Measurements and Three-Dimensional Modeling of Nearshore Circulation on a South Carolina Beach

A numerical modeling system for simulating nearshore surf zone conditions and tidal processes is presented and evaluated with in situ data. The modeling system is comprised of the Regional Ocean Modeling System (ROMS v 3.0), a three-dimensional numerical ocean model, coupled with Simulating Waves Nearshore (SWAN), a spectral wave propagation model. The system has been modified with a new vertical distribution of radiation stress terms for applications in very shallow waters. The model performance is evaluated by comparing simulations to hydrodynamic data (wave height, direction, longshore and cross-shore currents) collected in the surf zone in northern South Carolina, U.S. Model results have been analyzed to discern the variability in three-dimensional and depth-averaged cross-shore and longshore velocities due to changing wave height, wave direction and tidal stage. Overall, the model shows good correlation to observed data and it is found to be capable of reproducing typical flow patterns observed due to depth-induced wave breaking. An implication for sediment transport applications on beaches with tidal variability is also discussed

Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Ocean Modelling 47 (2012): 65-95, doi:10.1016/j.ocemod.2012.01.003.The coupled ocean-atmosphere-wave-sediment transport modeling system (COAWST) enables simulations that integrate oceanic, atmospheric, wave and morphological processes in the coastal ocean. Within the modeling system, the three-dimensional ocean circulation module (ROMS) is coupled with the wave generation and propagation model (SWAN) to allow full integration of the effect of waves on circulation and vice versa. The existing wave-current coupling component utilizes a depth dependent radiation stress approach. In here we present a new approach that uses the vortex force formalism. The formulation adopted and the various parameterizations used in the model as well as their numerical implementation are presented in detail. The performance of the new system is examined through the presentation of four test cases. These include obliquely incident waves on a synthetic planar beach and a natural barred beach (DUCK’ 94); normal incident waves on a nearshore barred morphology with rip channels; and wave-induced mean flows outside the surf zone at the Martha’s Vineyard Coastal Observatory (MVCO). Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK’ 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from Garcez-Faria et al. (1998, 2000). Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using non-dimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction, bottom stress, breaking acceleration, horizontal advection and horizontal vortex forces dominate the momentum balance. The simulation results for the bar / rip channel morphology case clearly show the ability of the modeling system to reproduce horizontal and vertical circulation patterns similar to those found in laboratory studies and to numerical simulations using the radiation stress representation. The vortex force term is found to be more important at locations where strong flow vorticity interacts with the wave-induced Stokes flow field. Outside the surf zone, the three-dimensional model simulations of wave-induced flows for non- breaking waves closely agree with flow observations from MVCO, with the vertical structure of the simulated flow varying as a function of the vertical viscosity as demonstrated by Lentz et al. (2008).The first two authors were supported by a NOAA/IOOS Grant (Integration of Coastal Observations and Assets in the Carolinas in Support of Regional Coastal Ocean Observation System Development in the Southeast Atlantic) and a cooperative agreement between U.S. Geological Survey and University of South Carolina as part of the Carolinas Coastal Change Processes Project. Also G. Voulgaris was partially supported by the National Science Foundation (Awards: OCE-0451989 and OCE-0535893)

Alongshore momentum balance analysis on a cuspate foreland

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 118 (2013): 5280–5295, doi:10.1002/jgrc.20358.Nearshore measurements of waves and currents off Cape Hatteras, North Carolina, U.S.A, are used to investigate depth-averaged subtidal circulation and alongshore momentum balances in the surf and inner shelf region around a cuspate foreland. Data were collected on both sides of the cape representing shorefaces with contrasting shoreline orientation (north-south vs. northwest-southeast) subjected to the same wind forcing. In the nearshore, the subtidal flow is aligned with the local coastline orientation while at the cape point the flow is along the existing submerged shoal, suggesting that cape associated shoals may act as an extension of the coastline. Alongshore momentum balance analysis incorporating wave-current interaction by including vortex and Stokes-Coriolis forces reveals that in deep waters surface and bottom stress are almost in balance. In shallower waters, the balance is complex as nonlinear advection and vortex force become important. Furthermore, linearized momentum balance analysis suggests that the vortex force can be of the same order as wind and wave forcing. Farther southwest of Cape Hatteras point, wind and wave forcing alone fail to fully explain subtidal flow variability and it is shown that alongshore pressure gradient as a response to the wind forcing can close the momentum balance. Adjacent tide gauge data suggest that the magnitude of pressure gradient depends on the relative orientation of local coastline to the wind vector, and in a depth-averaged sense the pressure gradient generation due to change in coastline orientation even at km length scale is analogous to the effect of alongshore variable winds on a straight coastline.The experimental work was funded by the Carolinas Coastal Processes Project, a cooperative study supported by the US Geological Survey. Additional support during data analysis and preparation of this manuscript was provided by the National Science Foundation (award: OCE-1132130).2014-04-1

Tidal asymmetry and residual circulation over linear sandbanks and their implication on sediment transport : a process-oriented numerical study

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): C12015, doi:10.1029/2007JC004101.A series of process-oriented numerical simulations is carried out in order to evaluate the relative role of locally generated residual flow and overtides on net sediment transport over linear sandbanks. The idealized bathymetry and forcing are similar to those present in the Norfolk Sandbanks, North Sea. The importance of bottom drag parameterization and bank orientation with respect to the ambient flow is examined in terms of residual flow and overtide generation, and subsequent sediment transport implications are discussed. The results show that although the magnitudes of residual flow and overtides are sensitive to bottom roughness parameterization and bank orientation, the magnitude of the generated residual flow is always larger than that of the locally generated overtides. Also, net sediment transport is always dominated by the nonlinear interaction of the residual flow and the semidiurnal tidal currents, although cross-bank sediment transport can occur even in the absence of a cross-shore residual flow. On the other hand, net sediment divergence/convergence increases as the bottom drag decreases and as bank orientation increases. The sediment erosion/deposition is not symmetric about the crest of the bank, suggesting that originally symmetric banks would have the tendency to become asymmetric.Funding for this work was provided by the U.S. Geological Survey as part of the SC Coastal Erosion Study and by the South Carolina Sea Grant Consortium (grant V169). Additional support for one of the authors (G. Voulgaris) was provided by the Office of Naval Research (Southeast Coastal Ocean Observing Systems) and by the National Science Foundation (award OCE-0451989)

Analyzing the effect of socio-political context on tourism: perceptions of young tourists in Greece, Portugal and Israel

International crises that affect tourism, such as terror attacks, political unrest, and economic crises have become more frequent, and their influence has become broader. The influence of such extreme events depends on their salience in the tourists' awareness. Hence, it is important to understand the mechanisms underlying tourists' selection of travel destinations, especially their perceptions of crisis-related events and the impact of the sociopolitical and economic context in their countries of origin. The current study examined how the socio-political and economic context in the home countries of potential young tourists affected their selection of travel destinations. The objective was to elucidate how the salience of various crises (economic and political) in the tourists' perceptions, due to their experiences at home, color their construal of destinations affected by similar hazards and influence their travel intentions. The study focused on student tourists from Israel, Greece, and Portugal. Today about a fifth of international tourism is based on young people, especially students. These countries were chosen since Greece and Portugal are in the midst of economic crises. In addition, Greece and Portugal have experienced political instability, while Israel has security-related problems (including terrorist incidents). In 2013, a total of 648 students, responded to a questionnaire that included questions concerning attitudes and risk perceptions regarding travel to destinations with various risk hazards as well as socio-demographic details. The results indicate that over half of the Israelis intend to visit Greece or Portugal. The majority of the Portuguese intend to visit Greece, while less than a third of them intend to visit Israel. About half of the Greeks intend to visit Portugal, and most of them do not intend to visit Israel. The results indicate that greater perceived importance of economic crises mitigates the intention to travel to destinations with economic crises for tourists from origin countries that are also marked by economic crises, such as Greece and Portugal. However, for tourists from Israel, a country with a relatively stable economy, issues related to the economy barely affect their intention to travel to the other two countries. The findings also suggest that Greeks and Portuguese who are highly concerned about political unrest are unlikely to select Israel as a tourist destination. In addition, strong apprehension regarding terrorism impedes the intention to travel to destinations marked by terrorist incidents, such as Israel. The current research contributes to the existing literature by highlighting the impact of travelers' personal previous experience with crisis on their risk perceptions and in turn on their intentions to travel to countries with similar risks. Therefore, in a world where such incidents are on the rise, understanding tourists' risk perceptions and behavior and the factors influencing their destination-related decisions are crucial for countries that wish to increase the numbers of incoming tourists.info:eu-repo/semantics/publishedVersio

Factors shaping young tourists' intentions to travel to Greece, Israel and Portugal: Universal or idisyncratic perceptions of young Greeks, Israelis and Portugese?

Tourism constitutes an important branch of economy, especially in countries experiencing economic crisis and harsh socio-political events. The current study compares the intention of young people from three different countries – Greece, Israel and Portugal - to travel to two selected destinations. For each country of origin the other two countries were the destination of interest. This research examined the factors affecting young tourists' intention to travel to different destinations assuming that those determinants depend on the country of origin as well as on the destination country. The sample comprised of 648 students: Israelis (277), Portuguese (200), Greeks (171). The research questionnaire was distributed in Israeli, Greek and Portuguese academic institutions in 2014. The results indicate that over half of the Israelis intend to visit Greece or Portugal. The majority of the Portuguese anticipate visiting Greece, while only 32.5% expect to visit Israel. Among the Greeks nearly 50% intend to visit Portugal and do not intend to visit Israel. The study showed that the main factors affecting the decisions of young Portuguese to travel to Israel were: the image of Israel, the perceived risk of traveling to a country with political unrest and the number of trips abroad. The main factors affecting the decisions of young Greeks were the perceived risk of traveling to a country with political unrest and Israel's image. Israelis' decision to travel to Greece was affected by their image of Greece; the Portuguese also took into account the perceived risk regarding economic situation. For Israelis, considering Portugal as a traveling destination was related to the destination's image. The Greeks were affected by the number of Facebook friends and the Innovation, Entrepreneurship and Digital Ecosystems perceived economic risk. This research suggests that the socio-economic, political context of the country of origin and of the tourist destination plays an important role in young tourists' travelling-related decision-making.info:eu-repo/semantics/publishedVersio