Longshore variation in coastal foredune growth on a megatidal beach from UAV measurements

2020 ◽  
Author(s):  
Iain Fairley ◽  
Jose Horrillo-Caraballo ◽  
Anouska Mendzil ◽  
Georgie Blow ◽  
Henry Miller ◽  
...  
Keyword(s):  
Wave Energy ◽  
Point Cloud ◽  
High Tide ◽  
Tidal Range ◽  
Dune System ◽  
Wave Heights ◽  
Upper Intertidal ◽  
Rtk Gps ◽  
Swansea Bay ◽  
Dune Area

<p>Coastal dunes are both a vital natural coastal defence and a key ecological habitat; therefore, understanding their evolution is important to inform coastal management. Megatidal environments are the world largest tidal ranges and hence provide a unique endmember of the tidal range continuum. A study site at Crymlyn Burrows, Swansea Bay, UK is monitored here; the area was originally of applied interest due to its identification as a key receptor of the Swansea Bay Tidal Lagoon project. The study site comprises of 2km of dune frontage bounded to the west by hard sea defences and to the east by the River Neath estuary. The intertidal is characterized by a shallow slope and crescentic intertidal bars. Mean spring tidal range at the nearby Mumbles tide gauge is 8.46m; mean wave heights at a wave buoy offshore of the site (depth 9m LAT) are 0.66m and storm wave heights exceed 3m; predominant wind direction is in an alongshore – onshore direction.</p><p>A Sensefly Ebee-RTK drone with a Sony RGB camera has been used to map the dune system and the mid to upper intertidal beach on a monthly – bimonthly frequency since October 2018. Initial post-processing was conducted in the Sensefly Emotion3 software; Pix4D was then used to generate a point cloud from the georeferenced images. RTK-GPS surveyed ground control points distributed over the study area were used to improve the accuracy of the solution. Point clouds were cleaned to remove noise using Cloud Compare, an open source point cloud editor, before being interpolated onto a gridded surface. Comparison of the gridded surface against RTK-GPS surveyed points gave a vertical mean absolute error (MAE) of 0.05m over the beach area. Comparison in the dune area is more complex since the raw point cloud includes the vegetation and hence over-estimates height compared to the bare earth. Based on the raw point cloud, MAE over the dune area was 0.22m; however, when vegetation points were removed using artificial neural network based colour discrimination, the MAE was 0.05m.</p><p>Longshore variation in dune evolution is clearly evident. At the eastern and western ends of the dune system, dune progradation can be observed whereas in the central portion the frontal dune is cliffed and the dune foot position is static or eroding landward. Pressure transducers have been deployed in a longshore array at the neap high tide level to assess variation in wave energy reaching the upper intertidal over the study area.</p><p>This presentation will explore whether this variation in behavior is due to longshore variation in wave energy (erosion potential), variation in sediment availability (accretion potential) or the persistence of antecedent morphology.</p>

scholarly journals Spatial Variation in Coastal Dune Evolution in a High Tidal Range Environment

2020 ◽  
Vol 12 (22) ◽  
pp. 3689
Author(s):  
Iain Fairley ◽  
Jose Horrillo-Caraballo ◽  
Ian Masters ◽  
Harshinie Karunarathna ◽  
Dominic E. Reeve
Keyword(s):  
Spatial Scales ◽  
Coastal Dunes ◽  
Sediment Supply ◽  
Tidal Range ◽  
Coastal Protection ◽  
Dune System ◽  
Pressure Transducers ◽  
Significant Wave ◽  
Wave Heights ◽  
Significant Wave Heights

Coastal dunes have global importance as ecological habitats, recreational areas, and vital natural coastal protection. Dunes evolve due to variations in the supply and removal of sediment via both wind and waves, and on stabilization through vegetation colonization and growth. One aspect of dune evolution that is poorly understood is the longshore variation in dune response to morphodynamic forcing, which can occur over small spatial scales. In this paper, a fixed wing unmanned aerial vehicle (UAV), is used to measure the longshore variation in evolution of a dune system in a megatidal environment. Dune sections to the east and west of the study site are prograding whereas the central portion is static or eroding. The measured variation in dune response is compared to mesoscale intertidal bar migration and short-term measurements of longshore variation in wave characteristics during two storms. Intertidal sand bar migration is measured using satellite imagery: crescentic intertidal bars are present in front of the accreting portion of the beach to the west and migrate onshore at a rate of 0.1–0.2 m/day; episodically the eastern end of the bar detaches from the main bar and migrates eastward to attach near the eastern end of the study area; bypassing the central eroding section. Statistically significant longshore variation in intertidal wave heights were measured using beachface mounted pressure transducers: the largest significant wave heights are found in front of the dune section suffering erosion. Spectral differences were noted with more narrow-banded spectra in this area but differences are not statistically significant. These observations demonstrate the importance of three-dimensionality in intertidal beach morphology on longshore variation in dune evolution; both through longshore variation in onshore sediment supply and through causing longshore variation in near-dune significant wave heights.

scholarly journals Optimising the Operation of Tidal Range Schemes

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2870 ◽  
Author(s):  
Jingjing Xue ◽  
Reza Ahmadian ◽  
Roger Falconer
Keyword(s):  
Renewable Energy ◽  
Energy Demand ◽  
Maximum Energy ◽  
Energy Output ◽  
Tidal Range ◽  
Marine Renewable Energy ◽  
Modelling Methodology ◽  
Similar Operation ◽  
Swansea Bay ◽  
The Uk

Marine renewable energy, including tidal renewable energy, is one of the less exploited sources of energy that could contribute to energy demand, while reducing greenhouse gas emissions. Amongst several proposals to build tidal range structure (TRS), a tidal lagoon has been proposed for construction in Swansea Bay, in the South West of the UK, but this scheme was recently rejected by the UK government due to the high electricity costs. This decision makes the optimisation of such schemes more important for the future. This study proposes various novel approaches by breaking the operation into small components to optimise the operation of TRS using a widely used 0-D modelling methodology. The approach results in a minimum 10% increase in energy output, without the inclusion of pumping, in comparison to the maximum energy output using a similar operation for all tides. This increase in energy will be approximately 25% more when pumping is included. The optimised operation schemes are used to simulate the lagoon operation using a 2-D model and the differences between the results are highlighted.

scholarly journals Sea Wave Energy. A Review of the Current Technologies and Perspectives

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6604
Author(s):  
Domenico Curto ◽  
Vincenzo Franzitta ◽  
Andrea Guercio
Keyword(s):  
Wave Energy ◽  
Power Plants ◽  
New Technologies ◽  
Morphological Characteristics ◽  
Electrical Energy ◽  
Wave Energy Converter ◽  
Tidal Range ◽  
Ocean Current ◽  
Energy Converter ◽  
Ocean Thermal Energy

The proposal of new technologies capable of producing electrical energy from renewable sources has driven research into seas and oceans. Research finds this field very promising in the future of renewable energies, especially in areas where there are specific climatic and morphological characteristics to exploit large amounts of energy from the sea. In general, this kind of energy is referred to as six energy resources: waves, tidal range, tidal current, ocean current, ocean thermal energy conversion, and saline gradient. This review has the aim to list several wave-energy converter power plants and to analyze their years of operation. In this way, a focus is created to understand how many wave-energy converter plants work on average and whether it is indeed an established technology.

Evolution of a nourished sand beach under low wave energy in Thailand

Shore & Beach ◽  
2021 ◽  
pp. 36-54
Author(s):  
Jirat Laksanalamai ◽  
Nobuhisa Kobayashi
Keyword(s):  
Water Depth ◽  
Wave Energy ◽  
Surf Zone ◽  
Tidal Range ◽  
Gulf Of Thailand ◽  
Medium Sand ◽  
Sand Beach ◽  
Profile Changes ◽  
One Year ◽  
Upper Gulf Of Thailand

Sand beaches are essential for coastal tourism in Thailand, but erosion narrowed some beaches significantly over the years. Pattaya is a famous resort near Bangkok in the upper Gulf of Thailand. The Pattaya beach is microtidal with the average tidal range of 1.5 m. The average significant wave height is 0.2 m and the wave energy is low. The beach was widened by placing 130 m3/m of medium sand along the shoreline length of 2.8 km between two terminal groins constructed in 2018. The bathymetry and topography were measured in 2015, 2019, and 2020. Approximately 14% of the placed sand in the water depth less than 2 m was lost after one year, as may be expected for nourished beaches. The bathymetry change in the water depth of 2-4 m varied alongshore. The sand volume change in this offshore zone beyond the surf zone was as large as that in the landward sand placement zone. The assumption of negligible profile changes seaward of a closure depth is not applicable to this beach during 2015-2020.

Wave and tidal power

2007 ◽  
Author(s):  
Dean L. Millar
Keyword(s):  
Wave Energy ◽  
Tidal Current ◽  
High Efficiency ◽  
Energy Resource ◽  
Energy Difference ◽  
Tidal Range ◽  
Tidal Power ◽  
Floating Structures ◽  
Wave Energy Converters ◽  
High Tidal Range

This chapter reviews how electricity can be generated from waves and tides. The UK is an excellent example, as the British Isles have rich wave and tidal resources. The technologies for converting wave power into electricity are easily categorized by location type. 1. Shoreline schemes. Shoreline Wave Energy Converters (WECs) are installed permanently on shorelines, from where the electricity is easily transmitted and may even meet local demands. They operate most continuously in locations with a low tidal range. A disadvantage is that less power is available compared to nearshore resources because energy is lost as waves reach the shore. 2. Nearshore schemes. Nearshore WECs are normally floating structures needing seafloor anchoring or inertial reaction points. The advantages over shoreline WECs are that the energy resource is much larger because nearshore WECs can access long-wavelength waves with greater swell, and the tidal range can be much larger. However, the electricity must be transmitted to the shore, thus raising costs. 3. Offshore schemes. Offshore WECs are typically floating structures that usually rely on inertial reaction points. Tidal range effects are insignificant and there is full access to the incident wave energy resource. However, electricity transmission is even more costly. Tidal power technologies fall into two fundamental categories:1. Barrage schemes. In locations with high tidal range a dam is constructed that creates a basin to impound large volumes of water. Water flows in and out of the basin on flood and ebb tides respectively, passing though high efficiency turbines or sluices or both. The power derives from the potential energy difference in water levels either side of the dam. 2. Tidal current turbines. Tidal current turbines (also known as free flow turbines) harness the kinetic energy of water flowing in rivers, estuaries, and oceans. The physical principles are analogous to wind turbines, allowing for the very different density, viscosity, compressibility, and chemistry of water compared to air. Waves are caused by winds, which in the open ocean are often of gale force (speed >14 m/s).

Community structure and zoogeographic affinities of the coastal fishes of the Dampier region of north-western Australia.

1985 ◽  
Vol 36 (2) ◽  
pp. 247 ◽  
Author(s):  
SJM Blaber ◽  
JW Young ◽  
MC Dunning
Keyword(s):  
Community Structure ◽  
Western Australia ◽  
High Tide ◽  
Organic Content ◽  
Tidal Range ◽  
Nursery Ground ◽  
North West ◽  
Physical Conditions ◽  
The North ◽  
North Western

The species composition and broad trophic structure of the mangrove creek and open shore fish communities of the Dampier region in tropical north-western Australia are described. The habitats are characterized by a lack of freshwater influence, low turbidity and a tidal range in excess of 4 m. Both mangroves and open shores have a diversity of species typical of Indo-west Pacific coastal waters but the physical conditions have modified the community structure both to exclude many families that prefer areas of higher turbidity and reduced salinity, and to include others that usually occur only in clear waters. The fish faunas of the mangroves (113 species) and open shores (106 species) are compared: 54 species were common to both. The deeper waters were dominated by piscivores, which penetrated throughout the mangroves at high tide. Iliophagous species were abundant, particularly in the mangroves where the organic content of the substratum (7.8-8.2%) was not reduced markedly compared with other areas of the Indo-Pacific, despite the lack of freshwater inflow. The clear and deep water in the mangroves at high tide favour predation on juveniles by piscivorous fishes and reduce the effectiveness of such areas as nurseries. There is virtually no overlap of the fauna with that of the deeper waters (>20 m) of the North West Shelf, and the inshore region is not a significant nursery ground for any of the commercially important deeper water species.

MODELING SPILLED OIL PARTITIONING IN NEARSHORE AND SURF ZONE AREAS

1985 ◽  
Vol 1985 (1) ◽  
pp. 379-383 ◽  
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.

MECHANISM AND COUNTERMEASURES OF WAVE OVERTOPPING FOR LONG-PERIOD SWELL IN COMPLEX BATHYMETRY

2012 ◽  
Vol 1 (33) ◽  
pp. 45
Author(s):  
Hiroaki Kashima ◽  
Katsuya Hirayama
Keyword(s):  
Deep Water ◽  
Wave Energy ◽  
Spatial Relationship ◽  
Wave Transformation ◽  
Wave Overtopping ◽  
Long Period ◽  
Wave Characteristics ◽  
Water Region ◽  
Wave Heights ◽  
Shallow Water Region

Recently, coastal disasters due to long-period swells induced by heavy storms and catastrophic typhoons have increased at Japanese coasts and harbors. Long-period swells are more susceptible to the bottom bathymetry of the offshore deep water region and their wave heights locally increase due to the concentration of wave energy caused by the complex bottom bathymetry in the relatively shallow water region. In addition, the wave overtopping rate may increase due to the long waves in front of the seawall induced by the long-period swells. However, the spatial relationship between wave characteristics and wave overtopping discharges in the complex bathymetry are not well known owing to a lack of detailed measurements. In this study, model experiments were conducted by using a large basin to investigate the spatial characteristics of wave transformation and wave overtopping focusing on the heavy wave overtopping damages caused by the arrivals of long-period swells at the Shimoniikawa Coast in 2008. Effective countermeasures against wave overtopping are also discussed based on their characteristics.

scholarly journals Tidal Type Determination on Manokwari Shipping Chanel by Using Admiralty Method

2018 ◽  
pp. 57
Author(s):  
Suhaemi Suhaemi ◽  
Syafrudin Raharjo ◽  
Marhan Marhan
Keyword(s):  
Water Level ◽  
Full Moon ◽  
High Tide ◽  
High Water ◽  
Tidal Range ◽  
Tidal Amplitude ◽  
Gravitational Forces ◽  
Sea Transportation ◽  
Gravitational Pull ◽  
Tidal Waters

Tidal waters are very important for port interests, sea transportation, fisheries industry, coastal engineering and coastal area mitigation. Tidal height formed is a superposition of tidal amplitude due to the gravitational pull of the sun, moon and earth. The Tidal components are K1, O1, P1, S2, M2, K2, M4, MS4. This study aims to determine the components and types of tides in the shipping channel of Manokwari-West Papua using the admiralty method. Formzahl 0.732 number means the type of tidal that is formed is mixed tide prevailing semidiurnal, two high and low tide, two high and one low tide or two times low tide one high tide in a day. Mean Sea Level (MSL) was caused by water conditions, coastlines and bathymetry, the gravitational forces of the moon and sun. The MSL was obtained 98 cm. large tidal range occurs during full moon conditions and low tides occur during perbani (1.62-2.44 m). The amplitude Mean High Water Level level reaches 279 cm and Mean Low Water Level reaches -83 cm.

scholarly journals Round Robin Testing: Exploring Experimental Uncertainties through a Multifacility Comparison of a Hinged Raft Wave Energy Converter

2021 ◽  
Vol 9 (9) ◽  
pp. 946
Author(s):  
Thomas Davey ◽  
Javier Sarmiento ◽  
Jérémy Ohana ◽  
Florent Thiebaut ◽  
Sylvain Haquin ◽  
...  
Keyword(s):  
Wave Energy ◽  
Physical Modelling ◽  
Round Robin ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Mean Power ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Similar Good ◽  
Six Degree Of Freedom

The EU H2020 MaRINET2 project has a goal to improve the quality, robustness and accuracy of physical modelling and associated testing practices for the offshore renewable energy sector. To support this aim, a round robin scale physical modelling test programme was conducted to deploy a common wave energy converter at four wave basins operated by MaRINET2 partners. Test campaigns were conducted at each facility to a common specification and test matrix, providing the unique opportunity for intercomparison between facilities and working practices. A nonproprietary hinged raft, with a nominal scale of 1:25, was tested under a set of 12 irregular sea states. This allowed for an assessment of power output, hinge angles, mooring loads, and six-degree-of-freedom motions. The key outcome to be concluded from the results is that the facilities performed consistently, with the majority of variation linked to differences in sea state calibration. A variation of 5–10 % in mean power was typical and was consistent with the variability observed in the measured significant wave heights. The tank depth (which varied from 2–5 m) showed remarkably little influence on the results, although it is noted that these tests used an aerial mooring system with the geometry unaffected by the tank depth. Similar good agreement was seen in the heave, surge, pitch and hinge angle responses. In order to maintain and improve the consistency across laboratories, we make recommendations on characterising and calibrating the tank environment and stress the importance of the device–facility physical interface (the aerial mooring in this case).

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