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1
Quinn, Paul Anthony. "Breaking waves on beaches". Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/12822.
Testo completoAbstract (sommario):
A comprehensive experimental study has been carried out to measure the velocity field of waves breaking on two types of beach. The measurement technique of Particle Image Velocimetry (PIV) has been used throughout to measure the full-field, instantaneous velocity distributions. This technique is described in some detail with particular attention paid to the errors inherent when using PIV in this application. The first type of beach studied has a mild slope, typical of sandy beaches. PIV measurements have been carried out on 1:30 and 1:100 plane sloping beaches with monochromatic waves. The measured internal kinematics are compared to those predicted by the Boussinesq and Serre wave models, with some good agreement. However, there are some significant differences in the near-surface region of the wave crest which tend to increase as the waves propagate up the beach. In addition to these theoretical comparisons, the Integral Properties of the waves on the 1:30 slope are calculated from the PIV measurements. The second type of beach examined is typical of a shingle beach. In addition to being steeper than the previous case, these beaches are also profiled, representing the shape of the beach formed under storm conditions. Two profiles have been modelled and three different monochromatic waves have been measured on each. The wave breaking processes are described and velocity measurements from each wave on both beaches are shown. Furthermore, a near-bed velocity comparison between the three waves at various positions along each beach has also been carried out in order to explain any potential on-shore and off-shore sediment motion.
2
Acuna, Adrian Pedrozo. "Concerning swash on steep beaches". Thesis, University of Plymouth, 2005. http://hdl.handle.net/10026.1/1672.
Testo completoAbstract (sommario):
This investigation focuses on the prediction of sediment transport and beach evolution in coarse-grained beaches. This includes observed morphological changes on both gravel and mixed beaches from experimental investigations at the Large Wave Flume (GWK) in Hanover. Germany. The recorded measurements show that the majority of morphology change took place adjacent to the zone of wave-breaking, close to the shoreline in both cases. Based on these observations, the discussions are carried out with psirticular regard to the observed tendency for onshore transport axid profile steepening in the swash zone. The aim is to identify the cross-shore hydrodynamics and sediment transport mechanisms involved, to advance understanding of this type of beach and to improve our qucintitative capabilities for predicting shoreline and morphological changes in this zone. With this in mind, this thesis includes a discussion of the physical processes related to swash hydrodynamics and sediment transport. It also introduces the description of the mathematical framework used to study wave hydrodynamics in the swash zone. Emphasis is given to the Boussinesq equations which have been found to be a suitable approach. For these equations an evaluation of the two available shoreline boundary conditions is carried out and it is shown that the moving shoreline accurately reproduces the velocity field in the swash zone. The profile evolution investigation is carried out evaluating the transport rates from a bed-load sediment transport formulation coupled with velocities calculated from a set of Boussinesq equations (Lynett et al 2002). Then the equation for conservation of sediment is solved to estimate the morphological changes as proposed by (Rakha et al 1997). It is shown that such an approach is useful to investigate the processes that control this evolution. A discussion on the influence of bottom friction on the predicted profiles is presented. Numerical results in both beaches show that the use of a higher friction factor f during uprush improves the simulations of morphological changes. However, the variation of friction by itself was not able to reproduce the measured profiles. A plausible reason to explain this is that further mechanisms other than friction play an important role in the overall response of coarsegrained beaches. For both beaches it is established that, if the efficiency factor (C) in the sediment transport equation and bottom friction are kept the same in the uprush and backwash, accurate representation of profile evolution is not possible. Indeed, the features of the predicted profiles are reversed. When the C parsimeter is set larger during the uprush than during the backwash, the predicted profiles are closer to the observations. Differences between the predicted profiles from setting non-identical C-values and friction factors for the swash phase, are believed to be linked to both the infiltration effects on the flow above the beachface, the bore collapse picking up sediment from the bed, and the accelerated flow in the uprush. The discussion is made with reference to main physical processes acting over the beachface for both the mixed and gravel beach.
3
Trim, Louise. "Physical modelling of shingle beaches". Thesis, University of Brighton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399044.
Testo completo
4
Heinze, Heather W. "Anthropogenic Influences and Meteorological Effects: How They are Changing the Sand Beaches in Southern Maine". Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/HeinzeHW2001.pdf.
Testo completo
5
Coutts-Smith, Aaron J. "The significance of mega-rips along an embayed coast". Phd thesis, School of Geosciences, 2004. http://hdl.handle.net/2123/6082.
Testo completo
6
Finlayson, David P. "The geomorphology of Puget Sound beaches /". Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/11035.
Testo completo
7
Brown, Jenna A. "Cross-shore exchange on natural beaches". Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/43882.
Testo completoAbstract (sommario):
Approved for public release; distribution is unlimitedThe cross-shore exchange of material is examined on beaches of varying morphology and hydrodynamics. On a dissipative, rip-channeled beach in Monterey, California, field measurements of the rip current vertical structure reveal depth-uniform flows inside the surf zone, and surface-dominated flows with rotation over depth outside the surf zone. Aperiodic, very low frequency pulsations in the near-surface velocity were found to control the mean rip current flow. Observations of Lagrangian surface drifters released on the inner shelf resulted in a new theory of material transport on a rip-channeled beach, where rip current pulses episodically expel material offshore through rip channels, and momentum-driven surfzone circulations pull the material back onshore over shoals to satisfy a mass balance, with no material being completely removed from the nearshore system. Advection and diffusion processes on a steep, reflective beach at Carmel River State Beach, California, are also investigated using measurements of the temporal and spatial evolution of dye released in the surf zone. A net offshore transport did exist, and the mixing and transport processes inside and outside the surf zone were independent. Overall, this work provides new insights into the fate of material transported between the surf zone and inner shelf on natural beaches.
8
Brown, Susan Jayne 1967. "Longshore currents on seawall-protected beaches". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/39079.
Testo completo
9
Stefanova, Stela K. "Measuring the recreational value of changes in beach access, beach width, and vehicle access in the Mid-Atlantic region application of random utility models /". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 192 p, 2009. http://proquest.umi.com/pqdweb?did=1892027481&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Testo completo
10
Gardner, Nathan. "Formation and Age of Raised Marine Beaches, Northern Scott Coast, Antarctica". Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/GardnerN2002.pdf.
Testo completo
11
Dreyer, Nicolaas Burger. "Within- and between-beach variation in intertidal macrofaunal communities inhabiting two Transkei sandy beaches". Thesis, Nelson Mandela Metropolitan University, 2008. http://hdl.handle.net/10948/1070.
Testo completoAbstract (sommario):
Until recently most sandy beach studies have made use of snapshot samples but the validity of this approach has been widely questioned. In this study we attempt to resolve this issue by repeatedly sampling two beaches using a stratified random design. Three sampling sessions took place, each approximately six months apart. The three sites on the first beach were selected according to the type of beach (reflective, intermediate and dissipative) with each morphological type duplicated on the second beach. Many of the physical variables measured had significant differences between the sampling sessions but only a few were significantly different between the Sites. Very few of the individual physical variables had significant relationships with the sandy beach macrofaunal abundance and density. However, composite indices had a greater number of significant relationships with the macrofaunal abundance and density. Also very few significant relationships were seen between the species richness and the physical variables of the beaches studied. Effluent line crossing frequency was the only physical variable that could predict species richness but it was considered a weak predictor. Changes in the zonation patterns within and between beaches were also investigated. The highest concentration of taxa and individuals was found near the low-water mark with a gradual reduction of both towards the high-water mark. Some of the sandy beach community variables (abundance, density and species richness) showed significant difference between the sampling sessions but no significant differences were seen between the two beaches. The presence of three zones was noted using MDS plots and Cluster diagrams. However, using a SIMPER analyses, four zones with the possibility of a fifth was noted.
12
Check, Lindsay A. (Lindsay Anne). "Analysis of Longshore Sediment Transport on Beaches". Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4886.
Testo completoAbstract (sommario):
The present study investigates longshore sediment transport for a variety of bathymetric and wave conditions using the National Oceanic Partnership Program (NOPP) NearCoM Model. The model is used to determine the effects of wave shape and bathymetry changes on the resulting longshore sediment transport. The wave drivers, REF/DIF 1 and REF/DIF S, are used to assess the effects of monochromatic and spectral waves on longshore sediment transport, respectively. SHORECIRC is used as the circulation module and four different sediment transport models are used. Longshore transport comparisons are made with and without skewed orbital velocities in the shear stress and current velocities. It is found that the addition of skewed orbital velocities in shear stress and transport formulations increases longshore sediment transport by increasing time-varying effective shear stress. The addition of skewed orbital velocities greatly increases the transport due to advection by waves.
The localized longshore sediment transport is calculated using a generic physics based method and formulas by Bagnold, Bailard, and Bowen, Watanabe, and Ribberink. The transport results for each scenario are compared to the total transport CERC, Kamphuis, and GENESIS formulas. The bathymetries tested include an equilibrium beach profile, cusped beach profiles, and barred beach profiles with different bar locations. The longshore transport on an equilibrium beach profile is modeled for a 0.2 mm and 0.4 mm grain size and transport is compared to the CERC formula. The longshore sediment transport for d=0.2 mm is larger than d=0.4 mm when wave power is small, but as wave power increases the transport for the larger grain size dominates. The transport is also affected by the addition of cusps and bars on an equilibrium beach profile. The barred beach is modified to compare transport between waves breaking at the bar, before the bar, and after the bar. The features affect the transport when the wave powers are small, but as wave heights increase the cusp and bar features induce little change on the longshore sediment transport.
13
Poate, Timothy George. "Morphological response of high-energy macrotidal beaches". Thesis, University of Plymouth, 2012. http://hdl.handle.net/10026.1/1094.
Testo completoAbstract (sommario):
Spatial data collected over 3 years is presented to assess the extent of morphological variability under seasonal and storm waves at four high-energy macrotidal beaches. A novel approach is adopted to identify and classify the beach response which is used to assess the relative stability of the system to changes in the dominant forcing conditions. Field measurements and modelling simulations using XBeach provide further support for a storm dominated system exhibiting relative stability. Morphologically the beaches range from dissipative to intermediate and are characterised by low tide bar/rip morphology which plays a key role in the nearshore dynamics and beach safety. Located in the north coast of Cornwall the sites are exposed to high-energy waves that dominate the stability and behaviour of beaches in this region. The growing need for marine renewable energy in the UK has led to the deployment of a Wave Hub on the seabed off the north coast of Cornwall, designed to provide grid connection for wave energy devices (WECs). As a unique development much has been done to address concerns over potential impacts cause by arrays of WECs during its construction and operational lifetime; these predicted impacts include changes in the quality of waves for surfing and effects on the beach dynamics which determines beach safety through the presence of bar/rip features. In this thesis three years of monthly topographic surveys were collected from beaches in the proposed Wave Hub shadow zone to assess their morphodynamic variability. Realtime kinematic (RTK) GPS surveys were undertaken using an all-terrain vehicle to measure the three dimensional (3D) morphology at four beaches (Perranporth, Chapel Porth, Porthtowan and Gwithian) situated along a 23 km stretch of the north Cornish coast. In addition nearshore wave data, in-situ hydrodynamic measurements, local tide gauges and Argus video data allowed detailed analysis of process-response mechanisms for long term (yearly); seasonal (monthly); storm (weekly/daily); and tidal (hourly) morphological behaviour. Of particular interest was the degree to which the beaches displayed bar/rip morphology, characterised by the three dimensionality (3D) of beach response, which determines wave breaking and affects beach safety. Using a combination of measured shoreline variability and empirical beach classification schemes, the response to changes in the wave conditions at each beach have been assessed. The sites exhibited net long term accretion derived from the intertidal beach volume. Throughout the survey period intersite similarity in beach response was observed in response to storm waves, yet coupling between the seasonal wave climate and the beach morphology was not evident at any of the sites, due to the dominance of recovery phases following storm events. The role of increased wave conditions (exceeding Hs=4 m) during sustained storm events (> 50 hrs) led to offshore transport from the beach face to the subtidal bar region. Post-storm recovery was characterised by onshore transport and the development of substantial 3D low tide morphology. Under normal wave conditions (Hs=1.6 m) the dominant 3D features smoothed out as channels in-filled and bars reduced over a period of 2-3 months. This cyclicity was observed on ~3 occasions at the northern sites, while Gwithian remained more stable throughout; reflecting the more sheltered position of the beach. Overall the beaches exhibited a significant storm dominated morphological response cycle, unlike the more familiar winter/summer seasonal response. Nearshore bar behaviour at Perranporth and Porthtowan, assessed using ARGUS images, was dominated by offshore migration (ca.20 m/yr) following closely the net intertidal accretion, while bar shape exhibited changes over monthly periods. Intensive field studies of morphological change, nearshore current flows and surf zone wave conditions were undertaken at Porthtowan during small swell dominated waves and large energetic storm conditions in May and October 2010 respectively. The field data highlighted accretionary response under small swell dominated waves, and strong offshore directed undertow flows (0.5 m/s-1) during erosive energetic conditions (>Hs = 4m) which were then related to the monthly surveys. These results were applied to XBeach model simulations which helped further identify the importance of antecedent morphology and the complexities of intertidal geology in controlling beach response. The study provides the longest continuous record of beach morphology dynamics for macrotidal energetic sites and provides a valuable addition to work in this field. The dominance of storm driven morphological response was clear with highly threedimensional morphology developing under post storm conditions and continued beach evolution driven by the seasonal conditions. Antecedent morphology was found to be a key element of beach response with geological control an additional component. The projected reduction in wave conditions due to the Wave Hub and the natural variability observed indicates the sites are unlikely to shift significantly from their current dynamic state in response to the Wave Hub, and as such the potential impact on nearshore and beach dynamics is minimal.
14
Evans, Darren. "Swash on steep and gently-sloping beaches". Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/12664.
Testo completoAbstract (sommario):
In the last twenty years, the importance of sediment transport in the swash zone has been established. The disproportionately high sediment transport rates in this region make its inclusion in general nearshore models vital. As part of this U.K. Natural Environmental Research Council project (grant number: NERlA/S/1999/00144), high frequency (8 Hz) measurements were made of the water depth and vertical variations in suspended sediment concentration and water velocity, using state-of-the-art instrumentation. Further measurements included nearshore and offshore wave conditions, tidal elevations, wave run-up limits, groundwater variations, sediment grain size distributions, beach slopes and changes in morphology at time-scales from minutes to weeks. Fieldwork was carried out on a gently-sloping (tan p - 0.03; d50 ~ 0.27 mm) and steep beach (tan p - 0.09; d50 ~ 0.55 mm). Both experience similar wave climates which allows a direct comparison between hydrodynamics and sediment transport in the swash zone.
15
Smith, Albert William S. "The function and behaviour of natural beaches". Thesis, Queensland University of Technology, 1986. https://eprints.qut.edu.au/36454/1/36454_Smith_1986_Vol-1.pdf.
Testo completoAbstract (sommario):
This study may well be considered to represent a rather simplistic
contribution, towards the science of coastal engineering. This is in
fact, perhaps as it should be, because the mathematics involved, are
of the most basic kind, and no profound theories have been expounded.
This work has nothing to do with the development of existing theories
or existing dogma, within the current realms of the particular discipline.
That must remain for others.
This writer is not a scientist within any stretch of the classification,
he remains a simple engineer, who has spent most of his life, in the
role of being that of a basic observer. This status is often regarded
as being that of a semi-professional technician, and perhaps that is
rightly so. On the other hand, the common observer, in recording his
observations, might still well contribute something of value. He might
for example, document his prototype experiences particularly where he
finds that classical theory does not fit the "facts" as he sees them.
He might also well ponder why these theories appear to predict natural
process phenomenon, that cannot be seen on the prototype, or where the
real prototype can be readily seen to be doing something different.
These things are what this study is made from.
In dealing with coastal process observations, the writer's first introduction
to the subject occurred late in 1938, on the Paekakariki coast
of New Zealand. At that time, very profound changes were affecting the
entire fabric of this coastal area, after many decades of relatively
prior stability. At that time, a coastal recession of 50m in one year
was obvious, as was the degradation of a previous completely sandy beach,
into a residual boulder remnant within three years. These things exerted
an immense impact on this writer as a juvenile - he could appreciate
the dramatic effect of Nature even then - guided no doubt by his engineer
father, a Marine Engineer of vast experience.
At least the writer's family, always expounded the thesis, that an ounce
of observation was often worth a pound of theory, and perhaps sometimes,
even a ton. In very many ways, it may well be reasonable to conclude
that this very primitive concept, may still hold some reasonable value.
This work therefore, is an attempt to record the results of a lifetime's observations of natural coastal processes, together with a rather
hesitant approach towards postulating the mechanisms, that are the
central essence of these processes.
If much of this work is orientated towards interpretating, the subtle
interactions of Nature, in addressing coastal engineering actions and
responses, then this has been deliberate. This in many ways, is only
a crude representation of how Nature really works. Nature, it might
be noted, appears quite benign for most of the time, such that when
an extreme event hits us, we often consider this an extraordinary event,
in fact often as an "Act of God". This is not Nature's way at all.
In everything that Nature does, she displays a very single minded,
pragmatic, quite re~entless and ruthless approach to every natural
reaction. Every natural resource is treated for the maximum of economy
of resources - nothing is ever wasted. If any action cannot be counterbalanced
by the available reaction resources, then these current resources
are instantly discarded (to be used later for other purposes) and another
line of defence mechanisms are immediately called into action. The more
one may consider these natural processes, then the more obvious the
fantastic inter-relationship~ that are called into action - may become
obvious.
Mankind, in its engineering arro5c:illce, often chooses to ignore Nature's
action, and response mechanisms. Coastal engineers are particularly
prone to fall into this error. They only so often conclude that their
small scale hydraulic flumes, may completely eliminate the total fury
of Nature, on the prototype, as a hazard. In this, they have to date,
proven to be sadly in error. The dramatic failures at Keelung, Sines,
Bilbao, San Ciprian (and others) all attest to this miss-placed, self
appointed, over-confidence in engineering interpretations, of Nature's
real and often unexpectedly "raw" behaviour. It seems that the design
of major coastal structures, is commonly accepted as being capable of
conclusion within offices and laboratories, far remote from the site.
It is tendered here, that this isolationist approach, must be an open
invitation to the unexpected, and thus to total failure. Such, only
happens so often, in real coastal engineering practice.
This work therefore, is entirely related towards an attempt to interpret
and explain Nature's processes, and all based upon observations on the prototype. For certain, many of the interpretations made, may later
be shown to be in error. However, one must start somewhere, and this
is at least an attem:pt to do so. Many of the things said herein,
may appear to the more orthodox, to be irrational, unprecedented or
even nonsense. As such, the conventional orthodox are welcome to their
own opinions. What is set-out herein, is entirely the writer's opinions,
and he will stand by them. These opinions however, are not the resultants
of reading only other people's publications nor interpreting only
other people's data. What is recorded here is the results of sim:ple
site observation on dozens of prototypes, over a period of forty years
or more. Whether these observations are of any value, must in the end,
be up to the reader. Only time will tell.
16
Taylor, Amy Margaret. "Spatiotemporal morphodynamics of a recently modified beach system, Aberdeen, UK". Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=225799.
Testo completoAbstract (sommario):
The prediction of morphological responses of natural and engineered beaches to the prevailing wave, tide and wind conditions continues to be a challenge due to the wide variability in site conditions and the underlying complexities of the processes involved. For this reason, field measurements, especially with a good spatial and temporal resolution, play a critical role in monitoring the performance of intervention work. This thesis presents the results of a five-year study at Aberdeen beach on the North Sea coast of the UK, with the aim of obtaining and analysing high-quality field measurements of beach dynamics before and following beach nourishment and the installation of nearshore breakwaters. Beach topographic data were collected between June 2006 and July 2011 at approximately monthly intervals using real time kinematic GPS, augmented by Argus video monitoring. An assessment of the horizontal and vertical errors of the Argus system found it to be comparable to other similar installations. The initial response of the area of beach subject to recent intervention works was the formation of stable bays in the lee of the nearshore structures, making this zone morphologically distinct from other areas of the beach. Time-synchronous wave data was collected from nearshore wave buoy measurements, or derived from transformed Met Office model-predicted wave data, and were considered in relation to the timing of beach morphology responses to the prevailing wave conditions. A strong link was observed between the 30-day average wave height and the beach dynamic, with erosion commencing when Hm0 rose above 1 m, and antecedence being an important factor in beach response to successive winter storm events. The data and insights from the present study can be used to develop better predictive models and coastal monitoring strategies. Future studies seeking to further understand beach response would benefit from the ability to capture variation within tidal cycles, and to be able to connect the beach to wider nearshore and offshore bedforms and marine processes.
17
Miller, Gregory Chad. "Observations of the formation and maintenance of beach cusps on Del Monte Beach in Monterey, California". Thesis, Springfield, Va. : Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA403566.
Testo completo
18
Figlus, Jens. "Seasonal and yearly profile changes of Delaware beaches". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 198 p, 2007. http://proquest.umi.com/pqdlink?did=1253510781&Fmt=7&clientId=79356&RQT=309&VName=PQD.
Testo completo
19
Miles, Jonathon Rupert. "Enhanced sediment transport near seawalls and reflective beaches". Thesis, University of Plymouth, 1997. http://hdl.handle.net/10026.1/1901.
Testo completoAbstract (sommario):
This thesis describes results of a field experiment to examine the effect of wave reflection on suspended sediment transport in front of a seawall. Two instrument rigs were set up on the beach at Teignmouth, South Devon, U.K., in June 1995. One rig (the seawall rig) was attached to a protruding section of seawall, positioning the instruments 1.2m seaward of the wall. The other rig (the beach rig) acted as a control and was positioned 135m downcoast where the seawall is set back so that conditions were those of a natural beach. At each rig high frequency measurements of wave elevation, current velocity and suspended sediment concentrations were made using pressure transducers (PTs), bi-axial electromagnetic current meters (EMCMs) and optical backscatter sensors (OBSs) respectively. Wave heights during the experiment were typically in the range 0.1 <Ho<0.3m in deep water outside the surf zone and incident wave periods were around 4 seconds. Measurements were made in a range of water depths from 0.5m to 2.5m. At the natural beach, the reflection coefficient (R = reflected wave amplitude / incident wave amplitude) was found to be dependent on frequency, with low frequency waves (f<0.08Hz) being preferentially reflected (0.7<R<0.9), while incident waves (O.I<f<0.45Hz) were dissipated (O.1<R<0.2). In front of the seawall the incident wave reflection coefficient was high (0.75<R<0.9), indicating only a small amount of dissipation and thus an effective doubling of energy over the sea bed. This was found to increase the suspended sediment concentrations in the water column. For similar water depths (-0.5m), and instrument heights (~ -0.2m) instantaneous maximum sediment concentrations in front of the wall reached 9kg/m3, compared with only 1.2kg/m3 on the adjacent natural beach, despite similar incident wave conditions. Mean suspended sediment concentrations in front of the wall were also enhanced, ranging from 0.08kg/m3 to 2.8kg/m3, while at the beach rig values were typically in the range 0.08kg/m to 0.8kg/m3. At the seawall, mean and maximum suspended sediment concentrations were found to be dependent on water depth. Suspended sediment concentrations increased with decreasing depth. Guza et al.'s (1984) time domain method for separating incoming and outgoing waves was adapted to allow the incoming and outgoing wave contributions to the cross-shore sediment transport to be analysed. Incoming waves transported sediment onshore in both beach and wall cases, with typical values of the oscillatory transport associated with the incoming waves being 0.0005 < Ujn'Cs'bcach < 0.011 kg/m2/s and 0.0011 < Uin'Cs'u^i < 0.0187kg/m2/s. At the beach this resulted in a net onshore sediment transport by the waves, while in front of the wall offshore sediment transport associated with the reflected (outgoing) waves balanced the onshore sediment transport. Although the net cross-shore transport in front of the wall in this case was therefore reduced by wave reflection, the gross cross-shore transport was increased by a factor of two. Sediment accretion which was observed at the top of the natural beach was not observed in front of the wall, implying that the presence of the wall inhibited beach recovery in these accretionary conditions. Mean cross-shore sediment transport rates were also larger at the wall than at the beach. Typical values were u Cs wall = 0.05kg/m2/s compared with u Cs beach = 0.002kg/m2/s. This was attributed to the larger values of mean sediment concentration at the wall. Mean cross-shore sediment fluxes at the wall were directed onshore at the depth of the instruments, although this did not lead to accretion. It is suggested that sediment was prevented from settling by increased wave stirring, and was transported downcoast by enhanced longshore currents in front of the wall. Both longshore currents and longshore sediment transport rates were found to be increased in front of the wall. Typical values of the mean longshore sediment flux were 0.0167 < v Cs UTIU < 0.320kg/m2/s, while at the beach typical values were 0.0001 < v c^ beach < 0.0142kg/m2/s in 1 m water depth. The enhanced longshore transport in front of the wall resulted in a bar forming downcoast from the end of the wall. The seawall reflects incident waves back over the beach and this results in an increase in sediment suspension. The following were all found to be enhanced by the presence of the seawall: wave reflection, mean and instantaneous maximum suspended sediment concentrations, onshore transport by the incident waves, offshore transport by reflected waves, gross oscillatory cross-shore sediment transport, mean cross-shore sediment transport and mean longshore sediment transport rates.
20
Gemmell, Sally L. G. "Sediment transfer from gravel bed rivers to beaches". Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274782.
Testo completo
21
Mitchell, S. S. "The valuation of beaches as urban open space". Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/4784.
Testo completoAbstract (sommario):
Bibliography: leaves 23-24.The beach is a unique open space in the urban context. It is a dynamic aggressive environment that has in the past been ignored as an open space that has special qualities. While it has been seen purely as a recreational facility, ecosystem services and intrinsic values have been ignored. In Cape Town planning guidelines now set store on the value of open space, however the fear is that there may be insufficient emphasis on the beach as an urban edge and an open space element. While ecosystem service can and have been calculated intrinsic values present some difficulties.
22
Yates, Marissa L. "Seasonal sand level changes on southern california beaches". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3342173.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed February 13, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 124-133).
23
Lam, Chi-chung. "Monitoring of beach water quality in Hong Kong /". Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21301761.
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24
楊凱恩 e Hoi-yan Esther Yeung. "Beach erosion and recovery on the beaches of southeast Hong Kong Island, Hong Kong SAR, China". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42904559.
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25
Yeung, Hoi-yan Esther. "Beach erosion and recovery on the beaches of southeast Hong Kong Island, Hong Kong SAR, China". Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42904559.
Testo completo
26
Chenault, Carla D. "Understanding long-term beach width change in the Oceanside littoral cell, California". Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.
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27
Hawkins, Magdalena Johanna, e Lorenz Hauser. "An evaluation of the morphological and genetic diversity of Eurydice occurring on South African sandy beaches". Thesis, Nelson Mandela Metropolitan University, 2016. http://hdl.handle.net/10948/6708.
Testo completoAbstract (sommario):
This study evaluated the diversity of the genus Eurydice on sandy beaches in South Africa by analysis of morphological as well as genetic data. Type specimens of the three Eurydice species currently known from South Africa, E. longicornis, E. kensleyi and E. barnardi were obtained from the Museum für Naturkunde in Berlin and the Iziko Museum in Cape Town, South Africa. These specimens were studied in order to become familiar with their morphology. Eurydice individuals obtained from 30 sites spanning the South African coast, from Port Nolloth on the north-west coast to Bhanga Nek on the north-east coast were then examined. The two species E. kensleyi and E. barnardi, as well as four new morphospecies (A, B, C and D) were discriminated from these individuals by suites of morphological character types. Morphospecies A, B, C and D were therefore delimited according to the Phenetic Species Concept. None of the Eurydice individuals examined exhibited the same suite of characters as E. longicornis. Molecular sequences of two mitochondrial markers, cytochrome c oxidase 1 and 16S rRNA were analysed using both distance- and monophyly based methods. Uncorrected p-distances, a Minimum Spanning Haplotype Network and Maximum Likelihood phylogenetic trees were investigated to determine genetic diversity and phylogenetic relationships in the six Eurydice morphospecies. Results from the genetic analysis made it possible to delimit morphospecies A B, C and D as phylospecies A, B, C and D according to the Phylogenetic Species Concept, thereby validating the species status of four new Eurydice species, provisionally called Eurydice A, Eurydice B, Eurydice C and Eurydice D. This increases the total number of Eurydice species from South Africa to seven, of which six form part of the macrofauna of sandy beaches. The outcomes of this study represent an important step in the resolution of the taxonomy of the genus Eurydice in South Africa and enhance current knowledge of the biodiversity of sandy beach macrofauna, thus facilitating better-informed decisions on conservation policies and management to the benefit of conservation of biodiversity on sandy beaches in South Africa.
28
Pierce, Lydia R. "Lake waves and gravel beach variation, Loch Lomond Scotland". Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325392.
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29
Zoulas, James Gary. "Beach changes in the San Pedro Littoral Cell, Southern California, 1930-2007". Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1666392701&sid=28&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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30
McKay, Matthew G. "An analysis of public access to municipal beaches on the Long Island Sound in Connecticut /". View abstract, 2001. http://library.ccsu.edu/ccsu%5Ftheses/showit.php3?id=1657.
Testo completoAbstract (sommario):
Thesis (M.S.)--Central Connecticut State University, 2001.Thesis advisor: David Truly. " ... in partial fulfillment of the requirements for the degree of Master of Science in Geography." Includes bibliographical references (leaves 144-149). Also available via the World Wide Web.
31
Wal, Abhilasha. "Sedimentological effects of aeolian processes active in the Tentsmuir area, Fife, Scotland". Thesis, University of St Andrews, 1993. http://hdl.handle.net/10023/15197.
Testo completoAbstract (sommario):
Present day coastal accretion at Tentsmuir is manifest in the form of hummocky dune accumulations along the shoreline. The mode and variability of the distribution of surface sediments by the wind and the magnitude of accumulation of wind laid deposits in the Tentsmuir beach-dune complex is a measure of Aeolian activity in the area. In the Tentsmuir area fine to medium grained well sorted beach sands are entrained by high to moderate energy, seasonal, directionally unimodal to bimodal winds of low variability. During the winter season the dominant winds are from the south west (blowing towards the sea) whereas, generally during the spring the more effective winds are derived from the east (blowing towards land). The bimodal winds are composed of contrasting unimodally directional winds blowing for shorter durations. Daily sea breezes are observed during the summer. Field measurements of sand transport rates, with the aid of sand traps during anemometer determined wind speeds ranging from 4 m s-1 to 20 m s-1, in the study area show that while the onshore transport vector results in rapid foredune development, the longshore and offshore component contributes to a positive beach sediment budget. However, the net beach sediment budget is a complex interplay of Aeolian, wave and tidal processes. Shear velocities on the Tentsmuir beaches ranged from 18.5 cm s-1 to 52 cm s-1 and the focal point, u' and z' values were 1.75 m s-1 and 0.03 cm respectively. In general, the variability of the short-term Aeolian sand transport rates in the Tentsmuir beach-dune subenvironments is controlled by (i) variation in wind velocity, (ii) presence or absence of vegetation, (iii) ground surface moisture, and (iv) the sand size and source limitation. The potential sand input by the onshore winds during the last eleven years is estimated to have been approximately 28,532 m3. During the same period the potential amount of sand blown towards the sea was 109,570 m3. The amount of predicted onshore sediment input (28,532 m3) compares well with the 33,000 m3 of sand estimated to have accumulated in the lee of the beach at Tentsmuir Point The close agreement of the measured and predicted values of Aeolian transport suggests that the White (1979) expression, used in the present study to predict transport rates on the beach, provides fairly reliable estimates. Very high velocity offshore winds (>9 ms-1 produce a shelly deflation surface along the backshore, surface parallel sand sheets and sand strips on the foreshore; adhesion plane bed and adhesion structures along the moist/wet tidal margin and pyramidal dunes (offshore transport across a dune ridge >2.5m high.). Onshore high velocity winds result in the formation of surface parallel sand strips on the foreshore and a high volume of Aeolian sediment accumulation in the backshore and foredune area. Prolonged days of high velocity unidirectional winds result in the formation of barchans. Medium to high wind velocities (~6-9 ms-1) produce ballistically rippled foreshore sand lobes, lee dunes downwind of tidal debris, adhesion structures (offshore/longshore transport) and some sand accumulation in the foredune area (onshore transport). Abundant parallel laminated sand, pinchout laminae, sand lenses, precipitation deposits, trough crossbeds, plant remains at places overlying beach shell layers constitute a prograding coastal dune facies at Tentsmuir.
32
Burton, Mark C. "Directional spreading effects on nonlinear waves shoaling on beaches". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA298657.
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33
Yani, Vuyolwethu Veronica. "Ecosystem health of the Nelson Mandela Bay sandy beaches". Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1075.
Testo completoAbstract (sommario):
An investigation of ecosystem functioning of sandy beaches in the Nelson Mandela Bay Municipality (NMBM) was carried out with the aim of describing their type and pollution status. Water salinity, temperature, pH, beach slope, water inorganic nutrient concentrations, urea, and chlorophyll-a concentration as well as the composition of zooplankton, phytoplankton, meiofauna, benthic microalgae and bacteria were examined at thirteen beaches. The beaches were classified into three types: short beaches; long beaches with surf diatoms; and long beaches that import biomass (without surf diatoms). Of the thirteen beaches, five were non-polluted and eight polluted with polluting human activities in and around them. Most beaches were dominated by fine sand except for St. Georges Strand where the particles were medium to fine sand and Maitland’s River Beach, Bluewater Bay and Sardinia Bay that had coarse sand. Nutrient concentrations ranged from 1.98 ± 0.10 μM to 19.30 ± 3.02 μM nitrate; 4.88 ± 1.00 μM to 11.97 ± 1.00 μM ammonium; 0.67 ± 0.00 μM to 2.31 ±1.00 μM soluble reactive phosphorus; and 0.00 to 0.03 ± 0.00 μg l-1 urea-N. Chlorophyll-a concentrations ranged from 0.04 ± 0.02 to 1.57 ± 0.11 μg l-1. Chlorophyll-a concentrations were negatively correlated to ammonium for all beach types (short beaches: r = 0.94; long importing beaches: r = 0.95 and surf diatom beaches: 0.94) and to nitrate for short and long importing beaches (short: r = 0.97 and long importing: r = 0.85). By contrast, a positive correlation was found between observed between chlorophyll-a concentrations and urea for surf diatom beaches (r = 0.93) and for long importing beaches (r = 0.73). Chlorophyll-a concentrations were negatively correlated to short beaches (r = 0.99) and long importing beaches (r = 0.76). The E. coli and total coliforms in all the sampled beaches were within the recommended South African water quality guidelines for contact recreation as specified by DWAF (1995) except at New Brighton Beach (2 419 total coliforms/100 ml and 1 853 E. coli cells/100 ml) and St. Georges Strand (274 total coliforms/100 ml). Diatoms dominated the phytoplankton and benthic microflora; calanoid copepods dominated the zooplankton and deposit-feeding nematodes dominated the meiofauna in all the beaches with no changes found at polluted beaches.
34
Lopez, de San Roman Blanco Belen. "Dynamics of gravel and mixed, sand and gravel, beaches". Thesis, Imperial College London, 2004. http://hdl.handle.net/10044/1/8106.
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35
Ryan, Tracey E. "The Clean Up Rural Beaches program, environmentalism in action?" Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ40437.pdf.
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36
Canning, Paul John. "Wave breaking on fixed impermeable and mobile permeable beaches". Thesis, University of Brighton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246822.
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37
Tudor, David T. "Aspects of debris pollution at selected Bristol Channel beaches". Thesis, Bath Spa University, 2001. http://researchspace.bathspa.ac.uk/1445/.
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38
Butt, Tony. "Sediment transport in the swash-zone of natural beaches". Thesis, University of Plymouth, 1999. http://hdl.handle.net/10026.1/1784.
Testo completoAbstract (sommario):
Concurrent measurements of velocity, water depth, sub-surface pore-pressure and suspended sediment concentration (SSC) were obtained from the swash-zone o f a macrotidal, dissipaiive (tanP = 0.014), fine to medium grained (dso^ 0.24mm) beach at Perranporth, Cornwall, UK, in low (H^ = 0.8m) to high (Hj « 2.2m) energy conditions. Velocity, pressure and SSC were measured using electromagnetic current meters, pressure transducers and a four-level array of miniature optical backscaner sensors respectively. Results show an infragravity dominated wave field in the swashzone in both high and low energy conditions. In low energy conditions, the ratio between low ( f < 0.05Hz) and high ( f > 0.05Hz) frequency variance increased from 0.6 to 2.3 for both cross-shore velocity and surface elevation, and SSC at z = 1cm increased by a factor of about 5, between just shoreward of the breakpoint (h/hb = 0.6) and the swash-zone (h/hb = 0.2). Swash-zone suspended sediment fluxes at z = 5 to 6cm increased by a factor of about 2 from low to high energy conditions. Low frequency cross-shore velocity skewness values for low and high energy conditions were 0.04 and -0.81 respectively, suggesting an important contribution to offshore transport in high energy conditions, from large, low frequency backwashes manifest in the velocity time-series as low frequency negative skewness. Using 3D velocities from a similar experiment at Muriwai, New Zealand, it is found that TKE/velocity ratios in the uprush were about 1.7 limes larger than in the backwash, suggesting greater turbulence in the uprush. Turbulence and rapid flow reversal are important onshore transport mechanisms, manifest as high frequency negative asymmetry in the velocity time-series. Values for high frequency negative asymmetry at Perranporth were 1.8 times larger in low than in high energy conditions. The influence of inexflltration is investigated using velocity and sub-surface pore-pressure measurements, and a modified Shields parameter, which includes terms to account for the competing effects of stabilisation-destabilisation and boundary layer modification. It is found that there is dominance of stabilisation-destabilisation, resulting in a 4.5% increase in backwash transport and a 10.5% decrease in uprush transport, integrated over a swash cycle. Sensitivity tests show a reversal in this dominance if the median grain size is increased above about 0.55mm, suggesting the transport influence is onshore on coarser grained beaches and offshore on finer grained beaches. Calculations show that hydraulic jumps due to uprush-backwash interaction were about 2.1 times as likely to occur during high than during low energy conditions. Visual observations suggest that more sediment is advected offshore from these jumps in high energy conditions. An antidune ripple field, which enhances transport through increased bed roughness, may also form beneath hydraulic jumps, but this is shown to influence the total dimensionless transport over a 17-min. time-series by less than 5%. Overall results suggest that swash-zone erosion occurs more readily on relatively fine-grained beaches in storms, and accretion occurs more readily on relatively coarse-grained beaches in calm conditions, which is consistent with observations in nature. Large infragravity frequency backwashes manifest as negative infragravity skewness appear to be a key factor in linking enhanced offshore transport in the swash-zone with high energy conditions.
39
Saulter, Andrew Nicholas. "Analysis of infragravity frequency sediment transport on macrotidal beaches". Thesis, University of Plymouth, 2000. http://hdl.handle.net/10026.1/1751.
Testo completoAbstract (sommario):
Many cross-shore sediment transport models use simple treatments of infragravity frequency (0.005- 0.05Hz) processes. For example, infragravity waves have been assumed to provide solely a 'drift velocity' for transport of sediment mobilised by incident frequency waves (0.05-0.5Hz) and be 100% reflected at the shoreline. Furthermore, numerous models calculate broken incident wave heights on the basis of water depth only. This work investigates both the processes underlying infragravity frequency variations in the crossshore velocity field, and the resulting effect of such variations on sediment suspension and transport. Data were selected from three beach experiments in order to compare observations from a range of energetic conditions and positions in the nearshore. Experiments conducted on a dissipative beach at Llangennith, and an intermediate beach at Spurn Head, form part of the pre-existing British Beach And Nearshore Dynamics dataset. The third deployment, at a dissipative site at Perranporth (Cornwall), provided new data for analysis. At Llangennith, high swell waves (significant wave height 3m) were observed, and the measurements come from an infragravity wave dominated saturated surf zone. At Perranponh, locally generated wind wave heights were 2m and measurements came from an incident wave dominated saturated surf zone. Conditions at Spurn Head saw swell wave heights of 1.5m, and observations were made in both an incident wave dominated non-saturated surf zone and the incident wave shoaling zone. Analysis of the data revealed that, in the surf zone, the nature of the infragravity wave field was dependent upon the distribution of energy between higher (>0.02Hz) and lower (<0.02Hz) infragraviiy frequencies. Lower frequency infragravity waves were found to shoal as free waves, while higher frequency infragravity waves were dissipated near to shore on low gradient beaches. Inftagravity wave reflection coefficients showed a dependence on frequency and beach slope (parameterised by the Iribarren number), varied between 50-90% for lower infragravity frequencies, and could be less than 50% for higher infragraviiy frequencies. Incident wave heights were modulated in the shoaling zone with a 'groupy' form. Modulation was also observed in the surf zone, but in the form of individual large waves occurring at low frequency. In the shoaling zone and very close to shore, non-linear interactions occurred between the incident and infragravity components, and calculated phase values between modulated incident waves and infragravity waves indicated a phase shift from a value of less than 180° in the shoaling zone toward 0° close to shore. However, the two signals were not significantly correlated for much of the surf zone. High velocities resulting from a combination of the mean, infragravity and incident wave components drove sediment suspension. Large suspension events occurring at infragravity frequencies were correlated with incident wave groupiness in the shoaling zone, and in high energy conditions with infragravity waves near to the swash zone. Such variations in suspension were related not only to velocity magnitude, but the duration for which a threshold for suspension was exceeded. The bed response to forcing also varied during a tide, possibly as a result of changing bed conditions (e.g. due to bedforms). The infragravity contribution to suspension was independent of the magnitude of suspended sediment concentration, and increased from approximately 30% at the breaker line to 90% in an infragravity wave dominated inner surf zone. The contribution of the infragravity component to transport did not show a similar behaviour, due to phase effects, which produced a reversal in the transport direction between higher and lower infragravity frequencies. Comparison of the observations of sediment transport with energetics predictors identified several cases where the observed transport was qualitatively different from the model prediction as a result of sediment transport thresholds being exceeded at, or for, infragravity timescales.
40
Bradbury, Andrew P. "Response of shingle barrier beaches, to extreme hydrodynamic conditions". Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266585.
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41
Barnes, Timothy. "The generation of low-frequency water waves on beaches". Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319128.
Testo completo
42
Curoy, Jérôme. "Morphological and longshore sediment transport processes on mixed beaches". Thesis, University of Sussex, 2012. http://sro.sussex.ac.uk/id/eprint/39655/.
Testo completoAbstract (sommario):
Mixed beaches, with sediment sizes ranging over three orders of magnitude, are an increasingly important coastal defence on the heavily populated coasts of SE England and N France. Yet longshore transport rates and volumes, important in understanding beach sustainability, remain understudied for such beaches. This thesis addresses the knowledge gap via field investigations of beach profile evolution, active layer measurements and tracer pebble scattering patterns on two macrotidal mixed beaches at Cayeux-sur-Mer (France) and Birling Gap (UK), eastern English Channel. The beach topography data at both sites enabled observation of how reactive the beach profile is to hydrodynamic conditions. Each beach, in different environmental conditions, was found to have a profile that responded extremely quickly to changing hydrodynamics as a result of the combined effects of the High Water Level (HWL) and wave height. The most significant topographical changes are associated primarily with variations in the across-shore position and height of the berm. The research contributes new baseline data to help refine the currently limited understanding of the relationship between depth of disturbance and wave height, wave period, wave direction and the degree of mixture on mixed beaches. Consistent patterns of pebble behaviour were identified during each tidal cycle at different locations on the beach profile. The distance travelled varied with location on the beach profile, with pebbles from the upper beach tending to travel further than pebbles placed on lower parts of the beach. Upper beach pebbles generally showed a clear displacement seaward across-shore whereas lower and middle beach pebbles were affected by shorter across-shore displacements. These displacements are explained by variations in the hydrodynamic conditions, swash flows, groundwater flow, beach slope and grain size. Finally, wave conditions and water level directly influenced the Longshore Sediment Transport (LST) rates. From these results, applying the energy flux approach, a drift coefficient (K) of 0.04 was derived for both sites.
43
Bird, Charlotte C. "Nonlinear interactions of water waves, wave groups and beaches". Thesis, University of Bristol, 1999. http://hdl.handle.net/1983/c8fedc4e-9c73-4791-b1d8-b4ff14646025.
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44
Nel, Petronella. "Physical and biological factors structuring sandy beaches macrofauna communities". Doctoral thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/6146.
Testo completoAbstract (sommario):
Bibliography: leaves 188-199.Previous sandy beach research described beach macrofaunal communities according to the swash exclusion hypothesis (SEH). This hypothesis stated that more species are present on fine grained, flat dissipative beaches due to a more benign swash climate. It suggested that, as beach morphodynamics change to reflective conditions, which is experienced on coarse, steep beaches, few species can survive; these beaches are therefore characterised by lower macrofaunal diversities, abundance and biomass. Furthermore, little proof has been obtained of biological interactions such as competition or predation, and beaches have been described as physically controlled environments. The aim of this investigation was therefore to redifine the SEH in more specific terms, preferably into a form that is experimentally testable, and to find evidence of biological interactions that could be important enough to modify/explain population or community structures. Furthermore, the study aimed to find experimental procedures to serve as alternatives to the previously correlative type approach.
45
Lawrence, John. "Cross-shore morphodynamics of coarse grained beaches and beach/structure interaction : numerical modelling and large scale measurements". Thesis, University of Plymouth, 2005. http://hdl.handle.net/10026.1/1133.
Testo completoAbstract (sommario):
Coastal defence systems are implemented in many countries for the stability of coastlines and prevention of erosion and flooding. The maintenance of such schemes includes the use of 'soft' engineering techniques, which require accurate predictions of sediment transport and profile change. This thesis describes the development of a numerical model for coarse-grained crossshore transport for use in such schemes. The model combines a hydrodynamic model based on weakly non-linear Boussinesq equations, coupled to a sediment transport module and a morphology change module. Studies have been performed on the hydrodynamic and sediment models to assess the performance of the components for this purpose. The 1-D Boussinesq model has been validated with physical wave flume data. The model is shown to provide good predictions for shoaling and breaking waves near the coastline, and is also shown to provide good predictions for the properties of a reflected wave field. The model is then used to perfonn a study on the nature of wave shoaling and reflection with regard to the velocity field, and the development of the velocity skewness pattern is discussed. Recent sediment transport formulae have been reviewed, and a bed-load sediment transport model has been developed. A model for differential transport of different grain sized niaterial has also been introduced. Developed from a river sediment model, this is able to predict sorting of grain sizes over the cross-shore profile. Results of the combined model are shown for natural plane beaches, and for beaches coupled with sea walls. The model predicts reduced erosion patterns for irregular wave fields compared to regular waves, and for mixed sediment composition sea beds compared to homogeneous sea beds. These findings show agreement with features found in previous physical studies. A series of sensitivity studjes has also been performed with respect to hydrodynamic and sediment properties. The model shows a high degree of sensitivity for the profile changes to these parameters. The ability of the model to show predictions for an evolving beach profile subject to tidal water depth variation is also introduced.
46
Atladottir, Audur. "Experimental investigation of wave-induced morphological changes of gravel beaches". Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/27665.
Testo completoAbstract (sommario):
Gravel beaches are widespread around the North-Atlantic Ocean shorelines and can also be found along the coastlines of New Zealand, Russia and the Pacific shore of USA. Over the past decades, researchers in coastal morphodynamics have placed their emphasis on studying sand beaches but gravel material is being used more frequently to nourish eroding sand beaches.
The present thesis aims to advance the understanding of the behaviour of gravel beaches under wave attack. A two-dimensional physical model was developed for gravel beach applications. Regular and irregular waves were considered as well as two different initial beach slopes.
An extensive analysis was performed on the time history of the waves, beach morphology, wave reflection and energy dissipation. Additional geotechnical analysis was also performed in order to identify the characteristics of the beach material. Wave height, wave period, wave duration and initial beach slope were all found to influence beach deformation and wave reflection pattern.
47
Single, M. B. "High energy coastal processes on mixed sand and gravel beaches". Thesis, University of Canterbury. Geography, 1992. http://hdl.handle.net/10092/4381.
Testo completoAbstract (sommario):
The role of high energy events in determining beach morphology on mixed sand and gravel barrier beaches is examined. Analysis of the beach response to high energy events contributes to the understanding of the significance of these events in determining the general and long term function of mixed sand and gravel beach systems. Issues concerned with the contribution of events of differing sizes to the geomorphic character of landforms are an ongoing area of debate in geomorphology. The concepts of magnitude and frequency of events, and thresholds or turning points in the behaviour of geomorphological systems have not been extensively studied in respect of coastal science. These concepts are an underlying theme of the study.
The morphological adjustments of seven beach profile sites along the Wainono Lowland Coast in South Canterbury are analysed using data from repeated profile surveys during a four year period. Excursion distance analysis was carried out on the survey data, and used to examine temporal and spatial variations in response between the study sites.
There were fewer storms during the study period than were expected after consideration of documented historical event occurrence for the area. From an examination of the beach response to the seven storm events that occurred during the study, a semi-quantitative characterisation of high energy events is advanced. Due to the lack of quantitative data describing the oceanographic components of each event, this characterisation was based on the beach response. Three classifications of high energy beach response were adopted. These are 'Destructive' events, which result in overtopping or barrier crest lowering; 'Damaging/Erosive' events, which change the status of the beach by reducing its ability to dissipate wave energy and protect the coastal hinterland; and 'Damaging/Constructive’ events, which result in changes to the foreshore form by net accretion to the profile.
It is proposed that episodes with breaking wave heights in excess of 2.5 metres can be considered as high energy events. Waves of this magnitude produce run-up that affects over half of the beach profile. Damaging events during the study period had wave run-up to at least 4.5 m AMSL. The main differences between damaging and destructive events are in the storm water levels and the storm duration. Higher storm water level set-up occurs for destructive events than for damaging events. Long duration storms (over 20 hours) will result in destructive beach adjustments.
Four factors were noted from this study as being important to the way the beach responds to high energy events. These cue the slope of the foreshore, the presence and dimensions of intermediate berms, the pre-storm volume of beach sediment seaward of the barrier crest, and the sediment composition and structure within the foreshore. Most of the foreshore adjustment occurs in the middle and upper foreshore during high energy events. The antecedent condition of the foreshore, especially the sediment volume content, is an important control on the type of beach response. It was found that profiles with foreshore volumes over 130 m3.m-1 of beach, and foreshore widths greater than 35 metres sustained less damage to the barrier crest than those with lesser dimensions.
A spatial analysis of the field data showed both alongshore and across-shore variations in morphology and morphological adjustments between profile surveys. A quasi-stationary 'slug’, or collective unit of sediment was identified in the field area. The 'crest' of the slug is represented by the region of greatest seaward protrusion, and a foreshore volume in excess of the mean volume over time. The slug 'trough' is the area between crests, which has less than the mean volume over time. The average difference between the slug 'crest' and 'troughs' was 101 m3.m-1 of beach. The difference between the foreshore width at the crest and trough was approximately 20 metres. Movement of the slug of sediment alongshore is a result of the longshore sediment transport processes at work on the mixed sand and gravel beach. The predominant longshore drift for the study area is northwards. Storms generally approach from the south or south east. Due to the low incidence of storms during the study period, there was no evidence of a net northwards passage of the slug through the field area.
The presence of a slug at a site on the coast plays an important role in determining the antecedent morphology of the profile and its ability to dissipate wave energy and protect the coastal hinterland. A site adjacent to a slug crest will present a 'healthier' protection against wave attack than a site adjacent to the trough because there is more sediment available during episodes of erosion, and more beach surface area between the breaking wave and the barrier crest to absorb or dissipate swash energy, therefore reducing the risk of crest erosion or overtopping.
Across-shore variations in process response and sediment shape characteristics were determined from field evidence. The beach profile was divided into six zones. These zones are the 'Backshore', the 'Barrier Crest', the 'Upper Foreshore', the ‘Intermediate Berm', the ‘Interberm Nadir', and the 'Lower Foreshore'. It was noted that no general model of across shore zonation of sediment shape characteristics exists for mixed sand and gravel beaches. This lack of an applicable model has hindered the effective description and comparison of mixed sediment beaches from different parts of the world. Sediment shape data from this study were used to develop such a model. Materials from each zone possess a unique sediment shape signature, which is represented by a frequency histogram of sediment shapes. The model provides a baseline against which other mixed sand and gravel beaches can be compared.
48
Taylor, Gareth Foley. "Management of Sand Beaches for the Protection of Shellfish Resources". Thesis, University of Canterbury. Biological Sciences, 2013. http://hdl.handle.net/10092/8207.
Testo completoAbstract (sommario):
Exposed sand beaches are increasingly under pressure from human population growth and recreation. Activities, such as vehicle driving and horse riding, can pose a significant threat to specialist fauna living in the sediment. Few studies have evaluated how vehicles affect sand beach fauna and none have examined the impacts of horse users on burrowing bivalves.
The research questions addressed were: do vehicles and/or horses on sand beaches impact on intertidal shellfish populations? Following on from this, can management policies mitigate any negative impacts from such activities on sand beaches? This research required an interdisciplinary approach utilising methodologies from coastal geomorphology, biological science and management. The intertidal distribution of the New Zealand surfclam Paphies donacina (southern tuatua) determined seasonally on six exposed surf beaches along Pegasus Bay. The impacts of vehicle and horse users on shellfish survival were experimentally investigated, and novel in situ methods were developed to examine the effects of horses on bivalve survival.
Intertidal tuatua were small (< 30 mm) and shallowly buried. Found approximately 30 m below the last high tide line, they may be exposed to vehicle and horse users. There was a positive linear relationship between the number of vehicle passes and tuatua mortality (% tuatua mortality = 4.8 + 0.23 x number of vehicle passes). On average, horse riding resulted in 36.9% tuatua mortality within a single hoof print, but walking resulted in lower mortality than trotting or galloping. Extrapolative modelling predicted that the long-term presence of these users would be highly detrimental to shellfish. Reducing the temporal frequency and spatial extent of vehicle and horse users on sand beaches could decrease shellfish mortality. The thesis results were used to evaluate current management techniques and provide management options to minimise the potential impacts of beach users on shellfish resources.
49
Van, Wellen Eur Ing Erik. "Modelling of swash zone sediment transport on coarse grained beaches". Thesis, University of Plymouth, 1999. http://hdl.handle.net/10026.1/1761.
Testo completoAbstract (sommario):
A review is presented which assesses the importance of the swash zone as a potential contributor to the longshore and cross-shore transport on steep coarse-grained beaches. Based on this review it is apparent that the swash zone on such beaches forms an important contributor to both the longshore and the cross-shore transport. The review also identifies that the swash zone is neglected in all but a few sediment transport models. In addition, a lack of available shingle beach field data against which to validate existing and new transport models is also reported. Two surf zone integrated equations are presented with the aim of producing simple and physics based formulae relating the total longshore transport (TLT) to the main parameters such as wave height at breaking. In addition, a surf and swash zone inclusive transport formula is developed based on an existing numerical model for the calculation of shingle transport. These formulae, together with existing TLT formulae are evaluated against existing, synthesised and new field data collected during this study. A mathematical model (STRAND) is developed which quantifies sediment transport in the swash zone. The model combines recent advances in the understanding of swash zone dynamics with physics-based predictive transport equations and is computationally efficient. Sensitivity analyses on the model confirm the high potential for transport in the swash zone, both cross-shore and longshore. The STRAND model gives good results when tested against existing data and new field data from shingle beaches at Shoreham-by-Sea and Lancing. Although originally developed for shingle beaches, the model is also validated using data from sand beaches, thus encompassing a wider variety of sediment sizes than many models have used for tests in the past. The swash zone on steep beaches is found to be responsible for as much as two thirds of the volumetric longshore transport. The model also indicated high and rapidly fluctuating cross-shore transport rates, thus contradicting existing transport distribution models. Therefore, sediment transport in the swash zone on steep beaches can no longer be ignored as an important contributor to the overall longshore and cross-shore transport budgets.
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Blott, Simon James. "Morphological and sedimentological changes on artificially nourished beaches, Lincolnshire, U.K". Thesis, Royal Holloway, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396149.
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