WAVE KINEMATICS AND DIRECTIONALITY IN THE SURF ZONE

J. Van Heteren; M.J.F. Stive

doi:10.9753/icce.v19.5

WAVE KINEMATICS AND DIRECTIONALITY IN THE SURF ZONE

Coastal Engineering Proceedings ◽

10.9753/icce.v19.5 ◽

1984 ◽

Vol 1 (19) ◽

pp. 5 ◽

Cited By ~ 2

Author(s):

J. Van Heteren ◽

M.J.F. Stive

Keyword(s):

Linear Theory ◽

Linear Prediction ◽

Surf Zone ◽

Turbulent Energy ◽

Peak Frequency ◽

High Energy ◽

Radiation Stress ◽

Wave Kinematics ◽

Stress Prediction ◽

Quantitative Performance

Measurements of surface elevations and internal velocities have been conducted in a natural surf zone. The results were used to investigate the quantitative performance of linear theory in predicting the wave kinematics from the surface elevations. It appears that linear theory systematically overpredicts the horizontal velocities by 20 % in the frequency range around the peak, where the coherence with the surface motion is high, by 15 % at 2 times the peak frequency, changing in an underprediction of 15 % at higher frequencies. In these higher frequency ranges the rate of turbulent energy induced by breaking, contributes to the variance, so that the ratio of measured to theoretical r.m.s. fluctuation shows a trend of 25 % theoretical overprediction at negligible turbulent energy rates to 5 % underprediction at high turbulent energy rates. Furthermore the results were used to investigate the linear prediction of radiation stress and the effect of directionality on the radiation stress. Prediction of the radiation stress by unidirectional, linear theory gives an overestimation of 50 % at negligible turbulent energy rates to 35 % at high energy rates, which percentages reduce to 45 % and 25 i when the effect of shortcrestedness is taken into account.

Download Full-text

Faculty Opinions recommendation of Submarine Groundwater Discharge to a High-Energy Surf Zone at Stinson Beach, California, Estimated Using Radium Isotopes.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.8744956.9260054 ◽

2011 ◽

Author(s):

Russell Moll

Keyword(s):

Submarine Groundwater Discharge ◽

Surf Zone ◽

Groundwater Discharge ◽

High Energy ◽

Radium Isotopes ◽

Submarine Groundwater

Download Full-text

Environmental controls on surf zone injuries on high-energy beaches

Natural Hazards and Earth System Science ◽

10.5194/nhess-19-2183-2019 ◽

2019 ◽

Vol 19 (10) ◽

pp. 2183-2205 ◽

Cited By ~ 2

Author(s):

Bruno Castelle ◽

Tim Scott ◽

Rob Brander ◽

Jak McCarroll ◽

Arthur Robinet ◽

...

Keyword(s):

Wave Height ◽

Surf Zone ◽

High Tide ◽

High Energy ◽

Water Levels ◽

Small Scale ◽

Beach Morphology ◽

Environmental Controls ◽

Flow Activity ◽

Incident Waves

Abstract. The two primary causes of surf zone injuries (SZIs) worldwide, including fatal drowning and severe spinal injuries, are rip currents (rips) and shore-break waves. SZIs also result from surfing and bodyboarding activity. In this paper we address the primary environmental controls on SZIs along the high-energy meso–macro-tidal surf beach coast of southwestern France. A total of 2523 SZIs recorded by lifeguards over 186 sample days during the summers of 2007, 2009 and 2015 were combined with measured and/or hindcast weather, wave, tide, and beach morphology data. All SZIs occurred disproportionately on warm sunny days with low wind, likely because of increased beachgoer numbers and hazard exposure. Relationships were strongest for shore-break- and rip-related SZIs and weakest for surfing-related SZIs, the latter being also unaffected by tidal stage or range. Therefore, the analysis focused on bathers. More shore-break-related SZIs occur during shore-normal incident waves with average to below-average wave height (significant wave height, Hs = 0.75–1.5 m) and around higher water levels and large tide ranges when waves break on the steepest section of the beach. In contrast, more rip-related drownings occur near neap low tide, coinciding with maximised channel rip flow activity, under shore-normal incident waves with Hs >1.25 m and mean wave periods longer than 5 s. Additional drowning incidents occurred at spring high tide, presumably due to small-scale swash rips. The composite wave and tide parameters proposed by Scott et al. (2014) are key controlling factors determining SZI occurrence, although the risk ranges are not necessarily transferable to all sites. Summer beach and surf zone morphology is interannually highly variable, which is critical to SZI patterns. The upper beach slope can vary from 0.06 to 0.18 between summers, resulting in low and high shore-break-related SZIs, respectively. Summers with coast-wide highly (weakly) developed rip channels also result in widespread (scarce) rip-related drowning incidents. With life risk defined in terms of the number of people exposed to life threatening hazards at a beach, the ability of morphodynamic models to simulate primary beach morphology characteristics a few weeks or months in advance is therefore of paramount importance for predicting the primary surf zone life risks along this coast.

Download Full-text

FIELD MEASUREMENTS AND MODELLING OF NEARSHORE CURRENTS AT A HIGH-ENERGY GEOLOGICALLY-CONSTRAINED BEACH

Coastal Engineering Proceedings ◽

10.9753/icce.v36v.currents.18 ◽

2020 ◽

pp. 18

Author(s):

Arthur Mouragues ◽

Philippe Bonneton ◽

Bruno Castelle ◽

Vincent Marieu

Keyword(s):

Surf Zone ◽

Low Frequency ◽

Field Measurements ◽

High Energy ◽

Oblique Wave ◽

Wave Forcing ◽

Circulation Patterns ◽

Wave Conditions ◽

Nearshore Currents ◽

Set Up

We present field measurements of nearshore currents at a high-energy mesotidal beach with the presence of a 500-m headland and a submerged reef. Small changes in wave forcing and tide elevation were found to largely impact circulation patterns. In particular, under 4-m oblique wave conditions, our measurements indicate the presence of an intense low-frequency fluctuating deflection rip flowing against the headland and extending well beyond the surf zone. An XBeach model is further set up to hindcast such flow patterns.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/EiqnjBIkWJE

Download Full-text

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

Natural Hazards and Earth System Science ◽

10.5194/nhess-21-2075-2021 ◽

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.

Download Full-text

SURF BEAT GENERATION ON A MILD-SLOPE BEACH

Coastal Engineering Proceedings ◽

10.9753/icce.v21.79 ◽

1988 ◽

Vol 1 (21) ◽

pp. 79 ◽

Cited By ~ 10

Author(s):

Hemming A. Schaffer ◽

Ib A. Svendsen

Keyword(s):

Surf Zone ◽

Beat Generation ◽

Radiation Stress ◽

Inhomogeneous Wave ◽

Wave Groups ◽

Forcing Function ◽

Long Wave ◽

Inhomogeneous Wave Equation ◽

Slope Beach ◽

Resonant Generation

Two dimensional generation of surf beats by incident wave groups is examined theoretically. An inhomogeneous wave equation describes the amplitude of the surf beat wave. The forcing function is the modulation of the radiation stress. The short waves are amplitude modulated both outside and inside the surf zone causing the long wave generation to continue right to the shore line. Resonant generation as shallow water is approached is included. The analytical solution is evaluated numerically and shows a highly complicated amplitude variation of the surf beat depending on the parameters of the problem.

Download Full-text

A NuSTAR view of powerful γ-ray loud blazars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935750 ◽

2019 ◽

Vol 627 ◽

pp. A72 ◽

Cited By ~ 2

Author(s):

G. Ghisellini ◽

M. Perri ◽

L. Costamante ◽

G. Tagliaferri ◽

T. Sbarrato ◽

...

Keyword(s):

Energy Distribution ◽

Spectral Energy Distribution ◽

Peak Frequency ◽

High Energy ◽

Spectral Energy ◽

X Rays ◽

X Ray ◽

Γ Ray ◽

The Universe ◽

Jet Power

We observed three blazars at z > 2 with the NuSTAR satellite. These were detected in the γ-rays by Fermi/LAT and in the soft X-rays, but have not yet been observed above 10 keV. The flux and slope of their X-ray continuum, together with Fermi/LAT data allows us to estimate their total electromagnetic output and peak frequency. For some of them we were able to study the source in different states, and investigate the main cause of the different observed spectral energy distribution. We then collected all blazars at redshifts greater than 2 observed by NuSTAR, and confirm that these hard and luminous X-ray blazars are among the most powerful persistent sources in the Universe. We confirm the relation between the jet power and the disk luminosity, extending it at the high-energy end.

Download Full-text

Structure and Microwave Absorption Properties of Ho-Fe-Si Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.914.117 ◽

2018 ◽

Vol 914 ◽

pp. 117-123 ◽

Cited By ~ 1

Author(s):

Jia Liang Luo ◽

Shun Kang Pan ◽

Li Chun Cheng ◽

Pei Hao Lin ◽

Yu He ◽

...

Keyword(s):

Ball Milling ◽

Matching Condition ◽

Peak Frequency ◽

High Energy ◽

X Ray Diffraction ◽

Absorption Properties ◽

Arc Melting ◽

Microwave Absorbing Materials ◽

Milling Method ◽

Si Content

The Ho2Fe17-xSix (x=0.0, 0.1, 0.2, 0.3) alloys were prepared by arc melting and high energy ball milling method. The influence of the Si substitution on phase structure, morphology and electromagnetic parameters were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vector network analyzer (VNA), respectively. The results show that the Ho-Fe-Si particles are flaky after the ball milling. The minimum absorption peak frequency shifts towards a lower frequency region with the increasing of Si content. The minimum RL of Ho2Fe16.7Si0.3 reaches-42.96 dB at 9.76 GHz, and the frequency bandwidth of R<-10 dB reaches about 2.64 GHz with the best matching condition d=1.6 mm. The reflection loss with the thickness ranging of 1.2-3.0 mm could reach-10 dB, which indicates the particles be considered as the promising microwave absorbing materials with a good absorption properties.

Download Full-text

MODELING SPILLED OIL PARTITIONING IN NEARSHORE AND SURF ZONE AREAS

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-1985-1-379 ◽

1985 ◽

Vol 1985 (1) ◽

pp. 379-383 ◽

Cited By ~ 4

Author(s):

Erich R. Gundlach ◽

Timothy W. Kana ◽

Paul D. Boehm

Keyword(s):

Wave Energy ◽

Surf Zone ◽

High Energy ◽

Sandy Beaches ◽

Coarse Grained ◽

Tidal Range ◽

Incoming Wave ◽

Fine Grained ◽

Beach Sediments ◽

Rocky Coasts

ABSTRACT The shoreline of a potential spill impact area can be divided into units, each with a specific geomorphology. As oil enters each unit, it will (to varying extents) evaporate, dissolve, interact with suspended particles and sink, biodegrade, photo-oxidize, be transported to the next unit, or strand on the shoreline. In the last case, oil will reenter the aquatic system after a given time and again be exposed to these same processes. For modeling purposes, the world's shorelines can be divided into sedimentary beaches and tectonic rocky coasts, varying in wave energy and tidal range. The size of beach sediments can range from very coarse grained (gravels) to very fine grained (silts and clays). Coarse-grained shorelines have higher incoming wave energy than fine-grained areas. Along all coasts, several partitioning components remain relatively constant for medium to light crude oils, e.g., evaporation (30 to 50 percent) and biodegradation/photo-oxidation (0 to 5 percent). Others may vary substantially. For instance, sedimentation may reach 10 to 20 percent in fine-grained estuaries, but only 0 to 2 percent along high energy coasts having very coarse-grained bottom sediments. Similarly, along sandy beaches the stranding of oil along the shoreline may reach 25 to 35 percent, as compared to only 1 to 2 percent along steep, rocky coasts. Dissolution, in general, does not vary so radically, being approximately 10 to 15 percent along high-energy rocky coasts, as compared to 5 to 10 percent in sheltered estuaries that do not have the mixing energy to drive additional oil into the water column.

Download Full-text