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Indian River Lagoon

Numerical Model Flushing Experiments

(Draft)

Submitted to the

St. Johns River Water Management District 4049 Reid Street

Palatka, FL 32177

Gary A. Zarillo, Ph.D., PG Florida Institute of Technology

Melbourne, FL 321 794-3398 zarillo@fit.edu

April 27, 2015

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Executive Summary In order to examine the potential for improved flushing of the Indian River Lagoon (IRL)

U.S. Army Corps of Engineers Coastal Modeling System (CMS) was used for hydrodynamic and transport modeling. The CMS is an integrated 2D numerical modeling system for simulating circulation, water level, constituent transport, sand transport, and morphology change in shallow water environments. For this project, two computational model grids were constructed to cover the Indian River Lagoon System from the north end of the Mosquito Lagoon (ML) in Volusia County. FL to the Wabasso area of Indian River County. The north grid (Grid 1) includes the Mosquito Lagoon and the north compartment of the Indian River Lagoon (IRL) The south grid (Grid 2) includes the Banana River and the IRL from the Cocoa area to Wabasso. A uniform grid resolution of 50 was found to provide adequate spatial resolution and numerical stability. The model boundaries were forced with historical time series of water level and with discharge at major creeks and rivers entering the west bank of the IRL. Wind speed and direction were applied over the surface of the model grid.

A total of seven model runs were conducted, including two runs to simulate existing conditions. Model performance was validated by comparing predicted and measured water level time series. Five model runs included hypothetical new tidal inlets, pumping stations, and hypothetical widening of Sebastian inlet near the south boundary of Grid 2. Flushing rates were predicted by establishing an initial numerical tracer concentration of 20 parts per thousand over the entire model domain. Tracer concentrations at the model boundaries were then set to zero.

Model results for existing conditions were consistent with previous studies by showing that the southern portion of the Mosquito Lagoon and the Banana River remain poorly flushed over long periods of time. The Titusville area of the IRL also remained poorly flushed in model simulations of existing conditions. Among the hypothetical alterations to the model grids, additional tidal inlet and pumping station connections to the coastal ocean across narrow sections of the barrier island, produced the best flushing results in the model grids. Either a narrow tidal inlet or pumping station located in the south compartment of the Mosquito Lagoon produced complete flushing of the ML and north compartment of the IRL (Grid 1) within about 70 days or less. A tidal inlet across the South Cocoa Beach barrier island segment also substantially improved flushing of the Banana River. Opening the water locks at Port Canaveral also improved flushing, but at a somewhat slower rate to the tidal inlet case. This is attributed to the long conveyance channel between the Port entrance and the Banana River, which may dissipate tidal energy to a greater degree. Widening of Sebastian Inlet to twice its present width at the throat section did not noticeably improve flushing rates or extent

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Table of Contents

Executive Summary ........................................................................................................................ ii 

Introduction and Goals ................................................................................................................... 1 

Model Features ............................................................................................................................ 1 

Model Setup .................................................................................................................................... 2 

Grid Generation .......................................................................................................................... 2 

Wind Time Series ....................................................................................................................... 5 

Model Validation ............................................................................................................................ 5 

Model Runs ..................................................................................................................................... 7 

Model Results ................................................................................................................................. 8 

Model Run1 Predicted Flushing, North Grid .............................................................................. 8 

Model Run 2; Predicted Flushing, South Grid............................................................................ 9 

Model Run 3: Tidal Inlet, Mosquito Lagoon ............................................................................ 10 

Model Run 4: Pumping Station, Mosquito Lagoon .................................................................. 12 

Model Run 5: Tidal Inlet – South Cocoa Beach ....................................................................... 13 

Model Run 6: Canaveral Locks Open ....................................................................................... 14 

Model Run 7: Widening of Sebastian Inlet ............................................................................... 16 

Conclusions ................................................................................................................................... 17 

References ..................................................................................................................................... 18 

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Introduction and Goals

Preliminary model circulation experiments were performed in 2013 that involved structural modification of the Indian River Lagoon geometry. These included adding a small tidal, a pump station, and hypothetical widening of Sebastian Inlet. This exercise showed that some influence on tidal circulation and tidal amplitude would occur within the Indian River Lagoon compartment around Sebastian Inlet. This exercise applied the 2-dimensional coastal Modeling System (CMS) developed by the Coastal hydraulics Laboratory for use in shallow coastal areas.

In the present project, the earlier work is expanded to examine flushing rates in the north and central Indian River Lagoon compartments and the Mosquito Lagoon. Hypothetical inlets and pumping station canals were added to the IRL at selected locations, along with model tests involving widening of Sebastian Inlet and opening of the water locks within the interior of port Canaveral. Although CMS is capable of including wave propagation, sediment transport, and morphologic change over time, model tests were restricted to simulation of flushing times without considering potential consequences of modification of IRL geometry on processes like wave-driven littoral drift, shoal building, and regional sediments budgets.

The goal of applying numerical tests of flushing rates in the north and central IRL, is to identify the potential for improving the state of water qualify by promoting more rapid exchanges with the coastal ocean. Although the likely side effects of promoting exchanges in terms of morphodynamics are not considered in this project, model forcing was kept as real as possible by including real time series of water elevation and discharge inflows at model boundaries.

Model Features

The Coastal Modeling System (CMS) was developed by the U.S. Army Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL). CMS is a coupled group of numerical models for calculating waves, circulation, sediment transport, constituent transport, and morphology change. Calculations can be performed for flows generated by tide, wind, waves, river discharges, and changes in salinity. A significant study for model verification and validation of the CMS is documented in Demirbilek (2011), Lin (2011), Sanchez (2011a) and Sanchez (2011b). Further documentation of the CMS including processes and numerics are documented in Wu (2010) and Buttolph (2006).

CMS-Flow is a 2-D finite-volume model that solves the mass conservation and shallow-water momentum equations of water motion. CMS-Flow is forced by water surface elevation (e.g., from tide), wind and river discharge at the model boundaries, and wave radiation stress and wind field over the model computational domain.

CMS-Flow is presently capable of 2-D transport computations in both the explicit and implicit solvers. The simulation of constituent transport can often require a three-dimensional (3-D) solution due to the presence of vertical gradients that can influence the flow. It is therefore

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important to understand the limitations of 2-D transport simulations, and apply them only when the assumptions inherent in 2-D simulations are valid. Typically, 2-D salinity simulations are valid in a well mixed the water column. These conditions are usually met for shallow bays with open exchanges to the ocean or gulf, and strong tidal signals and sufficient wind energy to provide the vertical mixing. Thus it is assumed that the Indian River Loon system is largely well mixed in the vertical and over time scales of the computations performed in the study, which are the order of 1 year.

Model Setup Grid Generation

Two model grids were constructed, one covering the Mosquito lagoon and the north compartment of the Indian River Lagoon (IRL. The second grid included Indian River lagoon compartments between Titusville and the Wabasso area of north Indian River County, FL. Having two model grids facilitated shorter computational run times and more model tests running on several computers. Model grids resolution was set at 50 meters and both grids were generated in the AquaveoTM Surface Water Modeling System (SMS) Platform. Figure 1 illustrates the north grid and Figure 2 shows the south grid.

Figure 3 shows the available monitoring data assembles though the efforts of the St. Johns River Water Management District (SJRWMD). In general the monitoring time series covers the period between 1996 and 2006. Some data sets extend through 2006. The boundaries of the two model grids were set to correspond to available water level time series and in some cases discharge time series.

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Figure 1. Configuration of Model Grid 1 (north grid)

Figure 2. Configuration of Model Grid 2 (south grid)

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Boundary Water Level and Discharge Time series

For the existing condition model runs over the north grid (Figure 1) water level boundary conditions were set at the north end of the mosquito lagoon (mosquito) and at the Titusville bridge station (titubrew, Figure 3). The time period represented for the Grid 1 model run is 1999 since the station records included very few data gaps. Time series of water level and discharge from Turnbull Creek were not included since the data records from this station ended in March 1998. Discharges from the District HSPF watershed sub-basin model were not included since they are predicted, very small, and distributed over a large area. The selected model time period for Grid 2 (North IRL to Wabasso area) is 1997, which includes the most complete time series of data for boundary conditions. Discharge time series were applied at the Eau Gallie, River, Crane Creek, Turkey Creek, in the Sebastian River where the gauged discharges from the S-157 structure and the Fellsmere Canal were combined. Figure 4 shows model details around the Sebastian area including water level and discharge inputs at CMS boundary cell strings.

Figure 3. Location of monitoring stations throughout the north and central Indian River Logoon.

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Wind Time Series

CMS flow will assimilate wind data as multiple inputs over selected cells or as global input over the entire model domain. In this study three wind records were applied, The wind record (1999) applied to Grid 1 was taken from the Pone de Leon Inlet (poneinl , Figure 3) metrological station including globally for over Grid 1. Wind records applied to Grid 2 (1997) were taken from the Banana River and Ft. Pierce Inlet metrological stations (See Figure 3)

Figure 4. Model grid detials and boundary conditions in the Sebastian Inlet area

Model Validation Two data records were used to validate model predictions relative to water elevation. A

portion of the 1999 water level record from Haulover Canal (Station Haulover, Figure 3) was compared to predicted water levels at e same location. Figure 5 shows time series of measured and model data at the Haulover Canal station. The R-square value of 0.90 refers to a bivariate comparison of the data. Similar to calibration results for the hydrological and water quality mode

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of the Mosquito Lagoon (Zarillo et al, 2010) the best fit between measured and model data was found when the mean elevation north boundary water level time series was set down by 15 cm (-0.15m)

Figure 5. Model and measured water level comparison at Haulover Canal

Water level predictions on Grid 2 (south grid) were compared at station spsebars (see Figure 3) near the mouth of the Sebastian River. Figure 6 shows the comparison between measured and model data at this location. The R-square value of 0.90 refers to a bivariate comparison of the data. No adjustments were made to mean water level values at Sebastian Inlet or at the Wabasso Bridge water level time series to achieve the comparison shown in Figure 6.

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Figure 6. Model and measured water level comparison in the Sebastian River.

Model Runs

Table 1 lists model configuration for each of the model runs conducted in this study to evaluate flushing conditions. Each model run began with specifying an initial tracer concentration of 20 parts-per-thousand (ppt) throughout the model domain. Tracer concentration at the model boundaries was set to zero though each model run. The initial year-long runs were configured for existing conditions. Subsequent model configurations included hypothetical tidal inlets, a one- way pumping station, a widened version of Sebastian Inlet, and opening of the water locks to the west of Port of Canaveral entrance.

Table 1. Model Runs Model Run

Grid Configuration Duration

1 Grid 1 Existing 1999/365 days 2 Grid 2 Existing 1997/ 340 days 3 Grid 1 ML Inlet 1999/365 days 4 Grid 1 ML pumping station 1999/365 days 5 Grid 2 Inlet at PAFB 1997/ 340 days 6 Grid 2 Canaveral Locks Open 1997/ 340 days 7 Grid 2 Widen Sebastian Inlet 1997/ 340 days

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Model Results

The major model results of numerical flushing experiments are presented in an electronic appendix to this document for convenient review. The appendix includes a slide presentation that is linked animation files. A convenient video players is also included in the electronic appendix for convenient frame by frame viewing of the animation files that show tracer concentrations at a daily update time scale.

Model Run1 Predicted Flushing, North Grid

Results of model flushing experiments on Grid 1 (north grid) for the existing configuration are shown in Figures 7 and 8. The tracer concentration of 20 ppt decreased to less than half of the initial value over the north section of the grid within about 30 days. After 150 days of simulation the predicted tracer concentrations were less than 10 ppt over about 75% of the model domain (Figure 8A) At the end of the 365-day simulation tracer concentrations were near zero over about 80% of the Mosquito Lagoon and the north compartment of the IRL (Figure 8B). However the south end of the ML and north end of the IRL retained high tracer concentrations.

Figure 7. Predicted tracer concentration for Model Run 1, existing configuration at day 0 (A) and day 30 (B).

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Figure 8. Predicted tracer concentration for Model Run 1 existing configuration after 150 days (A) and 365 days (B)

Model Run 2; Predicted Flushing, South Grid

Figure 9 shows predicted tracer concentrations for the existing configuration of the IRL represented in model Grid 2. After about 150 days of simulation tracer concentrations remain above 50% percent of the initial value of 20 ppt over more than half the model domain. After 340 days of simulation tracer concentrations over most of the model domain are reduced but values remain well above 50% the initial 20 ppt over much of the area.

Figure 9. Predicted tracer concentration for the Model Run 2 existing configuration at day 0 (A), day 150, and day 340 (C).

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Model Run 3: Tidal Inlet, Mosquito Lagoon

Model Run 3 (Table 2) over Grid 1 included an inlet scale opening across the barrier island near the south end of Mosquito lagoon. Figure 10 shows the inlet configuration and water elevation time series paced in the 2 boundary cells representing the inlet. In order to preserve the calibration the same tidally influenced time series applied at the north boundary was applied without any further adjustments to the mean water elevation. The approximate width of the inlet is 50 meters. The refinement of 2 column of grids cells to accommodate the inlet width can be seen in Figure 10. Figure 11 shows the depth refinement associated with the inlet channel entering the IRL. The inlet throat as represented in the grid is 3 m deep and the conveyance channel extending west into the IRL is 2 to 2.5 m deep

Figure 10. Location of a hypothetical tidal inlet exchange with the Atlantic Ocean across the barrier island at south compartment of the Mosquito lagoon.

Results of the model run including the hypothetical inlet into the ML showed substantial decrease in the time to flush the entire ML and north compartment of the IRL. Figure 12 summarizes the results and shows about 50% of the system flushed to less than half the initial

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tracer concentration within about 30 days. After 70 days of simulation tracer concentrations are reduced to a few ppt or less over the system.

Figure 11. Details of the ML inlet channel receiving water level forcing from the coastal ocean.

Figure 12. Predicted tracer concentration for Model Run 3, ML tidal inlet after 30 days (A) and 70 days (B)

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Model Run 4: Pumping Station, Mosquito Lagoon

Model Run 3 applied a configuration similar to that of the ML inlet. However in this run the inlet configuration was converted to a pumping station in which a constant inflow of 100 m3/s was applied to a 50-m wide canal. The concept and dimension is similar to the engineered canal systems that provide coastal cooling water to power plants. The canal is represented by a grid column refinement 2-cells wide, each cell being about 25 m in width. An inflow of 50 m3/s was specified into the seaward side of the canal as shown in Figure 13

Figure 13. Pump intake canal located in the southern compartment of the Mosquito Lagoon.

Results of the pumping station model test are similar to those of the hypothetical tidal inlet at the same location. However the predicted rate of flushing is somewhat faster. After about 12 days of simulation half of the Mosquito lagoon is reduced to tracer concentrations below about 5 to 10 ppt (Figure 14A) After 30 days of simulation, the entire ML basin is at a tracer concentration of 10 ppt or less (Figure 14B After 50 days both the ML and north IRL compartments have low remaining tracer concentrations (Figure 14C).

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Figure 14. Predicted tracer concentration for Model Case 4, pumping station located in the south compartments of the ML (A, 12 days, B, 30 days and C, 50 days).

Model Run 5: Tidal Inlet – South Cocoa Beach

Model Run 5 on Grid 2 (see table 2) includes a hypothetical tidal Inlet cut through a narrow section of the barrier island immediately north of Patrick Air Force Base in South Cocoa Beach. Figure 15 shows the configuration of the inlet and input water level times series. The Sebastian Inlet water level time series was applied at the open inlet boundary without adjustment to the mean water level in order to maintain the model validation. Inlet dimensions.

Figure 15. Location of hypothetical tidal inlet located aross the barrie island at South Cocoa Beach (Model Run 5).

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Figure 16 summarizes the results of the Model Run 5 experiment. After 30 days of simulation, reductions in tracer concentration can be seen in the Sebastian Inlet area and in the and South Cocoa Beach area of the IRL. After 150 days of simulation the flushing influence of both inlets merge and extend into the Banana River compartment of the IRL. Completion of the model run at 340 days produces flushing effects to the north end of the Banana Rive. However, the north compartment of the IRL included in Grid 2 does not flush. Since no water level condition was specified at the north boundary of Grid 2 and the Canaveral barge canal extension ,was not included in the grid, the lack of flushing of this compartment just to the south of Titusville may not be realistic.

Figure 16. Predicted tracer concentration for Model Case 5, tidal inlet located at South Cocoa beach (A - 30 days, B – 90 days and C, 340 days).

Model Run 6: Canaveral Locks Open

Model Run 6 includes opening of the Port of Canaveral locks for free exchange with the Banana River as shown in Figure 17. Water Depths through the lock area were set at 3 to 5 m and the channel width set at about 50 m. Previous work by Zarillo et al, 2014 shows that the amplitude and phase of the tide at Sebastian Inlet is similar to that recorded at the Trident Pier NOAA water level gauge. Therefore, to be consistent with the overall modeling effort and to preserve the validation of the model, the measured water level time series was applied to the entrance of Port Canaveral (Figure 17).

Figure 18 summarizes the results of hypothetical opening the Canaveral locks on flushing of the IRL and Banana River. Predicted Tracer concentrations are shown at 30, 90 and 100 days of simulations for comparison to the tidal inlet case shown in Figure 16. Hypothetical opening of the Caravel locks results in flushing patens similar to that resulting from the south Cocoa beach tidal inlet. However, the rate of flushing is slower by comparison and the final result after 340 days of simulation, leaves higher tracer concentrations at the north end of the Banana River. The slower pace of flushing in the Canaveral Lock case is most likely due to the longer

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conveyance channel across Cape Canaveral compared to the length of the inlet across the barrier island at South Cocoa Beach.

Figure 17. Configuration of Model Run 7, hypothetical opening of the Port of Canaveral water locks

Figure 18. Predicted tracer concentration for Model Case 5, Canaveral locks open (A - 30 days, B – 90 days and C, 340 days).

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Model Run 7: Widening of Sebastian Inlet

Figure 19 shows the configuration of hypothetical widening of Sebastian Inlet. In this case the width of the inlet throat section is increased from about 150 m to about 300 meters. The inlet channel depth is similar to the existing case and ranges from about 3 to 6 m. No major changes to the interior of the inlet were made to the configuration of the dredged channel connecting the inlet system to the Intracoastal Waterway to the west.

Figure 19. Configuration of Model Run 7, hypothetical widening of Sebastian Inlet

Figure 20. Predicted tracer concentration for the Model Run 7, wider Sebastian Inlet at day 0 (A), day 150, and day 340 (C).

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Flushing rates and patterns predicted for hypothetical widening of Sebastian Inlet are similar to those predicted for the existing inlet configuration (Figures 9 and 20). After about 150 days of simulation tracer concentrations remain above 50% percent of the initial value of 20 ppt over more than half the model domain. More reductions in tracer concentration occur after 340 days of simulation, but similar to the existing case (Model Run 2) tracer values remain well above 50% the initial 20 ppt over much of the area.

Conclusions

Computed flushing results for existing conditions were similar previous studies, showing that that the southern portion of the Mosquito Lagoon and the Banana River are poorly flushed at time scales of several months or more. The Titusville area of the IRL also remained poorly flushed in model simulations of existing conditions.

The most improved flushing rates and extent resulted from adding either a tidal inlet inlet or pumping station connection to the coastal ocean across narrow sections of the barrier island. A narrow tidal inlet or pumping station located in the south compartment of the Mosquito Lagoon produced complete flushing of the lagoon and north compartment of the IRL (Grid 1) within 70 days or less. A tidal inlet across the South Cocoa Beach barrier island also substantially improved flushing of the Banana River included in Grid 2. Opening the water locks at Port Canaveral also improved flushing but at a somewhat slower rate. This is attributed to the long conveyance channel between the Port entrance and the Banana River, which may dissipate tidal energy to a greater degree than a shorter inlet connection. Widening of Sebastian Inlet to about twice the width at the throat section did not noticeable improve either the rate or extent of flushing in the IRL

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References

Buttolph. A.M., Reed, C.W., Kraus, N.C., Ono, N., Larson, M., Camenen, B., Hanson, H., Wamsley, T., and Zundel, A.K. 2006. Two-dimensional depth-averaged circulation model CMS-M2D: Version 3, Report 2, Sediment transport and morphology change. ERDC/CHL TR-06-09, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.

Demirbilek, Z., and Rosati, J.D. (2011). "Verification and Validation of the Coastal Modeling System, Report 1: Executive Summary," ERDC/CHL-TR-11-10, US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Vicksburg, Mississippi.

Lin, L., Demirbilek, Z., Thomas, R., and Rosati III, J. (2011). "Verification and Validation of the Coastal Modeling System, Report 2: CMS-Wave," ERDC/CHL-TR-11-10, US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Vicksburg, Mississippi.

Sanchez, A., Beck, T., Lin, L., Demirbilek, Z., Brown, M., and Li, H. (2012) CMS User Manual (DRAFT) ERDC/CHL, US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Vicksburg, Mississippi.

Sanchez, A., Wu, W., Beck, T.M., Li, H., Rosati III, J., Thomas, R., Rosati, J.D., Demirbilek, Z., Brown, M., and Reed, C. (2011a). "Verification and Validation of the Coastal Modeling System, Report 3: Hydrodynamics," ERDC/CHL-TR-11-10, US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Vicksburg, Mississippi.

Sanchez, A., Wu, W., Beck, T.M., Li, H., Rosati, J.D., Demirbilek, Z., and Brown, M. (2011b). "Verification and Validation of the Coastal Modeling System, Report 4: Sediment Transport and Morphology Change," ERDC/CHL-TR-11-10, US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Vicksburg, Mississippi.

Wu, W., A. Sanchez, and M. Zhang. 2010. An Implicit 2-D Depth-Averaged Finite-Volume Model of Flow and Sediment Transport in Coastal Waters. June 30 – July 5, 2010, 32ndInternational Conference on Coastal Engineering (ICCE 2010) Shanghai, China.

Zarillo, G., T.V. Belanger, K. Zarillo, J. Rosario-Lantin and D. McGinnis. 2011. The Development of a Hydrologic Model for Mosquito lagoon in Canaveral National Seashore. Natural Resources Report to the National Park Service. Contract No. N5180070017.