Peter Bacopoulos

Sea-Level Rise Impact on a Salt Marsh System of the Lower St. Johns River

AbstractThe impact of sea-level rise on salt marsh sustainability is examined for the lower St. Johns River and associated salt marsh (Spartina alterniflora) system. A two-dimensional hydrodynamic model, forced by tides and sea-level rise, is coupled with a zero-dimensional marsh model to estimate the level of biomass productivity of S. alterniflora across the salt marsh landscape for present day and anticipated future conditions (i.e., when subjected to sea-level rise). The hydrodynamic model results show mean low water (MLW) to be highly spatially variable with a SD of ± 0.18 m and mean high water (MHW) to be less spatially variable with a SD ± 0.03 m. The spatial variability of MLW and MHW is particularly evident within the tidal creeks of the salt marsh. MLW and MHW are sensitive to sea-level rise and respond in a nonlinear fashion (i.e., MLW and MHW elevate by an amount that is not proportional to the level of sea-level rise). The coupled hydrodynamic-marsh model results illustrate the spatial hetero...

Unstructured mesh assessment for tidal model of the South Atlantic Bight and its estuaries

Localized truncation error analysis with complex derivatives was applied to compute target element sizes for tidal flow in the South Atlantic Bight (SAB) and its estuaries. An existing finite element mesh was used to generate a tidal solution that is fed into this code, which assesses the truncation error and drives it to a more uniform value through selective mesh gradation, and results in a target element size distribution for the SAB and its estuaries. The target element size distribution is compared to the element size distribution of the existing mesh. The code prescribes larger than the initial elements for the shelf and deeper waters and smaller than the initial elements for the shallow-water region. Along the coast, elements similarly sized as the initial elements are prescribed at the inlets, but larger elements are prescribed between adjacent inlets.

Hydrodynamics of the 2004 Florida Hurricanes

Abstract Hagen, S.C.; Bacopoulos, P.; Cox, A.T., and Cardone, V.J., 2012. Hydrodynamics of the 2004 Florida hurricanes. We studied the hydrodynamic response caused by the four major hurricanes that struck Floridas coasts in 2004: Charley, Frances, Ivan, and Jeanne. A large-scale, shallow-water-equation model was applied so as to simulate wind and tidally driven hydrodynamics from the deep ocean into the shelf and coastal waters of Florida. Hurricane Ivan served as the calibration case, where the adjusted parameter was the wind drag coefficient. We identified an “increased” wind drag coefficient to perform best and suggest it as a first approximation to the wave contribution to the hydrodynamics. The increased drag coefficient is offered to the consulting and/or forecasting communities, who are frequently without wave-modeling resources, as a pragmatic approach to approximate for waves. Hurricanes Charley, Frances, and Jeanne serve as the validation cases in which the increased wind drag coefficient was applied. Analysis was performed by inspection of maximum water-surface elevations, which are interpreted in terms of shelf and bay dynamics for the west coast hurricane cases (Charley and Ivan) and in terms of channel hydraulics for the east coast hurricane cases (Frances and Jeanne). We conclude that the broad shelf off Floridas west coast allows the storm tide to accumulate along the open coast and that the embayments further magnify the storm tide, and that the Atlantic Intracoastal Waterway along Floridas east coast is effective in propagating storm tide, where we show compartmentalization of the storm tide in the Indian River lagoon as caused by the flow impediment of the causeway abutments.

Hydrodynamic Modeling of Hurricane Dennis Impact on Estuarine Salinity Variation in Apalachicola Bay

ABSTRACT Huang, W.; Hagen, S., and Bacopoulos, P., 2014. Hydrodynamic modeling of Hurricane Dennis impact on estuarine salinity variation in Apalachicola Bay. Hurricane Dennis made landfall in Florida on 10 July 2005 and caused a storm surge of 2.4 m in Apalachicola. Field observations of salinity, winds, and river inflows are available at a few stations in the bay during the hurricane event. Presented in this paper is a numerical modeling study that investigates the effects of Hurricane Dennis on estuarine mixing and transport. A previously calibrated three-dimensional (3D) estuarine hydrodynamic model was further validated by the field observations of salinity and water levels during the hurricane event. A large-scale storm-surge model was used to provide storm-surge hydrographs at the five estuarine boundaries for the 3D estuarine model. This model integration proved successful with the results indicating that the model predictions of storm-surge hydrographs and salinity match well with observations. Model predictions of spatial distributions of salinity and current fields are presented to demonstrate the fresh-saline water mixing at different times of the storm-surge event. Results indicate that the hurricane-induced storm surge caused substantial increase of salinity in the bay. Majority saline water entered the bay from the east during the storm surge event. Salinity at the oyster reef, Cat Point in the eastern bay area, is more sensitive to the increased water levels caused by storm surge than another oyster reef, Dry Bar, in the western bay area.

Tidal Spectroscopy of the Lower St. Johns River from a High-Resolution Shallow Water Hydrodynamic Model

The nonlinear distortion of the astronomic tide in the Lower St. Johns River is investigated. Computed tidal elevations are analyzed at various locations within the Lower St. Johns River. The modeling approach first evaluates the boundary condition applied at the open ocean with regards to it providing a complete description of the tidal elevation, followed by numerical experimentation and a tidal constituent analysis that examines the effects of finite wave amplitude, advection, and bottom friction towards distorting the tide as it propagates upriver. The distortions caused by each nonlinear source are presented in both the time and frequency domains. Analysis at observation stations reveals a river tide with more coastal characteristics near the mouth and with more considerable distortion upriver. The spectroscopy of the astronomic tide for the Lower St. Johns River is established in terms of a custom set of tidal constituents.

Dynamic Considerations of Sea-level Rise with Respect to Water Levels and Flooding in Apalachicola Bay

ABSTRACT Bacopoulos, P., and Hagen, S.C., 2014. Dynamic considerations of sea-level rise with respect to water levels and flooding in Apalachicola Bay. An examination of sea-level rise impacts on water levels and flooding extent in Floridas Apalachicola Bay and the nearby region was carried out using forcing conditions from Hurricane Dennis under multiple sea-level rise scenarios. A comparison of the modeled water levels at the inlets of the bay was conducted to determine if the trend in water levels at the inlets was linear or nonlinear in relation to increasing sea-level rise. Hydrodynamic simulations for five scenarios were performed, including a present-day (control) scenario reflecting current sea levels and four possible future sea-level rise scenarios. Water level distributions and flooding throughout the bay with either dynamic or static sea-level rise were compared, and the effects of nonlinearity in the hydrodynamic responses were measured using a normalized nonlinearity index. This analysis highlights the importance of considering the two-dimensional spatial distribution in water levels when examining the consequences of sea-level rise, as analyses of hydrographs at point locations can overlook important subtleties throughout the domain. The results of this study provide a fuller representation of possible responses of Apalachicola Bay to sea-level rise, taking into account the combined context of water-level nonlinearity and flooding extent.

Sea-Level Rise Effects on Hurricane-Induced Salinity Transport in Apalachicola Bay

ABSTRACT Huang, W.; Hagen, S.C.; Bacopoulos, P., and Teng, F., 2014. Sea-level rise effects on hurricane-induced salinity transport in Apalachicola Bay. Salinity is an important indicator for estuarine ecosystem. Estuarine salinity can be affected by hurricane and sea-level rises. In this study, hydrodynamic modeling study has been conducted to investigate the effects of sea-level rise on hurricane-induced salinity in Apalachicola Bay. By using the dataset for the Hurricane Dennis occurred in July, 2005, model simulations were conducted under different sea-level rise scenarios. Results from model simulations show the effects of sea-level rise on the estuarine salinity transport during different phases of the storm surge. Generally, the increase of water level by either storm surge or sea-level rise results in the intrusion of majority saline sea water from the east to the west through East Pass. Salinity at two oyster bars responds to the storm surge and sea-level rise differently because Cat Point is located in the east and Dry Bar is in the west of the river mouth. In Cat Point, sea-level rise can cause substantial increase of salinity because it is located between the river mouth and East Pass. Salinity at the peak of the storm surge reaches 30 ppt even without sea-level rise. While salinity at the end of the storm surge reduces to about 20 ppt under no sea-level rise condition at Cat Point, it substantially increases to 30 ppt in response to a sea-level rise of 0.2 m. However, in Dry Bar, salinity is less sensitive to the sea-level rise and the storm surge. At the peak of the storm surge, salinity in Dry Bar is 30 ppt, 28 ppt, 30 ppt., under SLR 0.2 m, 0.5 m, and 1.2 m, respectively. However, near the end of the storm surge, salinity is 22 ppt, 22 ppt, and 27 ppt under 0.2 m, 0.5 m, and 1.2 m SLR conditions, respectively. This indicates that, after the storm surge, salinity in Dry Bar can recover to the normal range (below 26 ppt) if sea-level rise is less or equal to 0.5 m.

Tidal Simulations for the Loxahatchee River Estuary (Southeastern Florida): On the Influence of the Atlantic Intracoastal Waterway versus the Surrounding Tidal Flats

Two-dimensional tidal flows within the Loxahatchee River estuary (Southeastern Florida) are simulated in order to assess the effects of incorporating the Atlantic Intracoastal Waterway (AICWW) versus including the surrounding tidal flats in the computational domain. The region of interest is modeled with three variations of an unstructured, finite-element mesh, including a localized mesh with and without tidal flats, and an extended mesh that describes the AICWW. Phase and amplitude errors between model output and historical data are quantified in terms of water surface elevations at five locations within the Loxahatchee River estuary to assess the relative performance of the various computational meshes. While it is shown that the surrounding tidal flats provide some benefit to the numerical model, the hydrodynamics resulting from the inclusion of the AICWW results in a more significant improvement in the simulated water levels—an important modeling consideration that is commonly disregarded in practice. The application of additional boundary conditions enables for both hydrodynamic factors (AICWW; surrounding tidal flats) to be included in the numerical simulation. As a corollary, velocity residuals are computed on a domain-wide basis to reveal significantly different net circulation patterns within the Loxahatchee River estuary, depending on the level of description of the AICWW, and further demonstrate the importance of including the AICWW in the numerical model.

Integrated Hydrologic-Hydrodynamic Modeling of Estuarine-Riverine Flooding: 2008 Tropical Storm Fay

AbstractSoil and water assessment tool (SWAT) and advanced circulation (ADCIRC) models were integrated to generate a hydrologic (SWAT)–hydrodynamic (ADCIRC) model applicable for flood prediction in...

Florida's Intracoastal Waterway in a Storm Surge Setting: Longwave Physics and Mesh Resolution

This paper works toward the study of the longwave physics and the mesh resolution needed for the modeling of storm surge in north Florida, namely, how to incorporate Florida’s Intracoastal Waterway, which narrows and becomes highly constricted (only 100 m wide), into a finite element mesh that contains the full coastal domain including the floodplain. Numerical storm surge experiments are conducted using various domain definitions (finite element meshes) of Florida’s Intracoastal Waterway with Hurricane Dora (1964) as the test-case scenario. Questions examined in the paper are: (i) is there a frictional component to Florida’s Intracoastal Waterway, that is, does the overall storm surge, as it’s propagating over the Intracoastal and into the floodplain, feel any impact because of the Intracoastal’s presence; and (ii) how does resolving Florida’s Intracoastal Waterway in the finite element mesh affect simulated storm surge conveyance along the Intracoastal, and thus, transmission of storm surge to adjacent water bodies?