concluded that shore-parallel rip current barriers are effective if their length is greater than the surf zone width and if they are located outside the surf zone. When the above conditions are satisfied, the rip current barrier is a cost-effective measure against shoaling of small craft harbors.

scholarly journals A GPS-Tracked Surf Zone Drifter*

2003 ◽  
Vol 20 (7) ◽  
pp. 1069-1075 ◽  
Author(s):  
W. E. Schmidt ◽  
B. T. Woodward ◽  
K. S. Millikan ◽  
R. T. Guza ◽  
B. Raubenheimer ◽  
...  
Keyword(s):  
Real Time ◽  
Global Positioning System ◽  
Water Depth ◽  
Surf Zone ◽  
Radio Link ◽  
Positioning System ◽  
Rip Current ◽  
Global Positioning

Abstract A drifter designed to measure surf zone circulation has been developed and field tested. Drifter positions accurate to within a few meters are estimated in real time at 0.1 Hz using the global positioning system (GPS) and a shore-to-drifter radio link. More accurate positions are estimated at 1 Hz from postprocessed, internally logged data. Mean alongshore currents estimated from trajectories of the 0.5-m-draft drifters in 1–2-m water depth agree well with measurements obtained with nearby, bottom-mounted, acoustic current meters. Drifters deployed near the base of a well-developed rip current often followed eddylike paths within the surf zone before being transported seaward.

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