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Wave-current Interaction and Its Impact on Contaminant Transport
Primary Investigator:
Meng Xia - NOAA/GLERL
Co-Investigators:
Dave Schwab - NOAA/GLERL
Dmitry Beletsky - NOAA/GLERL
Eric Anderson - NRC
Hongyan Zhang -
University of Michigan - CILER*
Executive Summary of Rationale
This project is designed to develop a three-dimensional coupled Wave-current model that can simulate and predict wave effects on the structure of currents, water level fluctuations, sediments and the bacteria, algae and distribution in the Grand Haven River and adjacent beach areas. The project will calibrate the model with the help of observational data. The projects will help the Physical oceanographer, Biological Oceanographer to know the wave effect to Great Lakes. Ultimately, we hope to gain insight regarding 1) the wave effect on the structure of the currents 2) the wave effect on bacterial distribution 3) the properties of plume structure under the influence of waves.
Proposed Work
Current/Ongoing
- Implement and Test the Wave-Current Interaction Model of FVCOM.
- Application of FVCOM to the Grand Haven Area to simulate the wave effect on currents and hydrodynamics calibration with horizontal ADCP data from 2008
- Set up the FVCOM ecological model to simulate the plume dynamics and contaminant/algae transport under the influence of the wave effect.
- Set up EFDC to simulate the current, contaminant and larval transport under the wave effect.
- Compare these two estuary coastal ocean models to the future physical-biological interaction of Great Lakes Area.
- Demonstrate the possibility of real-time application of the hydrodynamic-biological area of Grand Haven areas on Lake Michigan.
Scientific Rationale
Waves have a very important effect on the current structure. Waves play an important role in the transfer of momentum and energy across the air-sea interface and strongly impact currents and the nearshore ecosystem. Although the waves reduce their significant wave heights (SWH) when they reach the shallow water, they significantly impact the coastal zone via exacerbated currents, erosion and damage. When waves encounter the near shore current, there can be subsequent penetration, absorption, reflection, or refraction of the wave field. As waves move into near shore regions, the subsequent energy gradients cause additional near shore circulation. In additional, previous findings indicate that currents will reduce (increase) significant wave height when waves propagate following (opposing) the current direction (Liu, 2006).
Longuet-Higgins and Stewart [1960, 1961] developed the theory of conserved wave-current interactions and they introduced radiation stress into the governing equation. The bottom stress, which is a function of wave-current interaction in the near bottom layer when the water depth is sufficiently shallow for wave effects to penetrate to the bottom [Signell et al., 1990]. It is also believed that wind waves can indirectly affect the coastal ocean circulation by enhancing the wind stress [Mastenbroek et al., 1993]. Xie et al. [2001, 2003] studied wave-current interactions through both surface and bottom stresses and found that wind waves can play a significant role in the overall circulation in coastal regions. Previous studies of (Xie et al, 2008) showed that it is important to incorporate the wave-current interaction effect into coastal circulation in the application of Charleston Harbor, SC, especially with the consideration of wave-induced wind stress and 3-D radiation stress in coastal ocean modeling which could significantly improve the correctness of the model simulation.
The proposed project concerns the nonlinear interaction of waves and currents on the coupled physical-biological environment, in particular the wave effect on the current and its subsequent contaminant and bacteria transport. Waves are also important in various processes, such as the re-suspension and transport of sediments. The currents resulting from this wave induced circulation many times control the transport of parameters of interest to water quality. The interplay of the non-linear processes involved requires the use of numerical modeling to understand the distribution of energy in the near shore and describe the transport processes accurately.
The Grand River is the largest tributary entering Lake Michigan. The combination of a major River, relatively simple shoreline geometry, and low-slope, regular bathymetry makes this an ideal site for developing, testing, and refining a nested-grid hydrodynamic model. There are also several highly utilized and often contaminated beaches in this area.
The FVCOM Model (Chen et al, 2003) serves as the base and main model for this system. The system still needs some additional testing. The wave-current interaction section of the numerical model will be used simulate the physical/ecological environmental variables for the Grand Haven and adjacent water body. Variables include the three dimensional velocity field, the three-dimensional temperature field, the water level distribution and the wind wave height, length, period, and direction, and resuspension, transport, and deposition of bottom sediments based on wave and current conditions. Simulations are made on a high resolution horizontal unstructured grid with about 10 vertical slices comprising the vertical grid. More extensive evaluations have occurred in hind cast comparisons with field experiment data, including the ADCP real time current observation (Figure 1). As a result of these testing activities, we should know the wave–current interaction effect on the physical-biological process ain the Great Lakes, at least at the Grand Haven region.
Figure 1 GLERL ADCP real time current observation
In the long term, this project could help the Great Lakes Forecasting System (GLFS, Bedford and Schwab, 1994; Schwab and Bedford, 1994) which has been developed to provide short-range operational (regularly scheduled) predictions of such conditions for the open waters of the Great Lakes.
The information needs of typical resource managers are for water quality data; data not yet predicted or available in forecast form. In additional, the water quality forecasts require knowledge of both point and non-point sources. This initial proposed research program will focus on the process study of point source loadings of nutrients and bacteria into coastal environments from particular rivers and its impact on beach closures.
In addition to FVCOM (Figure 2), EFDC will also be used for calculation of Grand Haven wave-current interaction hydrodynamic-eutrophication circulation (Figure 3). Over the past 5 years, the FVCOM model has been adapted for use in the estuary and coastal region (Chen et al, 2008a; Chen et al, 2008b; Chen et al, 2008c). The model is based on the three-dimensional, nonlinear Navier-Stokes equations. It employs a terrain-following vertical coordinate (sigma coordinate) to provide high vertical resolution even in shallow areas. EFDC is very similar to the FVCOM and it has strong record of application to the estuary and coastal ecological modeling (Ji et al., 2001, Shen and Haas, 2004; Park et al., 2005, Yang and Hamrick, 2005).
Figure 2 High-resolution unstructured FVCOM grid of Grand River for coupled wave-current modeling with resolved complex geometry of rivers and shorelines.
Figure 3 High-resolution unstructured EFDC grid of Grand River for coupled physical-ecological modeling with resolved complex geometry of rivers and shorelines.
Both numerical modeling efforts and integrated field activities are proposed to characterize the study region and test model adequacy. A modeling hierarchy mainly based upon the FVCOM wave-current model which can better simulate the near shore dynamics of wave-current interaction and circulation which could greatly help beach advisories and the future possible real-time short-range forecasts. Additional benefits will also include the potential to forecast other water quality variables of interest and the general applicability of this modeling system to other sites in the Great Lakes. EFDC serve as a substitute and additional numerical tool for this aim as well as the comparison of EFDC model. The application of EFDC model could be a step to get some additional funding from EFA agency and Michigan State Environmental Agency.
In additional to simulate the wave effect to the current circulation. Biological sub-models will also be turned on first-order decay processes as part of this year's plan to test the influence of wave effect. Furthermore, based upon the success of this modeling system various scenarios will be tested to determine the extent of their ecological consequences. Should the ecological outcomes be well constrained then it will simplify our meeting of the second program objective. We will initially focus on developing a generic modeling system for coastal managers employing visualization techniques to aid interpretation and ease of use.
Results from the whole-lake simulations will be used to specify the open water boundary conditions for the Grand Haven simulations. All modeling modifications and implementations will be performed so as to maximize the ease of applying it to other Great Lakes sites in the future. The success of this proposed research will depend upon the ability of the model to accurately track the contaminant plumes and describe their interaction with coastal dynamics.
Overall, out main tasks solve the following problems:
- Is the wave effect important to the near shore circulation at the Grand Haven Area?
- Could contaminant/algae transport be influence by the wave effect?
- Is there any difference by using structure and unstructured grid?
- What is the difference of plume dynamics between Great Lakes freshwater Region and Ocean salt water parts?
- Will wave influence the plume dynamics at the near shore region?
Governmental/Societal Relevance
The wave-current based hydrodynamics-eutrohpication modeling system will be useful to all users of the Great Lakes coastal waters who require the information of temperatures, currents, water levels, and waves. Wave and current physical processes have a major impact on environmental, chemical, and biological processes and influence many other types of user activities, such as water supply management, waste water management, power plant sittings, shipping, recreational and commercial boating and fishing, shoreline erosion and redistribution of sedimentary material. Planners and managers responsible for any part of the Great Lakes ecosystem that is affected by wave induced nearshore circulation, such as transport of toxic material or nutrient enrichment processes. The wave current modeling system of lake waves, water levels, water temperatures, and currents are expected to provide ecologist with a significant source of new information which should lead to considerable improvements both in the accuracy and efficiency of ecological marine forecasts for the Great Lakes.
The integrated suite of wave-current based hydrodynamic models could serve the Great Lakes connecting waterways, including emergency responses to toxic spills/releases; management of contaminated sediments through improved knowledge of transport mechanisms; prediction of pathogen movement affecting contamination at public bathing beaches; predictions of conveyance to optimize commercial transportation of goods and material; protecting drinking water from contaminant inflows; improving safety for recreational boaters and fishermen; and improved support for search and rescue operations. Both FVCOM and EFDC have ecological modeling sub model as well as the dye transport model. While each of these uses may require slight additions or modifications to the model, certain basic model properties or outputs are common to many or most uses. The model framework will be designed to allow linkages of hydrodynamic processes to water-quality, biological productivity, and sediment-transport models. The models will be based on open source codes and held in the public domain to facilitate their long-term distribution, use, and expansion.
Relevance to Ecosystem Forecasting
This project should contribute to the development of experiment forecasts of nutrient/contaminant distribution, especially under the effect of the wave. Very few studies have been test the nearshore wave-current interaction to the ecological dynamics. This project could serve a pilot studies for the Great Lakes, even in the world. Within the frame of this project, two ecological models will be applied to Grand Haven in the first step. Although we only test the nutrient/contaminant transport in FY2009, the model will be continue to improve to simulate the ecological process and the future forecasting in the whole Great Lakes as well as the current application of Grand Haven. While we will not focus on developing predictive capabilities for ecological process in FY2009 plan, we are confident that our model implementing will improve forecasting in the future.
Cited References
Bedford,K. W, Schwab, D.J, (1994) The Great Lakes Forecasting System: An Overview Rumer (eds), Hydraulic Engineering ’94, Proceedings of the Conference, ASCE
Chen, C., H. Liu, and R. Beardsley (2003), An unstructured grid, finite-volume, three-dimensional, primitive equations ocean model: Application to coastal ocean and estuaries, J. Atmos. Oceanic Technol., 20(1), 159 – 186.
Chen, C., P. Xue, P. Ding, R.C. Beardsley, Q. Xu, X. Mao, G. Gao, J. Qi, C. Li, H. Lin, G. Cowles, and M. Shi, (2008a), Physical mechanisms for the offshore detachment of the Changjiang diluted water in the East China Sea, J. Geophy. Res., 113, C02002, doi:10.1029/2006JC003994.
Chen, C., Q. Xu, R. Houghton and R. C. Beardsley, (2008b). “A model-dye comparison experiment in the tidal mixing front zone on the southern flank of Georges Bank”. J. Geophys. Res., 113, C02005, doi; 10.1029/2007jc004106
Chen, C, J. Qi, C. Li, R. C. Beardsley, H. Lin, R. Walker and K. Gates, (2008c). “Complexity of the flooding/drying process in an estuarine tidal-creek salt-marsh system: an application of FVCOM (DRAFT)”. J. Geophys. Res. doi: 10.1029/2007jc004328, in press.
Ji, Z., Morton, M.R., Hamrick, J.M., 2001. Wetting and Drying Simulation of Estuarine Processes Estuarine. Estuarine Coastal and Shelf Science 53(5), 683-700.
Liu, huiqing 2006 Analysis and modeling of wave-current interaction http://www.lib.ncsu.edu/theses/available/etd-10192006-144755/
Longuet-Higgins, M. S. and R. W. Stewart, (1960) Changes in the form of short gravity waves on long waves and tidal currents. J. Fluid Mech., 8, 565-583
Longuet-Higgins, M. S. and R. W. Stewart, (1961) The changes in amplitude of short gravity waves on steady non-uniform currents, J. Fluid Mech., 10, 529-549
Mastenbroek, C., G. Burgers, and P. A. E. M. Janssen, The dynamical coupling of a wave model and a storm surge model through the atmospheric boundary layer, J. Phys. Oceanogr., 23, 1856– 1866, 1993.
Park, K., Jung, H., Kim, H., and Ahn, S., 2005. Three-dimensional hydrodynamic-eutrophication model (HEM-3D): application to Kwang-Yang Bay, Korea. Marine Environmental Research 60, 171– 193.
Schwab, D.J. and K.W. Bedford, (1994) Initial implementation of the Great Lakes Forecasting System: a real-time system for predicting lake circulation and thermal structure. Water Poll. Res. J. Can., 29(2&3), 203-220.
Shen, J., Haas, L., 2004. Calculating age and residence time in the tidal York River using three-dimensional model experiments. Estuarine, Coastal and Shelf Science 61, 449-461.
Signell, R. P., et al., (1990). Effect of wave-current interaction on wind-driven circulation in narrow shallow embayments, J. Geophys. Res., 95, 9671– 9678
Xie, L., Wu, K., Pietrafesa, L.J., Zhang, C., (2001) Anumerical study of wave–current interaction through surface and bottom stresses: wind –driven circulationinthe South Atlantic Bight under uniform winds. J. Geophys. Res. 106(16), 841–885.
Xie, L., Pietrafesa, L.J., Wu, K., (2003) A numerical study of wave–current interaction through surface and bottom stresses: coastal ocean Response to Hurricane Fran of 1996. J. Geophys. Res. 108(C2), 3049. doi:10.1029/2001JC001078.
Xie, L., Liu, H., Peng, M., (2008) The effect of wave–current interactions on the storm surge and inundation in Charleston Harbor during Hurricane Hugo 1989 Ocean Modelling (20) 252–269
Yang, Z., Hamrick, J.M., (2005) Optimal control of salinity boundary condition in a tidal model using a variational inverse method. Estuarine Coastal and Shelf Science 62, 13-24.
*Link leads off GLERL's website
