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In this paper, one-dimensional, unsteady and cross-sectionally averaged Saint-Venant-type model was used for flow modeling in tidal river network of Pearl River Delta, China. A three-staged approach is employed for the solution of river network hydrodynamic equations. To model the influence of an accident release of high cadmium concentration in upstream of Pearl River Delta, a cadmium model in considering the exchange between water and sediments was coupled with the hydrodynamic model. The river network was divided into 582 calculated river reaches with length ranging from 500 m to 2500 m. With a time step of 10 min, the hydrodynamic model and cadmium model were respectively calibrated and verified. Modeled stage/discharge and cadmium concentration were found matching well with the measured data. The roughness of river reaches in Pearl River Delta was calibrated to be 0.016 to 0.044. Several scenarios of accident release of pollutants with high cadmium content were modeled. Distribution of cadmium concentration at selected sections under accident release in river network of Pearl River Delta were given. The modeled results put forward a base to deal with pollution accident in Pearl River Delta where important water source sites are located.
This paper presents the application a 3D hydrodynamic model (EFDC) to Little Manatee River (LMR) estuary located in the southwestern of Tampa Bay. Model boundaries were specified by field observations of hourly observations for model simulations, including freshwater inputs, tides, winds, salinity and temperatures at bay boundary, and air temperatures. By comparison with observations of water levels, salinity, and temperature at several river stations, the hydrodynamic model for LMR river system has been satisfactorily calibrated and verified to support water resources and estuary ecological studies. Salinity intrusions in the river system were investigated under typical low, average, and high flow conditions.
The numerical model DynaRICE and its application to ice jam formation and release is presented. The model is a two-dimensional coupled flow and ice dynamic model. The ice dynamic component, which includes both the internal ice resistance and boundary friction on ice motion, uses a Lagrangian SPH method. The hydrodynamic component of the model uses a streamline upwind finite element method, which is capable of simulating trans-critical flow conditions. The model is validated with field observed ice jam data. The phenomena of ice jam formation and release dynamics are examined using the validated model.
In general, the flow in a wide open-channel is two-dimensional in the region away from the sidewall. However, the same flow over a mobile bed is three-dimensional, showing a series of pairs of counter-rotating vortices over longitudinal bedforms. This is due to the cellular secondary currents formed over the entire cross section. The initiation mechanism of such cellular secondary currents has not yet been clearly demonstrated. The interaction between the pre-existing vortex created by the sidewall and the bottom sediment is thought to be related to the initiation of those secondary currents. The presence of the free surface and sidewall as well as the non-uniformity of sediment particles are also known to strengthen the cellular secondary currents. In the present paper, turbulent open-channel flows over sand ridges and troughs are numerically simulated. The Reynolds averaged Navier-Stokes equations are solved with the non-linear k-ε model. This turbulence model was selected mainly due to its speed in computation. Mean flows and turbulence statistics are presented. The simulated secondary currents clearly showed upflows and downflows over the ridges and troughs, respectively, and the simulated results are compared with experimental data sets available in the literature. The modeling presented here is an important step in investigating the initiation mechanism of cellular secondary currents in a wide open-channel.
In some physical model experiments, it is necessary to use distorted models. It is difficult, however, to build in an optimal degree of distortion into the models to ensure a closer degree of similarity between the model and the prototype. Three-dimensional (3D) numerical simulation is used in this paper to model experiments with a straight channel under different distorted scales. The calculated results of stream-wise, lateral and vertical velocities and sediment concentration along the vertical direction are shown by comparing the deviations of the velocities and sediment concentration between the distorted model and a normal one. Generally the discrepancy between the distorted model and the normal in stream-wise velocity is acceptable, while in vertical and transverse directions, the velocity shows differences. Concerning sediment concentration and channel bed deformation, the effect of the distorted scale is mainly related to two different similarity criteria. The similarity ratio between the turbulence diffusion velocity and gravity settling velocity can reproduce better results of sediment concentration along the vertical direction. The better bed deformation results come, however, from the similarity ratio between the averaged flow velocity and gravity settling velocity.
The Bras d'Or Lakes (BdOL) is a land-locked estuarine system in central Cape Breton Island. Nova Scotia, Canada. Recent outbreaks of waterborne diseases at several sites in the BdOL have decimated shellfish populations and threaten its unusual biodiversity. Assessing the potential for spread of invasive pathogens is a priority for management. A nested-grid hydrodynamic modeling system is used to simulate the three-dimensional (3D) circulation and temperature-salinity distributions for summer 1974, when currents and hydrographic measurements suitable for model calibration were made at several locations. The modeled 3D velocity fields are then used in Eulerian-Lagrangian transform to study the spatial patterns of retention and dispersion of passive particles, as a proxy for the spread of disease by water flow in the estuary. Probabilities of transfers (connectivity) among 10 sub-domains of the BdOL are calculated from the statistics of the 3D particle trajectories and portrayed in a transition matrix. The model results demonstrate that the hydrodynamic connectivity among the several small bays in the western portion of the BdOL (ranging from 0.1% to 13.5%) is much weaker than those among the main basins (16% to 62.4%) at monthly time scales. Restriction by narrow passages between the small bays and the main basins reduce connectivity among populations and their habitats, but the effect is partially offset by density-driven flows associated with freshwater inputs at the land boundaries. The model can be used to guide epidemiological surveys and generate testable hypotheses of disease spread and species invasions within the ecosystem.
Hydrodynamic and sediment transport modeling is important to the analyses of the aggradation and degradation of a river system, the sediment management in a reservoir, and the study of downstream effect on the coastal sediment. This paper presents a development of a three-dimensional hydrodynamic and sediment transport model to investigate the variation of sediment concentration in Shihmen Reservoir in Taiwan under typhoon induced flood events. The fundamental equations that govern fluid flows and sediment concentration are the Reynolds-averaged Navier-Stokes (RANS) equations and sediment transport equation. Model equations are solved by using an implicit, finite-difference scheme in a curvilinear and vertically stretched coordinate system. A case study of Shihmen Reservoir utilizing the present flow and transport model is presented. The upstream flow-rate conditions are obtained from the data recorded during the 2005 Typhoon Haitang. The computed results clearly reflect the three-dimensional feature of the velocity field in the reservoir. The predicted time-varying water surface elevation during the 140-hour flood event agrees well with measured data. For the sediment concentration, only limited measurements in the domain are available. When comparing with the measured data, the present model is capable of providing reasonable predictions on the rising trend of sediment concentration during the period that flow rate increases, however, the model overestimates concentration values at the recession stage when the measurements of sediment concentration are shown in the decreasing trend. Other results showing the time variation of the velocity vectors and sediment concentration at selected vertical layers are presented and discussed.
Hydropower reservoirs impounded by high-head dams exhibit complex circulation that confuses the downstream migrating salmon and limits successful collection and passage of fish. Fish passage engineers attempt to modify the hydrothermal behavior at reservoirs through structural and operational modifications and often use hydrodynamic simulations to guide their actions. Simulation of key hydrothermal processes such as (a) development of a stable two-layer stratified system, (b) density-driven currents over a reservoir length scale, and (c) discharge hydraulics near the power generation and fish collection intakes requires highly specialized models applied at differing temporal and spatial scales. A staged modeling approach is presented that uses external coupling of models at varying temporal scales and spatial resolution to simulate the entire hydraulic regime from the mouth of the reservoir at the upstream end to the discharge at the dam. The staged modeling approach is illustrated using a case study where structural modifications were evaluated to improve reservoir stratification and density-driven currents. The model results provided input and valuable insight in the development of a new structure design and configuration for effective fish collection near the forebay of a high-head dam.
The Hydrological Simulation Program – FORTRAN (HSPF) in interface with the Better Assessment Science Integrating Point and Nonpoint (BASINS) was used to evaluate the impact on hydrology components of the Luxapallila Creek watershed due to different land use/land cover (LU/LC) databases. The 1,770-km2 watershed is located in Alabama and Mississippi. Simulation of the watershed processes were tested at the hillslope and at the watershed outlet for the period between 1985 and 2003. Three LU/LC databases were evaluated: the GIRAS, the Moderate Resolution Imaging Spectroradiometer (MODIS), and the National Land Cover Data (NLCD). The three LU/LC databases showed that more than 70% of the watershed area is covered by forest. Forest areas produced small changes among databases. Forest cover mechanisms were the main source of water losses. The model was more sensitive to daily time steps than annual periods when the MODIS and NLCD datasets were compared to the GIRAS database. In general, the MODIS dataset showed a higher variation on hydrology simulations than the NLCD database when both LU/LC databases were compared to the GIRAS database.
This paper presents the mathematical formulation of an integrated surface-subsurface-overland model for flow and transport of thermal energy and salinity. The model contains three major components: a 3D surface water module, a 2D overland module, and a 3D subsurface module. The surface water module simulates flow and transport in the main channel of rivers/estuaries based on the 3D Navier-Stokes equations with or without hydrostatic assumptions. The moving free surface is explicitly handled by solving the kinematic boundary condition equation and a moving grid method with a node-repositioning algorithm is used to track the deformation of the water surface. The surface water transport module solves the energy equation for spatial-temporal distributions of temperature and the mass transport equations for the salinity field. The numerical solution is obtained using the finite element method or the mixed Lagrangian-Eulerian (particle tracking) and finite element method. The overland module solves the 2D simplified diffusive wave equations, and the transport equations for temperature and salinity using the finite element method. The groundwater module adopts the modified Richard's equation, the Darcy's law, and the transport equations to model the flow and transport of temperature and salinity through saturated-unsaturated porous media using the finite element method. The integrated model also enables the dynamic surface-subsurface, surface-overland, and overland-subsurface interactions through the couplings of flows and transports at the interface. The integrated model has been tested and applied to Loxahatchee Estuary for the investigation of floodplain habitat hydroperiod in the Northwest Fork of the river.
St. Louis Bay estuary is a vital water body in the Mississippi Gulf Coast Region and greatly affects the water quality in the Mississippi Sound. As the first step of total maximum daily load (TMDL) study, a hydrodynamics model was developed by integrating Hydrological Simulation Program Fortran (HSPF) and Environmental Fluid Dynamics Code (EFDC). In this application the EFDC model was configured to simulate time-varying surface water elevation, velocity, salinity, and water temperature. The HSPF was applied to compute the fresh water discharge from the upstream watersheds. The model reasonably simulated the tidal range and phase. The simulated water temperature and salinity showed good and fairly good agreement with observations. The calculated correlation coefficients between computed and observed velocity were lower compared with those for water level, temperature, and salinity, but the magnitudes of simulated velocity were found to be in the range of observed data. The wind data was found to have strong impacts on velocity simulation by modeling verification tests. Near the study area, there is wind data available only at one station, which has been applied to the entire modeling domain. The lack of high-resolution wind data makes it very difficult to simulate the velocity distribution well. It is anticipated and recommended that the development of this model be continued to synthesize additional field data into the modeling process.
Saint Louis Bay Watershed is a coastal watershed located in southern Mississippi, which composes two basins: Jordan River Basin and Wolf River Basin. Two land use/land cover (LULC) datasets: the Geographic Information Retrieval and Analysis System (GIRAS) and the National Land Cover Data (NLCD) are applied on these two basins to simulate the hydrologic and water quality parameters by using the Hydrological Simulation Program - FORTRAN (HSPF) and the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS). The difference of GIRAS dataset and NLCD dataset for the Saint Louis Bay represents the LULC change from 1977 to 1992. The area percentages of Forest Land and Urban or Built-up Land decrease for both these two basins. However, the area percentages of Wetlands and Barren Land increase. The Rate of Soil Erosion has a great increase in the area changing from other LULC classifications to Barren Land. As a result of the loss of vegetation and the aggravation of soil erosion, the Total Outflows of Sediments has a great increase, which deteriorates the water quality. However, other hydrologic and water quality parameters including Streamflow, Water Temperature, and Dissolved Oxygen, in contrast, result in insignificant changes.
By means of the physical process-based modeling approache to computing coastal and estuarine hydrodynamic and morphodynamic processes, an integrated model system was developed to simulate tides, waves, currents, winds, sediment transport, and morphological changes in coastal and estuarine regions. This paper presents an overview of this integrated morphological process modeling system consisting of modules for simulating random wave deformations, tidal and shortwave-induced currents, sediment transport and morphological changes. The individual modules included in the integrated model system were validated by simulating hydrodynamic and morphodynamic processes in laboratory experiements and field study cases. An example for model application to an estuary is presented to demonstrate the model's effectiveness in simulating comprehensive impacts of combined storm waves, typhoons (or hurricanes), river floods, sediment transport, and morphological changes in its coastal and estuarine area. This modeling system provides engineers and researchers with an efficient and effective numerical software package to facilitate better coastal erosion protection, flood and inundation prevention, coastal strom water management and infrastructure protection against hazardous storms, typhoons, and hurricanes.
A two-dimensional numerical model employing a fully transformed σ-coordinate system in the vertical direction is developed to analyze the scalar transport in an estuary. For a preliminary step of developing the numerical model, the influence of a coordinate transformation on the accuracy of the numerical simulation is investigated by comparing the computational results in both z- and σ-coordinates with analytical solutions. In addition, the numerical errors due to the transformation are investigated according as whether the diffusion term is fully derived or not. The numerical accuracy attributable to the full transformation is examined by comparing predicted results with those of the model employing only the partial transformation in a simply sloped topography. Finally, the numerical model developed in this study is applied to the Keum River estuary in Korea, for a salinity intrusion simulation. The calculated results showed good agreement with the observed field data, both of which clearly indicate that the tidal effect on the salinity intrusion are clearly discerned in the estuary.
Charlotte Harbor is one of major estuaries in Florida. The upper portion of the estuary receives freshwater inflows mainly from the Peace and Myakka Rivers. To study the hydraulic interactions between the Upper Charlotte Harbor (UCH) and its major tributaries, a multi-block model was used to simulate hydrodynamics and salinity transport processes in a simulation domain that includes the UCH, the Lower Peace River (LPR), the Lower Myakka River (LMR), the Shell Creek, and a portion of the Myakkahatchee Creek. In the modeling study, the simulation domain is split into a 3D simulation block and several 2DV blocks. The 3D block includes the UCH and the most downstream portions of the LPR and LMR, while the 2DV blocks contain the rest of the tributaries. All the blocks are patched together without any overlaps. The coupled model solves 3D RANS equations for the 3D block, but laterally averaged RANS equations for the 2DV blocks that consist of narrow and braided tributaries. Both 3D and 2DV sub-models use an efficient semi-implicit, flux-based finite difference method. The dynamic coupling is facilitated using a free-surface correction method, in which matrixes for the water surface correction in both the 3D and 2DV sub-domains are solved simultaneously after they are merged together. Model simulations demonstrated that the multi-block model is an efficient tool for simulating hydrodynamics in a very complex environment and the model application to the LPR-LMR-UCH system is successful.
The Pearl River, one of the seven largest rivers in China, drains into the South China Sea. To simulate the transport and distribution of non-saturated suspended sediments in the Pearl River Estuary, a three-dimensional sediment transport model coupled with a three-dimensional hydrodynamic model has been developed. The model was validated by comparing simulation results with suspended sediment concentrations measured on July 25–26, 1999 at four sites within the study area. The validation indicated that the model can simulate the transport and distribution of suspended sediments reasonably well. The simulated surface suspended sediment concentrations matched the satellite images qualitatively. It was found that suspended sediments in the study area exhibit strong vertical stratification, and sediment concentrations near the river gates are generally lower in the surface layer of the water column and increase with water depth while the minimum concentrations may be observed in the middle layer of water column where fresh and salt waters meet together. Generally, suspended sediments discharged from each river gate are carried by currents along the coast toward the southwest. During both high- and low-tide periods, the horizontal distribution of suspended sediment concentrations clearly demonstrates peaks adjacent to the river gates and a spatially decreasing trend from the northwest to the southeast in the study area. Contours of suspended sediment concentrations often migrate toward the ocean at low tides outside of most river gates. All these findings indicate that suspended sediments in the Pearl River Estuary primarily have terrestrial sources.
The Snohomish River is one of the largest rivers to discharge into to the Puget Sound estuarine system. The tidal circulation, mixing and salt intrusion processes in the Snohomish River estuary are complex due to the presence of a large intertidal region, multiple distributary channels, and a sharp gradient of bottom elevation from the estuary to the fjordal depths of Puget Sound. To accurately simulate the tidal mixing and salt intrusion in such a complex system, a high-resolution model grid in both horizontal and vertical directions is required to represent the details of the geometry and bathymetry changes in the study domain. In this paper, a finite volume, unstructured coastal ocean model, FVCOM, was used to simulate the estuarine physical processes specific to the current state of the Snohomish River estuary, which consists of a number of dike-trained channels forming a uniquely braided system. The model was calibrated against observed data for a neap-spring tidal cycle collected during fall of 2006. Model simulations were carried out to study the tidal mixing, baroclinic flow, tidal residuals, salinity stratification and intrusion in the Snohomish River. Model results demonstrated that successful simulation of the physical processes in a complex braided estuary are feasible with a finite volume, unstructured model such as FVCOM.
A hydrodynamic model of St. Joseph Bay, FL has been developed based on a finite-element circulation model. We have tested the model against predicted astronomical tides and field measurements of water levels at three locations inside and outside the bay. Good agreement has been found, including the correct prediction of the change of the tidal regime from diurnal to mixed tides and the high-frequency oscillations in St. Joseph Bay excited by meteorological forcing. The validated hydrodynamic model was employed to partition the tidal prism of St. Joseph Bay in the event of a breach at Stump Hole north of Cape San Blas and to estimate the flushing through a new inlet at Stump Hole, or the portion of tidal prism controlled by a breach. The existing methodology for inlet stability analysis of a single-inlet system is extended to this two-inlet system if stump Hole is breached by a tropical cyclone. A ten-step procedure has been developed for the breach stability analysis, which has three major components. First, the empirical relationships of inlet geometric parameters were employed to develop a series of possible breach configurations. Second, the validated hydrodynamic model was modified to accommodate the new inlet and numerical simulations were carried out to determine the hydraulic conditions corresponding to each inlet configuration. Third, the computer model results of this two-inlet system were combined with the empirical relationship of tidal prism and inlet cross-sectional area for equilibrium inlets to predict the stable inlet configuration and the fate of a breach using the maximum velocity curve in an Escoffier-type diagram. Similar to the use of an equilibrium beach profile in the design of beach nourishment projects, the concept of an equilibrium inlet and the empirical relationship for stable inlets provide a useful tool to predict the fate of a breach in a multi-inlet, multi-tidal-regime system.
Environmental Fluid Dynamics Code (EFDC) is a three-dimensional sigma coordinate hydrodynamic model coupled with a water quality model. The EFDC model has been used worldwide in environmental modeling of surface water hydrodynamics and transport. The EFDC model employs a vertical sigma-coordinate transformation to deal with irregular water depth. This coordinate transformation introduces additional terms in horizontal pressure gradients. It is well known that direct numerical discretization of the full sigma-transformation of the horizontal pressure gradient produces numerical errors when a steep bottom slope exists. Errors in pressure gradient calculations can cause errors in velocity field and ultimately can result in spurious transports. In this study, an effective numerical algorithm is presented to reduce numerical errors induced by the horizontal pressure gradient term in the sigma coordinate. The transformed pressure terms in the sigma coordinate are discretized in sigma grids into the similar finite difference form along z-levels as those in the z-coordinate. The corresponding values of buoyancy and density for pressure calculations are determined by the fourth order Lagrangian interpolation in the vertical direction in the sigma grids. The enhanced EFDC model code has been satisfactorily tested in three cases: (1) flat bottom basin, (2) coastal shelf, and (3) navigation channel. Results indicate that the conventional approach, dealing with horizontal pressure gradient terms in the original EFDC model, causes spurious surface elevation and errors in the velocity field. In comparison, use of a new algorithm in the enhanced EFDC model presented in this study significantly reduces numerical errors in predicting surface elevation and currents.
Direct Numerical Simulations (DNS) were conducted to study the shear instabilities in a one-layer model of coastal currents. The instabilities of the currents are affected by the wave-radiation damping, and depend on a convective Froude number, in a manner analogous to the known Mach-number effect in compressible flow. In addition to the energy loss due to the wave radiation, the shear instabilities are also affected by friction. In the limiting case of zero friction, the present DNS for the gravity-stratified flows of one layer are consistent with the LST (Linear Stability Theory) of Sandham and Reynolds (1991) for compressible flow. In the wave-less case, the DNS results agree with the LST of Chu, Wu and Khayat (1991) for open-channel flow. The general instabilities are correlated with two dimensionless parameters: convective Froude number and friction number. The convective Froude number, not the local Froude number, characterizes the wave radiation from the shear flows, while the friction number parameterizes the local energy dissipation. The wave-radiation damping and the frictional energy dissipation are mechanisms fundamental to the instabilities. Analogies are established from the DNS between open-channel flow and compressible flow, and between open-channel flow and gravity-stratified flow. The correlation of the instabilities with the Froude number and the friction number are valid for all currents admissible to waves.
The hydrodynamics of coastal zones are extremely complicated, being influenced greatly by shallow water waves and currents induced by wave breaking. This paper presents numerical simulations of long-shore currents induced by the breaking of oblique incident waves in shallow coastal zones. The wave numerical model is based on parabolic mild slope equation, and so the wave radiation stress required for the generation of wave-induced currents are calculated based on the variables in the parabolic mild slope equation, and the long-shore currents have been numerically simulated based on these. The numerical models are validated against experimental data, and the results suggest that the long-shore current velocity and wave set-up increase with the increasing incident wave amplitude and offshore slope steepness, as well as the wave set-up increase with the increasing incident wave period.
This paper describes the development, calibration and validation of a two-dimensional numerical model coupled waves and tidal currents. The model consists of two component models, namely, 2-D random wave model (RWM) including refraction-diffraction and 2-D depth-integrated shallow water model (DSWM). First of all, the random wave model (RWM), which the Wen's spectrum formulation is introduced, can simulate the random wave propagation with the unsteady-uneven tidal currents under the condition of a mild topography on a large scale. The energy losses of wave breaking and wave propagation against the tidal currents are also included. It is applied to two cases, the seabed of the semi-ellipsis slanting slope and the northern area of the Bohai Sea. Secondly, the 2-D depth-integrated shallow water model (DSWM) with waves uses an unstructured triangular grid, which fits topography and coastal line of complicated model domain, for the spatial integration of the water levels and velocities. An explicit numerical time stepping scheme is implemented. In model, the bottom shearing stress with interactions of wave and tide current, radiation stress and Coriolis force's influence are considered, thus implementing the waves and tidal currents coupling simulation. The horizontal eddy viscosity term is introduced so as to increase stability and accuracy. Because of the shallow depths in domain, the model deals with areas where flooding and drying occur. Finally, the model is applied to simulate the waves and tidal currents on the northern area of the Bohai Sea. Comparisons of modeled waves and tidal currents with measurements indicate good agreement and demonstrate the capability of the model as a forecasting tool.
In this paper, a computationally-efficient scheme is developed to assimilate radar images into a pseudo-spectral wave evolution model. The nonlinear wave model uses a fourth-order Runge-Kutta scheme to integrate in time a coupled set of equations for the evolution of the free surface elevation and velocity potential at the free surface. An asymptotic expansion of the model variables in terms of wave steepness parameter is used to close the system of equations and determine the vertical velocity at the free surface from the velocity potential at the free surface. A variational data assimilation scheme is then developed to find an optimal initial wave field that minimizes a cost function defined as the squared difference between model predictions and radar observations over an assimilation interval. The conjugate gradient method is used for the minimization scheme with the adjoint technique used to calculate the gradient of the cost function with respect to the initial condition. Numerical experiments have been conducted with one dimensional pseudo-observations that have been generated by the forward model by adding uncorrelated noise, as well as synthetic radar data to validate the proposed assimilation scheme.
Near-shore surface water waves and wave-induced currents are important hydrodynamic factors in coastal zones. Propagation of irregular water waves and irregular breaking-wave induced near-shore currents have been numerical studied based on parabolic mild slope equation and near-shore currents model. Based on the JOSNWAP wave spectrum, the parabolic mild slope equation incorporating irregular and wave-breaking effects have been applied to model water waves. The wave radiation stresses exerted on currents have been calculated based on variables in the parabolic mild slope equation, and near-shore wave-induced currents have been numerically simulated based on these. The numerical results have also been validated and analyzed. It is believed that the presented numerical models are capable of adaptation to numerical simulating wave-induced near-shore circulation.
This paper presents a method of integrating hydrodynamic modeling with frequency analysis to predict a 100-year storm surge in the coastal waters of Pensacola Bay, Florida. The ADCIRC hydrodynamic model was applied to Pensacola Bay, and was calibrated by using observations of water levels from the storm surge of Hurricane Ivan in 2004. The calibrated hydrodynamic model was used to predict extreme flood areas in Pensacola Bay, and was based on the frequency analysis of annual maximum water levels at the NOAA station in the Bay. The water levels of a 100-year return period at the NOAA station were obtained from frequency analysis, and further used to derive a synthetic storm-surge hydrograph at the ocean boundary. Under the gravity forcing as specified in 100-year boundary storm surge hydrograph, hydrodynamic modeling was conducted to predict spatial distributions of maximum water levels in the bay. The model prediction of a water level of 3.2 m at the NOAA station matches well with that from the frequency analysis of 100-year water elevation, and indicate that maximum water levels are affected by the wind.
From 1988 to 1998, silvicultural activities impacted 5,856 km of rivers and streams in the southern United States. Internal cycling of nutrients from the water column and sediment in a forest can be an important contribution to the nutrient load of aquatic ecosystems. Therefore, understanding nutrient transport in forests can aid efforts to protect aquatic resources. Two watersheds in Tate's Hell State Forest in northwest Florida were selected to conduct a study of silvicultural impacts on surface water quality. Of the two sites one had been impacted with ditching and fertilization while the other site was not. From June 2003 to May 2005 a field study determined nutrient [nitrate-nitrogen (NO3-N); ammonia-nitrogen (NH3-N) and ortho-phosphate (PO4−)] concentrations in run-off water and sediment in these watersheds. Results showed NO3-N, NH3-N and ortho-phosphate concentrations in water and sediment, were higher at the impacted site verses the non-impacted site. At the impacted site NO3-N, NH3-N and ortho-phosphate concentrations in the water column were 16% to 33%, 39% to 47% and 66% higher, respectively. Nutrient concentrations in sediment from the impacted site were significantly (p< 0.05) higher than those from the un-impacted site and ranged (in mg kg−1) from 0.25 ± 0.01 to 0.44 ± 0.03 for NO3-N; 6.41 ± 0.19 to 12.77 ± 0.45 for NH3-N; and 1.01± 0.02 to 1.50 ± 0.02 for PO4−. In this ecosystem sediment acted as a source of NH3-N and ortho-phosphate and as a sink for NO3-N. These results indicate that proper management of inactive silvicultural sites is necessary to mitigate nutrient transport to aquatic systems.
A Calibrated High-Resolution Precipitation Database (CHPD) represents an enhanced tool for modelers developing Total Maximum Daily Loads (TMDL) or using water resource related surface water (SW), ground water (GW) or integrated SW-GW models. With software support from the National Oceanic and Atmospheric Administration (NOAA), funding support by the Florida Department of Environmental Protection (FDEP) and the Environmental Protection Agency, and academic support from Florida State University (FSU), Florida is the first State to have successfully completed the construction of a practical CHPD. Precipitation input for a watershed model typically has relied on weather data obtained from rain gauges that are sparsely distributed in a watershed. A popular method for computing precipitation is the Thiessen method. This method assigns an area called a Thiessen polygon around each gauge. The polygon is an area in which every interior point is closer to the particular gauge than to any other. In effect, the precipitation in the entire polygon is assumed to be uniform and equal to the gauge value. This method does not provide information about the rainfall distribution between gauges. In addition, the method cannot give the true rainfall distribution for isolated or fast moving storms that may cover one side of a street, but not the other, and change intensity and coverage along its passage. Hourly Doppler radar-derived rainfall (NEXRAD/WSR-88) estimates possess superior temporal and spatial resolution compared to gauges and can be applied to watershed modeling as part of TMDL projects. The Doppler-derived precipitation estimates are produced hourly on a 4-kilometer by 4-kilometer grid covering the nation. This paper introduces the eleven years of historical precipitation data in CHPD released through FDEP's computer world-wide-web server and the CHPD applications by using three watershed models – WAMView, Mike-SHE, and WASH. The WAMView application assesses the potential benefits of CHPD data in the Black Creek Basin, which is a small (1,253 Km2) watershed in North Florida. The Mike-SHE application investigates the comparative diagnostic advantages of using fully distributed CHPD- or Thiessen (gauge)-derived rainfall rates in the Black Creek Basin of modest topography during both convective and synoptic conditions. The WASH application is the FDEP's first TMDL modeling project using the CHPD data.