scholarly journals Environmental controls on surf zone injuries on high-energy beaches

2019 ◽  
Vol 19 (10) ◽  
pp. 2183-2205 ◽  
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.

scholarly journals Environmental controls on surf zone injuries on high-energy beaches

2019 ◽  
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 body boarding activity. In this paper we address the primary environmental controls on SZIs along the high-energy meso-macrotidal surf beach coast of SW 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 focussed on bathers. Shore-break related SZIs disproportionately 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 range when waves break on the steepest section of the beach. In contrast, rip related drownings occur disproportionally near neap low tide, coinciding with maximized channel rip flow activity, under shore-normal incident waves with Hs > 1.25 m and periods mean wave period 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 highly interannually 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/months in advance is therefore of paramount importance to predict the primary surf-zone life risks along this coast.

scholarly journals EFFECTS OF TIDE ON WAVES IN THE OUTER SEINE ESTUARY AND THE HARBOR OF LE HAVRE

2012 ◽  
Vol 1 (33) ◽  
pp. 47
Author(s):  
Nicolas Guillou ◽  
Georges Chapalain
Keyword(s):  
Wave Height ◽  
High Tide ◽  
Numerical Procedure ◽  
Water Levels ◽  
Seine Estuary ◽  
Topographic Features ◽  
Southern Central ◽  
Spatio Temporal ◽  
Ambient Currents ◽  
Induced Changes

The present study examines the influences of time-varying tide-induced water depths and currents on waves in the outer Seine estuary (southern central English Channel) and their penetration in the harbor of Le Havre and its new infrastructures Port 2000. The investigation is based on a numerical procedure which links regional phase-averaged wave modules with a local phase-resolving wave module within Port 2000 harbor. Required spatio-temporal evolutions of tidal free-surface elevation and current are computed by circulation modules. Numerical results of wave height are compared with field data collected at three wave buoys in the access harbor channel and its inner basin. Predictions exhibit a local increase (up to 30 %) of wave height induced by current refraction at slack tide in the access harbor channel. Respective mappings of the wave height modified by the tide, the water levels alone and the currents alone confirm this finding. The effect of currents on waves are pronounced along the southern breakwater of Port 2000 harbor and in the vicinity of coastal topographic features of the outer Seine estuary. Ultimate predictions of wave propagation within Port 2000 basin exhibit, however, the negligible direct influence of local ambient currents on wave height. Observed-semidiurnal wave-height variations in the inner basin are thus mainly associated with the propagation of the outer tide-induced modulation. Mappings of maximum wave-height within harbor basin reveal an increased exposition of the northern wharves at high tide and the southern western breakwater at low tide in relation to current-induced changes in the approaching-waves direction.

scholarly journals 2D OVERTOPPING AND IMPACT EXPERIMENTS IN SHALLOW FORESHORE CONDITIONS

2018 ◽  
pp. 67
Author(s):  
Vincent Gruwez ◽  
Ine Vandebeek ◽  
Dogan Kisacik ◽  
Maximilian Streicher ◽  
Corrado Altomare ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Surf Zone ◽  
High Spatial Resolution ◽  
Wave Structure ◽  
High Energy ◽  
Water Levels ◽  
Wave Transformation ◽  
Wave Overtopping ◽  
Typical Situation ◽  
Wave Flume

This paper introduces the 2D experiments conducted for the CREST project in the wave flume of Ghent University. The experiments focus on wave interactions with low-crested sea dikes fronted by a shallow foreshore and mildly to steeply sloping beaches, which is a very typical situation along the Belgian coast. Foreshore slopes of 1/20, 1/35, 1/50 and 1/80 were tested for a range of low to high energy wave conditions, a variation in wave steepness and two water levels. The main goal was to obtain a dataset in which the effects of the infragravity waves on the wave-structure interactions (i.e. wave overtopping and impact forces) can be studied. The tests included high spatial resolution surface elevation measurement tests, which is new for beaches including a dike in the inner surf zone. From the first results it became clear that the foreshore slope influences the wave transformation up to the dike toe. The influence is apparent comparing to existing (semi-) empirical models for prediction of the spectral wave period at the dike toe and wave overtopping at the dike crest. The high spatial resolution data show a steep increase in infragravity significant wave height in the very shallow area in front of the dike.

The Establishment of Wave Model in Qingdao Fushan Bay

2010 ◽  
Vol 156-157 ◽  
pp. 1181-1186
Author(s):  
Shui Yu Li
Keyword(s):  
Boundary Conditions ◽  
Wave Height ◽  
Return Period ◽  
Wave Energy ◽  
Wave Model ◽  
Energy Generation ◽  
Water Levels ◽  
Rectangular Grid ◽  
Generation Planning ◽  
Incident Waves

A wave model in Qingdao Fushan Bay is established in the paper. The effect of the variety of terrain, dredging in the basin, the shelter of the structure, the reflection of the piers and breakwaters are taken into account. Rectangular grid is applied in the calculation. For reducing the errors and ensuring the precision, normally incident waves and completely-absorbed boundary conditions are considered in the calculation. The result gives the wave height at each point in different water levels, and wave directions of 50-years return period, which provides a basis for the shoreline structure of wave energy generation planning and designing.

scholarly journals Intertidal finger bars at El Puntal, Bay of Santander, Spain: observation and forcing analysis

2014 ◽  
Vol 2 (1) ◽  
pp. 349-361 ◽  
Author(s):  
E. Pellón ◽  
R. Garnier ◽  
R. Medina
Keyword(s):  
Surf Zone ◽  
High Tide ◽  
Small Scale ◽  
Sand Transport ◽  
Maximum Speed ◽  
Northern Coast ◽  
Astronomical Tide ◽  
Transport Direction ◽  
Waves And Currents ◽  
Main Candidate

Abstract. A system of 15 small-scale finger bars has been observed, by using video imagery, between 23 June 2008 and 2 June 2010. The bar system is located in the intertidal zone of the swell-protected beaches of El Puntal Spit, in the Bay of Santander (northern coast of Spain). The bars appear on a planar beach (slope = 0.015) with fine, uniform sand (D50 = 0.27 mm) and extend 600 m alongshore. The cross-shore span of the bars is determined by the tidal horizontal excursion (between 70 and 130 m). They have an oblique orientation with respect to the low-tide shoreline; specifically, they are down-current-oriented with respect to the dominant sand transport computed (mean angle of 26° from the shore normal). Their mean wavelength is 26 m and their amplitude varies between 10 and 20 cm. The full system slowly migrates to the east (sand transport direction) with a mean speed of 0.06 m day-1, a maximum speed in winter (up to 0.15 m day-1) and a minimum speed in summer. An episode of merging has been identified as bars with larger wavelength seem to migrate more slowly than shorter bars. The wind blows predominantly from the west, generating waves that transport sediment across the bars during high-tide periods. This is the main candidate to explain the eastward migration of the system. In particular, the wind can generate waves of up to 20 cm (root-mean-squared wave height) over a fetch that can reach 4.5 km at high tide. The astronomical tide seems to be important in the bar dynamics, as the tidal level changes the fetch and also determines the time of exposure of the bars to the surf-zone waves and currents. Furthermore, the river discharge could act as input of suspended sediment in the bar system and play a role in the bar dynamics.

scholarly journals Field Measurements of a High-Energy Headland Deflection Rip Current: Tidal Modulation, Very Low Frequency Pulsation and Vertical Structure

2020 ◽  
Vol 8 (7) ◽  
pp. 534 ◽  
Author(s):  
Damien Sous ◽  
Bruno Castelle ◽  
Arthur Mouragues ◽  
Philippe Bonneton
Keyword(s):  
Wave Height ◽  
Surf Zone ◽  
Low Frequency ◽  
High Energy ◽  
Winter Period ◽  
Breaking Wave ◽  
Driving Mechanism ◽  
Peak Period ◽  
Very Low Frequency ◽  
Wave Incidence

Headland rips, sometimes referred to as boundary rips, are rip currents flowing against natural or artificial obstructions extending seaward from the beach, such as headland or groynes. They can be driven either by the deflection of the longshore current against the obstacle or by alongshore variation in breaking wave height due to wave shadowing in the lee of the obstacle. The driving mechanism therefore essentially depends on the angle of wave incidence with respect to the natural or artificial obstruction. We analyze 42 days of velocity profile measurements against a natural headland at the high-energy meso-macrotidal beach of Anglet, southwest France. Measurements were collected in 6.5–10.5-m depth as tide elevation varied, during the autumn–winter period with offshore significant wave height and period ranging 0.9–6 m and 8–16 s, respectively, and the angle of wave incidence ranging from −20 ∘ to 20 ∘ . Here we analyze deflection rip configurations, corresponding to approximately 24 days of measurements, for which the current meter was alternatively located in the rip neck, rip head or away from the rip as wave and tide conditions changed. Deflection rips were associated with large offshore-directed velocities (up to 0.6 m/s depth-averaged velocities) and tide modulation for low- to moderate-energy waves. The vertical profile of deflection rips was found to vary from depth-uniform in the rip neck to strongly depth-varying further offshore in the rip head with maximum velocities near the surface. Very low frequency motions of the rip were dramatic, ranging 10–60 min with a dominant peak period of approximately 40 min, i.e., with longer periods than commonly reported. The strong offshore-directed velocities measured well beyond the surf zone edge provide new insight into deflection rips as a dominant mechanism for water and sediment exchanges between embayed (or structurally-controlled) beaches and the inner-shelf and/or the adjacent embayments.

Longshore variations in longshore currents

1977 ◽  
Vol 14 (8) ◽  
pp. 1897-1905 ◽  
Author(s):  
J. R. Keeley ◽  
A. J. Bowen
Keyword(s):  
Wave Height ◽  
Large Scale ◽  
Surf Zone ◽  
Small Scale ◽  
Angle Of Incidence ◽  
Wave Direction ◽  
Incoming Wave ◽  
Wave Refraction ◽  
Longshore Currents ◽  
Deep Water Wave

The mean longshore currents in the surf zone were measured along more than 1 km of a beach. These measurements were compared to a theoretical model of the system in which the current depends on the angle of incidence of the incoming waves and the longshore variation in both wave height and breaker angle. A wave refraction programme was used to compute the values of wave height and breaker angle every 100 m along the beach from the measured values of wave period and deep water wave direction. In general, the large scale variation of currents along the beach was well described by the theory. However, superimposed upon these large scales of motion were fairly regular, small-scale circulation cells which are probably associated with edge waves at the incoming wave frequency.

scholarly journals Learning in the Anthropocene

2021 ◽  
Vol 10 (6) ◽  
pp. 233
Author(s):  
Rasmus Karlsson
Keyword(s):  
Renewable Energy Sources ◽  
Local Level ◽  
High Energy ◽  
Small Scale ◽  
Optical Illusions ◽  
Global Trends ◽  
Energy Technologies ◽  
Climate Action ◽  
Enlightenment Project ◽  
Global Trajectory

While the precautionary principle may have offered a sound basis for managing environmental risk in the Holocene, the depth and width of the Anthropocene have made precaution increasingly untenable. Not only have many ecosystems already been damaged beyond natural recovery, achieving a sustainable long-term global trajectory now seem to require ever greater measures of proactionary risk-taking, in particular in relation to the growing need for climate engineering. At the same time, different optical illusions, arising from temporary emissions reductions due to the COVID-19 epidemic and the local deployment of seemingly “green” small-scale renewable energy sources, tend to obscure worsening global trends and reinforce political disinterest in developing high-energy technologies that would be more compatible with universal human development and worldwide ecological restoration. Yet, given the lack of feedback between the global and the local level, not to mention the role of culture and values in shaping perceptions of “sustainability”, the necessary learning may end up being both epistemologically and politically difficult. This paper explores the problem of finding indicators suitable for measuring progress towards meaningful climate action and the restoration of an ecologically vibrant planet. It is suggested that such indicators are essentially political as they reflect, not only different assessments of technological feasibility, but orientations towards the Enlightenment project.

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