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1
Garcez, Faria Antonio Fernando. "Nearshore currents over a barred beach." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA333400.
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Dissertation (Ph.D. in Physical Oceanography) Naval Postgraduate School, June 1997.Dissertation supervisor, Edward B. Thornton. Includes bibliographical references (p. 149-152). Also available online.
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Faria, Garcez, and Antonio Fernando. "Nearshore currents over a barred beach." Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/8729.
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Approved for public release; distribution is unlimited.The objective of this dissertation is to develop numerical models and compare their predictions with data acquired during the DUCK94 experiment in order to improve our physical understanding of the hydrodynamic processes governing the vertical and cross shore distributions of both longshore and cross shore currents over a barred beach. The vertical structure of the mean longshore current is found to be well described by a logarithmic profile and a relationship between bed shear stress and bottom roughness, including the influence of ripples and mega-ripples, was also found. The vertical structure of the mean cross shore current (undertow) is modeled using an eddy viscosity closure scheme to solve for the turbulent shear stress and includes contributions from breaking wave rollers. These models of the vertical profiles of longshore and cross shore mean currents are combined to formulate a quasi three dimensional model to describe the cross shore distribution of the longshore current. This model includes turbulent mixing due to the cross shore advection of mean momentum of the longshore current by the mean cross shore current and contributions from wave rollers
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Cushanick, Matthew Stephan. "Analysis of nearshore currents near a submarine canyon." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FCushanick.pdf.
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Thesis (M.S. in Applied Science (Physical Oceanography))--Naval Postgraduate School, June 2005.Thesis Advisor(s): Thomas H.C. Herbers. Includes bibliographical references (p. 45). Also available online.
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Johnson, David. "The spatial and temporal variability of nearshore currents." University of Western Australia. Centre for Water Research, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0067.
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The nearshore current field, defined here as the residual horizontal flow after averaging over the incident wave period, exhibits variability at a range of time and space scales. Some of the variable currents are low frequency gravity wave motions. However, variable, rotational (in the sense of possessing vertical vorticity) flow can also exist as part of the overall nearshore current field. A field and numerical modelling investigation of these variable rotational currents has been carried out. Drifters, which were developed for surfzone use, enabled measurement of the nearshore current structure; the design and testing of these new instruments is described. Two sets of field measurements, using the new drifters and Eulerian instruments were carried out for conditions with swell perpendicular to a plane beach and in strong longshore currents. In the perpendicular swell conditions, an interesting and well-defined feature of the measured trajectories was the development of transient rip currents. Discrete vortices were also observed. In the longshore current case, trajectories with the longshore current displacement removed had complex meandering paths. Lagrangian data were used to make estimates of length scales and dispersion, both of which provide strong evidence that the current field cannot be due to low frequency gravity waves alone. Under the assumption of equipartition of kinetic and potential energy for low frequency gravity waves, Eulerian measurements of velocities and pressure show significant energy due to non-divergent, rotational flow in both the perpendicular swell and longshore current case. A numerical model that can simulate horizontal flow with a directionally spread, random wave field incident on a plane beach was implemented. The model developed transient rip currents that are qualitatively very similar to those seen in the drifter trajectories from the field. The number and intensity of rip currents in the model depended on the beach slope and incident wave spectra. The energy content and cross-shore flux (and hence transport of material) of the rotational current flow component in the simulated flow fields is comparable to that due to low frequency gravity waves. The modelling also provided some evidence that there may be universal characteristics of the rotational currents. The field results and modelling show that variable rotational currents are ubiquitous in the field even when longshore currents and hence shear waves are not present. The term “infragravity turbulence” is suggested to describe the general class of nearshore hydrodynamics not directly associated with shear waves, which is largely disorganised, but contains well defined features such as transient rips currents and large scale horizontal vortices. The results have important implications in the understanding of the transport of material, including sediment, biological material, pollution, and sometimes bathers, in the nearshore zone.
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Minetree, Courtney M. "Rip channel migration in the nearshore." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Sep%5FMinetree.pdf.
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Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, September 2006.Thesis Advisor(s): Edward Thornton. "September 2006." Includes bibliographical references (p. 39-40). Also available in print.
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Abolfathi, Soroush. "Nearshore mixing due to the effects of waves and currents." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/94785/.
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Analytical, experimental and computational studies were carried out to investigate the mixing and dispersion of neutrally buoyant tracer in the nearshore region due to the effects of waves and currents. The main objective of this study was to quantify the mixing processes in the nearshore region. Theoretical approaches were developed to quantify the contribution of diffusive and dispersive mixing in the nearshore due to wave activity. An analytical model was developed to quantify the diffusive and dispersive mixing mechanisms based on mathematical solutions for the advection-diffusion equation. Mixing under the combined effects of waves and currents were studied through measurement of hydrodynamic and fluorometric tracing experiments from a largescale facility at the Danish Hydraulic Institute, Denmark. The experiments were conducted in a shallow water basin for a range of hydrodynamic conditions covering wave steepness between 2 – 5%. Data from detailed measurements were used to examine the spreading of a solute inside the surf zone and seawards of the breaker region. The overall depth-averaged on-offshore mixing coefficient obtained from the hydrodynamic experimental studies were compared to the mixing coefficients determined from the tracer measurements. It was shown that inside the surfzone, the shear dispersion is the dominant mixing factor, which is almost an order of magnitude greater than the diffusive mixing. The location of the breaker point and the wave height across the nearshore is shown to be important for determining the mixing coefficient. Further detailed spatial and temporal variations of flow hydrodynamics across the nearshore were investigated through a series of laboratory experiments with the use of Particle Image Velocimetry. The experiments were undertaken in a dedicate wave flume at the University of Warwick. Through analysis of the PIV data, new information on the spatial variation of diffusion and dispersion in the shallow water column of the nearshore region was obtained. Flow visualisation of the PIV results identified three distinct hydrodynamic processes during the bore, undertow and the bore/undertow interaction, which were the primary mixing mechanisms in the nearshore region. The temporal variation of dispersion coefficient shows that intense shearing mechanisms exist during wave bore/undertow interactions. The numerical capabilities of Smoothed Particle Hydrodynamics, a Lagrangian, meshless, particle-based method in modelling the nearshore hydrodynamics were explored in this study. The numerical data was used to quantify the mixing processes. By using suitable estimates of turbulent diffusion and cross-shore wave-induced velocity, a theoretical approximation of the overall mixing within the surfzone and seaward of the breaker region can be obtained. A comparison between the theoretical model and previous laboratory and field studies on the nearshore mixing suggests that the mixing is proportional to wave height (H1.5). It is demonstrated that inside the surfzone, the mixing is dominated by the vertical structure of the cross-shore velocity. The pioneering Royal society works of Svendsen & Putrevu (1994) identified the temporally-averaged dispersion, as a function of distance from the shore. Using a combination of experimental, mathematical and numerical formulations, this study has identified and quantified for the first time, the temporal and spatial dispersive mixing processes in the nearshore (over the full wave cycle), within the challenging and complex environment of the surf zone. It has been shown that the cross-shore circulation provides lateral mixing that exceeds that of the turbulence by an order of magnitude inside the surfzone. The turbulence still remains an essential part of the flow since it is the primary driver which through the vertical mixing is responsible for defining the vertical velocity profiles, which then determine strength of the dispersion.
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Osaisai, Evans F. "The interaction between waves and currents in the nearshore zone." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/32434.
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The interaction of waves and currents in the near-shore zone is an area of continuing research where interest derives in particular as a result of various environmental effects from natural phenomena such as storm surges and tsunamis. On time scales longer than that of an individual wave it is necessary to properly evaluate the interaction between waves and currents, using a consistent formulation of mass, momentum and energy within the water column. We describe the formulation of equations describing the mean current flow, driven by the radiation stress field of the waves, an equation for the mean conservation of mass, together with equations describing the conservation of wave action and the kinematics of the averaged wave field. The near-shore zone is often characterized by the presence of breaking waves, and so we develop equations to be used outside the surf zone, based on small-amplitude wave theory, and another set of equations to be used inside the surf zone, based on an empirical representation of breaking waves. Suitable matching conditions are applied at the boundary between the offshore shoaling zone and the near-shore surf zone. Both sets of equation are obtained by averaging the basic equations over the wave phase. In the shoaling zone, we supplement these equations by a simple model of sediment transport, where the bottom is allowed to move in response to the current field of the breaking waves. We use these basic equation sets to re-evaluate previous studies of wave set-up and longshore currents driven by the radiation stress field of the shoaling waves. In particular we extend previous work based on beach profiles with a linear depth dependence to more general beach profiles, including beaches with a depth dependence which varies quadratically with the onshore coordinate, and to beach profiles which approach a constant depth far offshore. We then turn to a situation where the incoming shoaling waves vary periodically in the alongshore direction, and use our basic equation sets to construct a mean current field which likewise varies periodically in the alongshore direction. The outcome, for our set of typical beach profiles, is a description of rip currents. The last part of the thesis examines .a simple model of sediment transport, induced by breaking waves in the surf zone. We show that the previous solutions for wave set-up and longshore currents now become time-dependent as the nearshore zone is eroded by the waves.
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Wang, Baoxing. "Nonlinear interactions of waves and currents with structures in nearshore environments." Thesis, University of Plymouth, 2006. http://hdl.handle.net/10026.1/860.
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In this thesis, nonlinear interactions of waves and currents with structures in nearshore environments are investigated. The emphasis of the research is to model the encountered multiple scales of hydrodynamics (e. g. monochromatic waves and three-dimensional currents) in a numerically efficient and accurate way on a beach and around a structure in the shallow coastal region. The radiation stress and mass flux have been analytically derived by inclusion of higher-order surface elevations. The Boussinesq-type model COULWAVE is used to assess the fully nonlinear wave transformation on a beach. The research unveils the essential roles of the Ursell parameter, Irribarren number and wave steepness described by the local wave height, wave length and bottom slope. Based on the numerical simulations, the radiation stress and the mass flux are statistically formulated. The study has shown that the importance of wave nonlinearity in wave-induced currents and mean water level. The nonlinear transformations of wave profiles produce lower radiation stress and mass flux than linear waves. Case studies suggest the nonlinear formulations produce accurate predictions for mean water levels and current profiles both inside and outside the surf zone on a beach. The new formulations also incorporated in the improved SHORECIRC model to predict current circulation in the vicinity of one or more shore-parallel coastal structures. The simulation accuracies are demonstrated by comparisons to the experimental data from the G8 Coastal Morphodynamics Programme. The model successfully reproduces a large eddy in the region sheltered by a structure. By inclusion of nonlinear integrated wave properties, the predictions of mean water levels and currents have been greatly improved. Analytical, numerical and experimental investigation of oblique wave transmission at low-crested structures is also presented. 7be two-dimensional transmission equation is constructed and validated against the laboratory data of the EU-sponsored project, DELOS. The roles of wave-breaking, nonlinearity, currents and set-up in determining the wave transmission are demonstrated. Wave nonlinearity and wave-induced currents lengthen wave-propagating distance compared to the normal waves, and lead to less transmission on the leeside of a smooth breakwater. Due to the decreased wave amplitudes and mean wave periods after transmission, the phase velocities slow down and cause the change of mean wave direction on the transmission side.
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Brothers, Laura Lee. "Nearshore Sediimentary Pathways and Their Social Implications, Saco Bay, Maine." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/brothersll2006.pdf.
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Shalam, Moinuddin Khaja. "Parallelization of a quasi-3D nearshore circulation model." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-07092004-121009.
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Burnette, Carolina. "Analysis of a Long-Term Record of Nearshore Currents and Implications in Littoral Transport Processes." UNF Digital Commons, 2016. http://digitalcommons.unf.edu/etd/647.
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A seasonal and long-term analysis of the vertical structure of currents in the nearshore is conducted to determine the role of the wind in driving currents and consequently affecting littoral transport processes. Approximately ten years (January, 2002 – October, 2011) of nearshore current profiles are examined using the data collected with an Acoustic Doppler Current Profiler (ADCP) installed off of Spessard Holland North Beach Park located in Melbourne Beach, Florida. Additionally, wind data collected with a directional anemometer from September, 2002, until October, 2008, are used to further characterize the long-term hydrodynamic forcing. With the shoreline oriented nominally 17o west of magnetic north, both the current profiles and the wind vectors have been rendered into longshore and cross-shore components. The water level record from a NOAA tide station located at the Trident Pier at nearby Port Canaveral is utilized in establishing the water depth and conditioning the data for statistical analysis. Monthly mean vertical profiles reveal that during the winter months the surface currents are usually toward the south, and toward the north in the summer. In spring and fall, they are mixed, demonstrating a clear seasonality in both direction and intensity of the longshore current. Subjecting the longshore and cross-shore current data to Empirical Orthogonal Function Analysis reveals that the first spatial Eigenfunction accounts for more than 98% of the variability in the vertical profile of the longshore current, and more than 86% of the variability in the profile of the cross-shore current. However, there is a rotation of the current to the right (clockwise) with the rotation angle increasing and the variance decreasing with depth below the surface. The spiral structure of the water column follows a surface Ekman veering, but for very shallow water. The upper layer of the current is almost aligned with the direction of the wind. Monthly correlations between 2-hour average time series of longshore current and 2-hour average time series of wind speed reveal the seasonal patterns of the wind and longshore current in which the upper layer of the water column is highly correlated with the longshore component of the wind speed for most of the year and slightly less correlated for the lower layer of the water column. Most importantly, on average, wave height (Hmo) is larger when the longshore current is heading to the south (Hmo=0.95 m) than when the current is going to the north (Hmo=0.73 m). Additionally, there is a stronger correlation between southerly directed currents and incident wave energy flux than northerly directed currents and wave energy flux. These results indicate that the net long-term north-to-south sediment transport known to characterize the region is heavily influenced by wind-driven currents.
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Holt, Robert D. "Rip current spacing in relation to wave energetics and directional spreading." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FHolt.pdf.
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Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2003.Thesis advisor(s): Edward B. Thornton, Timothy Stanton. Includes bibliographical references (p. 59-62). Also available online.
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Smallegan, Stephanie M. "Longshore currents near Cape Hatteras, NC." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43719.
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As part of a beach erosion field experiment conducted at Cape Hatteras, NC in February 2010, this study focuses on quantifying longshore currents, which are the basic mechanism that drives longshore sediment transport. Using video imagery, the longshore currents in view of a video camera are estimated with the Optical Current Meter technique and the nearshore morphology is estimated by analyzing breaking wave patterns in standard deviation images.
During a Nor‟easter storm event on February 12 and 13, 2010, the video longshore currents are compared to in situ data and it is found that the currents are most affected by the angle of incidence of incoming waves, increasing in magnitude as the angle becomes more oblique due to a larger component of radiation stress forcing in the longshore direction. The magnitude of the radiation stress forcing, which is at least an order of magnitude larger than the surface wind stress, increases as wave height increases or tide level decreases, which causes more wave breaking to occur. The normalized standard deviation images show wave breaking occurring at an inshore and offshore location, corresponding closely to the locations of an inner and outer bar indicated in survey data.
Using two profiles from the survey data, one profile that intersects a trough and one that intersects a terrace, the video currents are also compared to currents simulated in one-dimension using the circulation module, SHORECIRC, and the wave module, REF/DIF-S, as part of the NearCoM system. Although the simulated currents greatly underpredict the video currents when the flow is only driven by radiation stresses, a mean water level difference between the two profiles creates a longshore pressure gradient. Superimposing a pressure gradient forcing term into the longshore momentum balance that assumes an equilibrium state of the flow, the magnitude of the simulated currents are much larger than the magnitude of the video estimated currents. Using analytical solutions of simplified forms of the mass and momentum equations to determine the effects of accelerations on the flow, it is seen that the acceleration term greatly affects the flow due to the relatively large mean water level difference that acts over a relatively short distance. Therefore, the pressure gradient forcing term is modified to include the effects of accelerations. By including the two-dimensional effects of the acceleration in the one-dimensional model through the modified pressure gradient, the quasi two-dimensional model simulated currents are very similar to the video estimated currents, indicating that the currents observed in the video may be pressure gradient driven.
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McCulloch, Anita. "Nearshore topographic fronts : their effect on larval settlement and dispersal at Sunset Bay, Oregon." Thesis, Thesis (M.S.)--University of Oregon, 2001, 2001. http://hdl.handle.net/1794/10077.
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Leatherman, Stephen B. "Rip Current Generation, Flow Characteristics and Implications for Beach Safety in South Florida." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3884.
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Rip currents are the most dangerous hazard at surf beaches. Rip currents in South Florida have previously not been studied. Beach profiles for three Florida beaches (Miami Beach, Lido Beach, Sarasota, and Pensacola Beach) and one Georgia beach (South Cumberland Island) were chosen for surveying because of their variable sand bar heights. Rip current hazard at each beach was assessed by lifeguard rip rescue and drowning statistics. A relationship was found between sand bar height, beach slope and rip current hazard.
Rip current measurements in South Florida, which involved utilizing GPS drifters, laser rangefinder and drone-imaged fluorescent tracer dye, showed that the speed ranged from 0.1-0.5 m/s, which is fairly slow compared to such measurements undertaken in California and Australia. The effect of rip currents on swimmers was analyzed based on the drag force acting on swimmers and the power they generate to overcome the currents when swimming against them. The drag force and power increase quadratically and cubically, respectively, with the increase of rip current and swimming speeds. Hence, even rip currents of low velocity can be dangerous and swimming against the current should be avoided if possible.
Strong rips in California have been shown to exhibit a circulatory pattern, which could bring a floater back to the safety of a shallow sand bar. Field measurements of rip currents in South Florida clearly defined the flow characteristics of a nearly straight-line current, sometimes deflected to the east-southeast. Therefore, the traditional approach of swimming left or right, parallel to the shore is the best escape strategy, but not against the longshore current if present. A logistic regression analysis was conducted to predict the occurrence of rip currents based on beach conditions. The logistic model showed that wave height, wave period and wind speed were statistically significant factors in rip generation. Rips were found to be most commonly generated by relatively small, non-threatening waves (e.g., 0.6 to 0.9m in height). These physical factors, along with social and safety considerations, pose a significant problem for coastal management.
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Cambazoglu, Mustafa Kemal. "Numerical modeling of cross-shore sediment transport and sandbar migration." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31744.
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Thesis (Ph.D)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010.Committee Chair: Kevin A. Haas; Committee Member: Emanuele Di Lorenzo; Committee Member: Hermann M. Fritz; Committee Member: Paul A. Work; Committee Member: Terry W. Sturm. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Pattrick, Paula. "Larval fish dynamics in the shallow nearshore of Eastern Algoa Bay with particular emphasis on the effects of currents and swimming abilities on dispersal." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005139.
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The larval fish assemblage in the shallow, nearshore region of a proposed marine protected area (MPA) in eastern Algoa Bay, temperate South Africa was investigated. Current velocities and direction and the swimming abilities of late-stage larvae were further assessed to determine potential larval movement to and from the MPA. In total, 6045 larval fishes were collected along two depth contours (~5m and ~15m) in the shallow nearshore of eastern Algoa Bay using stepped-oblique bongo net tows, twice per season for two years (March 2005 – January 2007). These larvae represented 32 families and 78 species. The Gobiidae, Cynoglossidae, Clupeidae, Engraulidae and Sparidae were the dominant fish families. Catches varied significantly between seasons peaking in spring with a mean of 64 larvae/100m3. Preflexion stage larvae dominated catches (75%). All developmental stages of Diplodus capensis, Engraulis capensis, Heteromycteris capensis, Sardinops sagax and Pomadasys species were found in the study area. It appears that these species use the shallow nearshore as a nursery area. Analysis of 12 months (May 2006 – May 2007) data from a bottom-moored Acoustic Doppler Current Profiler within the study area showed that offshore south eastward (39%) and onshore north westward currents (33%) dominated. The south westward current (15%) and north eastward current (12%) occurred less frequently. Current velocity decreased with depth in the nearshore, with a mean velocity of ~29 cms⁻¹ recorded at a depth of 4 m and a mean velocity of ~11 cms⁻¹ recorded at a depth of 14 m. Understanding the dispersal and movement of marine fish larvae in coastal habitats requires knowledge of active swimming abilities. The critical speed and endurance swimming of late stage larvae of two common inshore species occurring in the study area, Diplodus capensis and Sarpa salpa (Family Sparidae), were measured in a laboratory swimming chamber. The mean U-crit value for D. capensis (18.6 cms⁻¹) was similar to that of S. salpa (18.0 cms⁻¹), whereas mean endurance (km swum) was greater in S. salpa (8.4 km) than D. capensis (5.9 km). These swimming abilities exceed the average current velocities observed in the shallow nearshore providing larvae with the ability to greatly alter their passive dispersal trajectories and ultimately influence their distribution in the nearshore.
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Ward, Nikole S. "Investigation of Near-Bottom Current Characteristics Along an Open-Ocean Coast." UNF Digital Commons, 2018. https://digitalcommons.unf.edu/etd/827.
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Near-bottom current data was collected over a period of 8 years at the U.S. Army Corps of Engineers Field Research Facility in Duck, North Carolina. This data set consisted of currents measured up to three elevations above the bottom at deployment depths of 5 meters, 8 meters and 13 meters, as well as continuous real-time wind and wave data collected at the pier. The data was collated, quality checked and analyzed to define a climatology of near bottom currents along the study area using current moments. This data set had previously never been available for analysis due to the large amount of effort required to take old computer files and subject them to rigorous processing and quality control. The analyses conducted in this thesis represent the first ever attempt to analyze this type of data on this scale.
An initial monthly investigation was conducted at the 8-meter site to determine driving forces of mean currents, and a more in depth seasonal investigation was subsequently completed to quantify the relationships between the cross-shore currents and different forcing mechanisms. Once seasonal trends were established relating mean current to incident wave height, wave steepness and wind speed, an examination of some significant historical events within the study was completed to help link cross-shore current behavior to storm events. Three separate nor’easter events and three significant hurricanes (Bonnie, Dennis and Floyd) were found to produce significant cross-shore currents at the study site. Similar to previous nearshore studies, it was found that the occurrence of onshore winds and wave heights greater than about 1.5 meters produce near-bottom mean currents moving in the offshore direction. Alternatively, when winds are blowing in the offshore direction, waves are still propagating onshore, but mean near-bottom currents tend to be directed in the onshore direction.
The importance of vertical current structure within the water column was apparent, even though the instruments’ measurement elevations were all located within the bottom boundary layer. In contrast to the assumption of zero cross-shore velocity at near-coast sites implicit in two-dimensional depth averaged models used in most coastal engineering studies today, it was found that cross-shore near-bottom currents are rarely ever zero. Depth-averaged models inherently assume that currents move as a single block of water throughout the water column. The physical impacts of this misrepresentation of nearshore currents become very significant in predictions of many coastal phenomena, such as storm surge, sediment transport and wave conditions at the coast.
When wave heights exceed 2 meters, mean currents tend to be between 0.2-0.5 meters per second in both the onshore and offshore direction, in the opposite direction of the primary forcing at the surface. In some instances, wave heights are low with strong mean currents while wind speeds are high, indicating the driving force in this situation is wind speed. However, there are cases where wave heights are large and mean current values are relatively low, which requires further investigation. Future work will include investigating phenomena that are related to higher-order odd moments of the current statistics, since they are expected to play a critical role in improved understanding of the physics within the nearshore and are very much needed for predictions of coastal evolution under future sea level rise and potential climate change.
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Johnson, Charley R. "Migration of Dredged Material Mounds: Predictions Based on Field Measurements of Waves, Currents, and Suspended Sediments, Brunswick, GA." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-04082005-145658/unrestricted/johnson%5Fcharley%5Fr%5F200505%5Fmast.pdf.
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Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2005.F. Michael Saunders, Ph.D., Committee Member ; Kevin Haas, Ph.D., Committee Member ; Paul A. Work, Ph.D., Committee Chair. Includes bibliographical references.
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Morris, Bruce J. "Nearshore wave and current dynamics." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA397549.
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Dissertation (Ph.D. in Physical Oceanography) Naval Postgraduate School, Sept. 2001.Dissertation supervisor: Thornton, Edward B. "September 2001." Includes bibliographical references (p. 85-87). Also available online.
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Nizam. "Numerical modelling of three-dimensional wave induced nearshore current." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285609.
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Park, Koo-Yong. "Quadtree grid numerical model of nearshore wave-current interaction." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301255.
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Viljoen, Anél. "Investigation of the nearshore, episodic poleward current in the southern Benguela : a numerical modelling approach." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/6448.
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Includes bibliographical references.Fisheries are of great economic importance on the South African West Coast (the Southern Benguela). The St Helena Bay region is a key nursery habitat for these fisheries because of its retention, upwelling and stratified water column characteristics. However, these characteristics also result in other outcomes such as hypoxia and harmful algal blooms (HAB's) which impact on the habitat suitability character of the system. A nearshore, episodic poleward current has been observed in this region, and it is believed that this current plays an important role in the incidence of HABs as well as hypoxia events. The drivers and dynamics of this nearshore, episodic poleward current have not been clearly understood, nor thoroughly investigated, due to the complexity of the scales and processes. However, the importance of this current in transporting harmful algae from the north into St Helena Bay and its role in habitat hypoxia has emphasized the need to understand its dynamics.
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田中, 和広. "高潮・３次元海浜流および漂砂の解析モデルの構築と実用化に関する研究." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263610.
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Navera, Umme Kulsum. "Development of a model for predicting wave-current interactions and sediment transport processes in nearshore coastal waters." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55916/.
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A two-dimensional numerical model has been developed to simulate wave-current induced nearshore circulation patterns in beaches and surf zones. The wave model is based on the parabolic wave equation for mild slope beaches. The parabolic equation method has been chosen because it is a viable means of predicting the characteristics of surface waves in slowly varying domains and in its present form dissipation and wave breaking are also included. The two dimensional parabolic mild slope equation was discretised and solved in a fully implicit manner, so stability did not create a major problem. This wave model was then embedded into the existing numerical model DIVAST. The sediment transport formulae from Van Rijn was used to calculate the nearshore sediment transport rate.
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Delpey, Matthias. "Étude de la dispersion horizontale en zone littorale sous l'effet de la circulation tridimensionnelle forcée par les vagues : application à la baie de Saint Jean de Luz - Ciboure et au littoral de Guéthary-Bidart." Thesis, Brest, 2012. http://www.theses.fr/2012BRES0081.
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Ce travail de thèse apporte des éléments en vue d’une meilleure compréhension de la circulation et des processus de dispersion associés aux vagues à proximité des plages. Un outil de modélisation numérique opérationnelle a été développé, fondé sur le modèle spectral d’état de mer WAVEWATCH III R et le modèle hydrodynamique 3-D MOHID Water. Le code MOHID a été étendu à l’approche glm2z pour la représentation des interactions 3-D vagues-courant. Les développements théoriques permettant l’obtention des équations glm2z sont rassemblés et détaillés dans ce travail. L’implémentation de ces équations au sein de l’outil de modélisation est exposée. L’outil construit est validé sur deux cas académiques, où est mise en évidence sa capacité à reproduire la solution fournie par des modèles numériques de référence. Par la suite, la modélisation est combinée à des observations in situ pour étudier deux sites de la côte Sud Atlantique française. Ces sites correspondent à des configurations littorales complexes, associant une influence significative des vagues et une stratification haline notable de la colonne d’eau. La confrontation des résultats du calcul 3-D aux mesures fournit des résultats encourageants et apporte des éléments utiles pour la compréhension de la variabilité des courants et des profils de salinité observés. Une baie estuarienne semi-fermée est tout d’abord étudiée. La modélisation y suggère un effet significatif des vagues sur la dispersion des panaches estuariens, susceptible d’impacter la vidange globale de la baie à l’échelle d’un épisode de précipitations. Le second site d’application permet l’étude de la circulation intense induite par les vagues au-dessus d’un système barre/chenal, ainsi que la dispersion des eaux douces introduites par une rivière dans la zone de déferlement. Ce travail fournit finalement un outil de modélisation 3-D pour l’étude de la circulation et du transport sous l’effet de l’ensemble des forçages littorauxThis work aimed at providing a better understanding of nearshore circulation and dispersion processes under the effect of waves. An operational numerical modeling tool was developed, based on the spectral wave model WAVEWATCH III R and the 3-D hydrodynamical model MOHID Water. The MOHID implementation was extended to the glm2z approach for 3-D wave-current interactions. Theoretical developments leading to glm2z equations are gathered and detailed in the present work. The numerical implementation of glm2z equations is described. The model is validated in academic cases, in which the obtained solution is shown to be consistent with that provided by reference numerical models. Both numerical modeling and in situ measurements are then used to study two nearshore environments, located on the French South Atlantic coast. These complex areas combine a significant effect of waves on dynamics and remarkable salinity stratification. Comparison of 3-D model results with field data are encouraging and offers interesting insights for current and salinity profile variability. Dynamics of a semi-enclosed estuarine bay is first studied. Modeling results suggest that waves may have a significant impact on river plumes, leading to a reduction of the global bay flushing during a raining event. The second study site allows the investigation of the intense circulation generated by waves over a ridge and runnel system, and the dispersion of reshwaters introduced in the surfzone by a small river. Finally, this work provides a 3-D numerical modeling tool for the study of the circulation and related transports under the effects of nearshore forcings
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Michaud, Héloïse. "Impacts des vagues sur les courants marins : Modélisation multi-échelle de la plage au plateau continental." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2011. http://tel.archives-ouvertes.fr/tel-00680405.
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Le littoral sableux du Languedoc-Roussillon est un système vulnérable aux risques d'érosion et de submersion. Ces aléas sont liés à la conjonction des facteurs naturels que sont les vagues, vent, élévation du niveau de la mer et apports sédimentaires et sont donc aggravés en période de tempête. En vue d'une gestion des risques, une meilleure connaissance des phénomènes hydrodynamiques de l'échelle littorale à l'échelle côtière est essentielle. Ce travail a conduit à la réalisation d'une plateforme de modélisation numérique composée du modèle de circulation océanique 3D Symphonie, traditionnellement dédié aux échelles régionales et côtières, qui a été modifié pour inclure le forçage par les vagues, modélisées par les modèles Wavewatch III ou Swan, et ainsi étendre sa validité au littoral. Le modèle a été testé sur des cas académiques littoraux. Des mesures sur la plage à double barres de Sète pendant l'hiver 2008-2009, ont également servi à parfaire le modèle qui reproduit ainsi avec succès les caractéristiques des courants en zone littorale : la dérive, les courants sagittaux sur des bathymétries plus complexes et les profils verticaux des courants. Pour valider le modèle à des échelles plus côtières, nous avons confronté ses résultats à des mesures réalisées pendant une tempête hivernale en 2004 aux alentours de l'embouchure de la Têt, mais également sur des tempêtes de 2007 et 2008 dans le Golfe d'Aigues-Mortes. Les courants sont globalement bien reproduits. Les zones d'action des vagues semblent limitées aux zones de profondeur inférieure à 30 m. Notre modèle autorise une reproduction correcte des courants à toutes les échelles et sa nature 3D permet un calcul plus précis de la tension de cisaillement de fond et du courant près du fond, responsables respectivement de la mise en suspension et de l'advection des sédiments.
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Faria, Antonio Fernando Garcez. "Nearshore currents over a barred beach." 1997. http://catalog.hathitrust.org/api/volumes/oclc/38308555.html.
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Lin, Po-Chien, and 林伯謙. "Seasonal variation of nearshore currents along Taoyuan coast." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/u9zq4p.
Full textAbstract:
碩士國立中央大學
水文與海洋科學研究所
106
This study aims to investigate the seasonal variation of the nearshore currents in the coastal zone of Gunging, Taoyuan city. It has the largest and most complete algal reef along Taoyuan coastal in Taiwan. And the sediment transport is affected by the nearshore current. Then the nearshore current research is most important. In order to understand the seasonal variation of nearshore current, we deployed the Acoustic Doppler Current Profiler (ADCP) in the experimental area once a season, and observed the variation of the current and wave for at least two weeks. We also used the numerical model (Delft3d) to simulate the current velocity and the water level. The previous research has indicated that currents in the Taiwan straits is influenced by the tidal current. Therefore, we discuss the nearshore current of total forcing and the residue current (detide). The calculation of the residue current was computed by the observation data (nearshore current of total forcing) minus the simulation result of the tidal current. The result has shown that (1) It has high correlation between the longshore of nearshore current of total forcing and the tide. But when the northeast monsoon gets strong the effect of longshore is more than the tide. (2) The longshore of residue current is strongly correlated with the along shore wind in the experimental area during the whole year. The longshore of residue current also has high correlated with the radiation stress in fall and winter.
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Perkovic, Dragana. "Radar remote sensing of currents and waves in the nearshore zone." 2008. https://scholarworks.umass.edu/dissertations/AAI3322189.
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The relationship between microwave radar and optical video imaging of the nearshore region is studied. The remotely sensed data were used to estimate the longshore currents and the surf zone width. Doppler radar relies on small scale surface roughness that scatters the incident electromagnetic radiation so that velocities are obtained from the Doppler shift of the backscattered radiation. Video relies on texture and contrast of scattered sunlight from the sea surface, and velocity estimates are determined using Particle Imaging Velocimetry (PIV). This study compares video PIV-derived and Doppler radar surface velocities over a 1 km alongshore by 0.5 km cross-shore area in the surf zone of a natural beach. The two surface velocity estimates are strongly correlated (R2 ≥ 0:79) over much of the surf zone. Estimates differ at the outer edge of the surf where strong breaking is prevalent, with radar estimated velocities as much as 50% below the video estimates. Both systems observe a strong eddy-like mean flow pattern over 200 m section of coastline with the mean alongshore current changing direction at about the mid surf zone. The radar and PIV velocities at particular locations in the surf zone track each other well over a 6 hour period, showing strong modulations in the mean alongshore flow occurring on 10-20 minute time intervals. The offshore region in the absence of sufficiently strong wind is sometimes barely visible, while the surf zone always appears very bright in radar backscatter images due to persistent surface roughness produced by breaking waves. The backscatter and coherence radar images were used in conjunction with edge detection filters to estimate the surf zone width from radar data. The surf zone width from video data is calculated using the time-stacking techniques. The comparison of surf zone width over 6 hours showed the rms difference of 8.8 m close to the radar location while the radar had the tendency to overestimate the distance for most of the run. The correlation of two measurements was high at 0.89. At locations farther than 600 m away from the radar the surf zone width rms differences were higher, up to 24 m, while correlation remained high. The differences are attributed to the estimate of the shoreline in radar images due to different scattering properties of wet and dry sand. The good spatial and temporal agreement between the two remote measurement techniques which rely on very different mechanisms, suggests that both are reasonably approximating the nearshore processes.
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(11799693), Paul Boswood. "The evaluation of near-shore current components on macro-tidal beaches: Field analysis and numerical approach." Thesis, 1994. https://figshare.com/articles/thesis/The_evaluation_of_near-shore_current_components_on_macro-tidal_beaches_Field_analysis_and_numerical_approach/17132330.
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With increasing population growths on the Coastal fringes, it is becoming more important to be able to successfully model the coastal processes. To monitor the erosion of the beach profile requires information about the nearshore currents for sediment transport calculations. However, due to the large tidal ranges of macro -tidal beaches, the current will be a complex combination of both wave -induced and tidal current components, with the total current varying with time and distance along the intertidal zone.
In this thesis, FORTRAN programs for the numerical modelling of tidal currents will be developed (WAVECHT and SURFCW respectively). Also, a statistical program (STATCW) for the evaluation of the intertidal currents and
wave conditions from field data will be detailed.
Finally, a preliminary evaluation of the current components at the sub -tidal and inter -tidal zones for a macro -tidal beach on the Capricorn Coast will be made.The evaluation will be based on the subjective interpretation of the reduced
field results from STATCW, with the aid of the prediction models WAVECHT, and SURFCW. Particular focus will be on the relative importance of the longshore tidal current component on the nearshore currents for macro -tidal regions.
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Chang, Lin-Ming, and 張林民. "The Study of Nearshore Current Measuring System." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/70541795328604304061.
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Liew, Khai-Jing, and 廖凱芹. "Numerical simulation of nearshore current along Taoyuan coast." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/e4c2b9.
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碩士國立中央大學
水文與海洋科學研究所
106
Nearshore currents are important for material dispersion and sediment transport, yet, not well understood in Taiwan Strait where complicated forcing mechanisms such as influence from topography, tide, wind, waves, and large-scale current exist. This study was conducted along Taoyuan coast using both numerical model (Delft3d) and observational data. Three Acoustic Doppler Current Profilers (ADCPs) were deployed near-coast from June-July to investigate spatial variations of the current pattern. The model current was performed under different forcing conditions (with and without wind, tide, and wave) with various parameters to examine its sensitivity. Results suggested that the Manning coefficient and breaking index are the two most dominant factors affecting simulation performance for Flow-module and Wave-module respectively. Predicted water level and current velocity are in good agreement with field observations with averaged model skill up to 0.8. Based on the results, current pattern along Taoyuan coast displays remarkable spatial inhomogeneity. Current flow in a region far away from the structure was strongly influenced by wind forcing and always directed to northeastward during the Southwesterly monsoon period. Meanwhile, current flow at region close to the structure is primarily associated with wave forcing. In this region, an anti-clockwise eddy is generated due to the existence of coastal structure. The formation of eddy cause complex interaction of tide, wind and wave-driven current that occasionally offset each other. Further study is required in order to clarify the influence of eddy toward local hydrodynamic. This study is important that can enhance understanding of nearshore current pattern at algal reef region which can aid in future reef conservation.
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Song, Jian Yi, and 宋建毅. "Investigation of the Relationship between Nearshore Current and Wind." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/59727499491233015189.
Full textAbstract:
碩士國立臺灣海洋大學
河海工程學系
95
By overviewing the shortage of nature resources in Taiwan islandwide; or in the other word, by the development of national economic issue the usage and programe of coastal area with coastal secure in order to avoid environment events invaded by the nearshore exploit background survey is necessary to be master planned on the local area, which further includes tides, waves, current and wind. Therefore, in order to look forward for the current issue of time and space distribution is by the use of DGPS (Difference Global Position System) drifter buoys and mooring Acoustic Doppler Current Profiler (ADCP). The pattern of nearshore current is closely related within bathymetry morphology, tidal motion and district wind condition. It is also doubtful to know well the effect of district wind as it was by one means on mooring ADCP or DGPS drifter buoys. Thus, this study, investigation on the field data including the mooring ADCP, DGPS drifter buoys and wind field measured simultaneously near the Yan-Liao coast and the Taipei Harbor. The data support conclusion on the effect of district wind in Taipei Harbor is more significant than those on Yan-Liao coast and if the wind speed gets higher than 3 m/s, the current speed is obviously by the effect of area wind, and increases with the wind.
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Jian-HungTsai and 蔡建宏. "Pixel Time Series Analysis of Nearshore Wave and Current Image." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/16395753077960647143.
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Barrett, Gemma Elizabeth. "Variations in Nearshore Bar Morphology: Implications for Rip Current Development at Pensacola Beach, Florida from 1951 to 2004." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-10038.
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In 2002, Pensacola Beach was identified by the United States Lifesaving Association as being the most hazardous beach in the continental United States for beach drowning by rip currents. Recent studies suggest that the rip currents at Pensacola Beach are associated with a transverse bar and rip morphology that develops with the migration of the bars and recovery of the beachface following an extreme storm. Combined with an alongshore variation in wave forcing by transverse ridges on the inner-shelf, the bar cycle (of bar response and recovery to extreme storms) is hypothesized to create both rip current hotspots and periods of rip activity. However, it is unknown at what stage, or stages, the bar cycle is associated with the formation of these hotspots and the greatest number of rips. To determine how the accretional rip hazard varies in response to the nearshore bar cycle, this thesis will quantify the alongshore variation in the nearshore bar morphology on Santa Rosa Island from 1951 to 2004. Aerial photographs and satellite images are collected for the study area and nearshore features are digitized in ArcGIS and evaluated using wavelet analysis. Specifically, a continuous wavelet transform is used to the identify times and locations when a transverse bar and rip morphology is present or is in the process of developing. The findings suggest that the rip-scale variation in bar morphology (~100-250m) is superimposed on an alongshore variation consistent with the scale of the transverse ridges (~1000m). From the outer bar to the shoreline, and as the bar migrates landward, the variation becomes increasingly dominated by the rip-scale variation.
Hotspots of rip current activity were found consistently between years at Fort Pickens Gate, San Souci, Holiday Inn, Casino Beach, Avenida 18 and Portofino, as clusters of rip-scale variation.
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Chi-RueiLee and 李啓瑞. "Study of the characteristics of Taiwan's nearshore current using SCHISM model." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/rb968u.
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Lu, Ming-Chien, and 呂明杰. "Relative Discussion on Nearshore Current Field Survey by the Free Drift Float." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/97056952574146599806.
Full textAbstract:
碩士國立成功大學
水利及海洋工程學系碩博士班
94
With the increasing of population and the improvement of industrial and/or commercial activities, coastal zone’s usage has been put on more emphasis in Taiwan. Due to the limit territory and ocean surrounding environment, it is necessary to ensure the efficient usage of space and avoid the negative affections caused by human over-developed in coastal zone. So, nearshore current survey and marine data collections such as wind, wave, and depth were indispensable on the characters studing of coastal zone. The relative low price free drift float which is based on GPS positioning and Radio transmission technique carried out the measuring operation instead of using the precious bottom assembled ADCP/current meter to describe the marine flow field characters. Operation risk so, could be reduced by using several free drift floats and few of precious equipment to pick up the current data in marine environment. Theoretically, similar measuring results (false in reality) should be obtained with Eulerian type measuring (ADCP/current meter) and Lagrangian type (free drift float) procedure under the stationary assumption. These studies focus on the wind effect research of interfering the drift tracking and to evaluate the positioning accuracy of this custom-built free drift float. The coastal zone in between southern(Ching Shuei) and northern(Gong Guan) coast of Lan Yang River in YiLan has been selected as the test environment. According to the test results, the free drift float can response the nearshore current field character in 3m/s less of wind velocity and begin gradually the interfering in 1.5m/s up of wind velocity. The average longshore current velocity estimated by both Sato and Eagleson(1965) formula provided a verification datum of current measuring by the free drift float and being identical in speed and, the deviation of 28% in speed has been found which could be affected by wind. Through the measuring data corrected by environmental interfere factors, the free drift float can be applied in field measuring operation and offer the accurate current data as references on coastal engineering planning, designing, evaluating and managing.
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Por-jen, Yang, and 楊博仁. "Numerical Modelling of Topography Changes under Wave-Current Interaction in Nearshore Region." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/26676766224504906987.
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碩士國立臺灣大學
造船工程學系
82
The objective of this paper is to develope a numerical model for changes of sea bottom tography in nearshore region. The comb ined flow field of wave and tides will be considered, and the ef ffect of wave-current interaction are included. The numerical mo del constitutes four parts : (1) prediction model of wave field including current effects. The model is based on the time-depend ent mile-slope equations extended to a parabolic time-independen t equations, and is applicable to the computation of wave deform ation due to combine effects of shoaling, refraction,breaking an d currents. (2)flow field model combing effect of tides, wave, w inds, Corilis force and bottom frictions, Lin and Chiang(1993). (3)estimation model of sediment transports. This model is based on the power model concept, Dibajnia and Watanabe(1987). Soulby et al. (1993) have proposed the computation of ottom stresses an d the rate of energy dissipation in the surf zone is based on ex perimental data ,Mizuguchi(1980). (4)prediction model of sea bot tom tography changes. Some examples of numerical computation are shown, and effects of the wave-current interaction on the nearsh ore waves, currents and beach evolution is discussed.
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Truong, Melanie Khanh Phuong. "Experimental Study on Wave Transformation and Nearshore Circulation on a Variable Bathymetry in Wetlands." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-10157.
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Hurricanes are one of the primary threats to the Texas coastal environment and economy. They generate large wave and storm surges that have caused much damage on the Texas coast in the past. Understanding both the hydrodynamic processes that damage coastal habitats and hurricane hazard and risk are critical to preserve coastal vegetation and quantify its benefits to coastal storm protection. The goal of this project is to quantify the impact of wave attenuation and wave refraction as well as the development of coherent structures in marsh fringes and the formation of a rip current system over wetlands on storm protection. The 3D Shallow Water Wave Basin at Texas A&M University hosted a series of large-scale experiments considering an idealized wetland model to pursue this goal.
Study of the marsh geometry of the Texas coast was done in order to scale the experiments to the size of the Haynes Laboratory 3D-Water Wave Basin using a Froude and a Reynolds scalings. Particularly, averaged size and idealized shape of marsh segments in the area of Dalehite Cove in Galveston Bay were considered. Three sets of different wave conditions and water levels were tested to approximate different intensities of storm surge. Identical tests with both vegetated and non-vegetated marshes were run to compare the influence of the vegetation in storm conditions, and three different spacings between marsh segments were tested.
In the basin, normally incident regular waves were generated at three water circulation structures. Data analysis allows the determination of the impact of discontinuous marsh segments on wave attenuation and wave refraction. Coherent structures such as rip current and the circulation pattern were analyzed to study the change in the flow field during passage of the waves.
The experimental measurements were able to describe the wave transformations over the marsh segments. The influence of coastal wetlands was identified to affect the hydrodynamic process and reduce the total wave energy which is dissipated and redistributed by vegetation. The presence of the mounds induced an important decrease in the wave height, in addition to the damping of the waves by the vegetation stems. The variation in spatial coverage of the wetland model has been shown to highly affect the flow dynamics by generating offshore directed flow in the channel and onshore directed flow on the marsh mounds. This experimental approach provides a further understanding of flow dynamics by waves and surge in wetlands, at a large scale.
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Johnson, Angela Michelle. "An investigation of the distribution and abundance of ichthyoplankton and juvenile benthic fishes in relation to nearshore hypoxia within the Northern California Current system." Thesis, 2012. http://hdl.handle.net/1957/34734.
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Nearshore hypoxia within the Northern California Current (NCC) system is a seasonal phenomenon caused by coastal upwelling and occurs mainly during late-summer and early fall. The effects of low oxygen levels on fish and invertebrate communities, particularly during early-life history stages, however, are poorly known for this area. I investigated the effects of hypoxia on the density, community structure, vertical and horizontal distribution of fish larvae and juveniles, as well as body condition of juveniles, along the central Oregon and Washington coasts during the summers of 2008 - 2011. During this sampling period, bottom dissolved oxygen (DO) values ranged from 0.49 to 9.85 ml l�����, and the number of hypoxic (e.g., < 1.4 ml l�����) stations sampled was low compared to 2002 and 2006 (only 54 sampling stations for the ichthyoplankton study out of 493, and only 12 stations out of 90 for the benthic juvenile study). From the ichthyoplankton study, I found that the overall density of fish larvae increased as bottom-DO values increased; however, the effect on individual species density was limited. Between 44.65 ��N and 46.00 ��N (~Florence, OR ��� Astoria, OR), fish larvae altered their vertical distribution when bottom-DO was low by rising in shallower water layers.
From the benthic juvenile study, I found that English sole (Parophrys vetulus), butter sole (Isopsetta isolepis), speckled sanddab (Citharichthys stigmaeus) and Pacific sanddab (Citharichthys sordidus) dominated the catch with annual variation in abundances. Species composition, abundance and length had strong relationships with depth. Species abundance for English sole (< 75 mm), speckled sanddab (<100 mm) and Pacific sanddab also increased with increased bottom-DO. However, the body condition of butter sole (< 75 mm) and of large speckled sanddab (���100 mm) increased with decreased bottom-DO.
Overall my research elucidates important patterns of larval and juvenile fish distribution within the NCC during summer. In both studies I have found a limited effect of DO on abundance, distribution and community assemblages. Variables other than DO, such as depth, season and location, dominated the explained variance of the intervening multivariate and univariate analysis. However, due to the paucity of samples during hypoxic events, continued monitoring of nearshore larval and juvenile species over varying hypoxic conditions is necessary for understanding the impact of hypoxia on these communities and subsequent adult populations.Graduation date: 2013