Lower Cape Fear River Estuary Model Progress Report Jim Bowen, UNC Charlotte October 11, 2007 Charlotte, NC (via Centra)

Description of Model Application Open Boundary Elevation Cond. Lower Cape Fear River Estuary Schematic Black River, FlowBoundary Cond. Cape Fear R. Flow Boundary Cond. NE Cape Fear Flow Boundary Cond.

DO Conceptual Model BOD Sources Sediment Sediment O 2 Demand Cape Fear BOD Load NECF & Black R. BOD Load Muni & Ind. BOD Load decaying phytopl.

DO Conceptual Model BOD Sources, DO Sources Sediment Sediment O 2 Demand Ocean Inflows Surface Reaeration Phytoplank. Productivity MCFR Inflows

BOD Consumption DO Conceptual Model BOD Sources, DO Sources & Sinks Sediment Sediment O 2 Demand Ocean Inflows Surface Reaeration Input of NECF & Black R. Low DO Water

BOD Consumption DO Conceptual Model BOD Sources, DO Sources & Sinks Sediment Sediment O 2 Demand Cape Fear BOD Load NECF & Black R. BOD Load Ocean Inflows Surface Reaeration Input of NECF & Black R. Low DO Water Phytoplank. Productivity Muni & Ind. BOD Load decaying phytopl. MCFR Inflows

Modeling Developments 1.Finished Defining Model Grid Bottom roughness investigation Finished sizing marsh cells 2.Further Developed Salinity Boundary Condition at Estuary Mouth 3.Finished Hydrodynamic Model Calibration 4.WQ Predictions Using New Grid

Hydrodynamic Calibration - Summary, 8/07 Excellent agreement w/ temperature and salinity Elevation agreement (not shown) still needs some work to get predicted tidal amplitude attenuation to match observed attenuation

Model Grid Definition, Procedure Objective was to match tidal amplitudes at USGS Stations –Upper Estuary ( Lock and Dam 1, Black at Currie, NECF at Burgaw) –Middle Estuary (Navassa, NECF at Wilmington) –Lower Estuary (Marker 12)

Sizing Marsh Cells, Procedure Systematically varied grid parameters to match observed elevation data –Rougher bottoms damp tidal amplitudes –More off-channel storage in wetland cells damps tidal amplitudes

Step 1. Can changes in channel roughness produce desired amplitude attenuation? Used existing model grid

Existing Model Grid w/ changes described in August update 1004 water cells Has “marsh cells” in Black and NECF Marsh cells 2.0 m deep All cells have the same roughness See kmz file for more detail

Step 1. Can changes in channel roughness produce desired amplitude attenuation? Used existing model grid Varied roughness across grid –Typical value = 0.02 –Minimum = m (very smooth) –Maximum = m (very rough) Looked at changes in amplitude as bottom roughness increased

Results, Variable Bottom Roughness

Upper Estuary Stations Underdamped

Results, Variable Bottom Roughness Middle Estuary Stations Underdamped

Results, Variable Bottom Roughness Very little sensitivity to bottom roughness

Sizing Off-Channel Storage, Procedure 1.Went through model grid and resized “marsh cells” to roughly fit wetland delineations 2.Developed a method to quickly vary width and roughness of marsh cells, create EFDC grid files, and see results w/ Google Earth 3.Ran model many times w/ various marsh configurations and observed results

First step, try various marsh cell widths Varied marsh cell widths –Base case –Base case * 2 –Base case * 5 –Base case * 10 Determined how width changes affected tidal amplitudes

Base Case

Base Case, Width x 2

Base Case, Width x 5

Base Case, Width x 10

Results, Marsh Width Variation

Width ratio = 2.0 gives best results overall Need additional damping at Navassa Added additional marsh cells in middle estuary (V1, V2) Also tried smaller changes in marsh width (1.5, 2.0)

Version 1, Width x 2

Version 2, Width x 1.0/2.0

Version 3, Width x 1.5

Results, Tidal Amplitudes

Unable to match exactly the observed pattern in amplitude reduction V2, Width ratio = 2.0 (in green) determined to give the best results overall

Version 1, Width x 2

Previous Model Grid

New Grid Characteristics Off-channel storage locations based on wetland delineations 46 additional marsh cells added (1050 total cells) Additional off-channel storage added to each basin (Cape Fear, Black, NECF) Significant amount of marsh area added to middle and lower estuary

Results for New Grid Also investigated alternate boundary condition specification –Now use AM and PM max salinity at station M12 rather than daily max Now use hourly rather than 12-hour averaged monitoring data Looked at observed vs. predicted temperatures, salinities, elevations Compared results to those obtained previously w/ previous model grid

Elevations, Currie, June 04

Elevations, Burgaw, June 04

Elevations, Navassa, June 04

Elevations, NECF Wilm., June 04

Elevations, Mrkr 12, June 04

April - November 2004 Temp., 8/07

April - November 2004 Temp., New

April - November 2004 Temp., 8/07 Statistical Measures of Fit (units of deg C) mean(pred-obs) = ME_norm = RMSE = MAE = MAE_norm = RMSE_norm = r_squared = num data comparisons = 4150 r 2 adjusted for bias =

April - November 2004 Temp., New Statistical Measures of Fit (units of deg C) mean(pred-obs) = ME_norm = RMSE = MAE = MAE_norm = RMSE_norm = r_squared = num data comparisons = mse/var(obs) =

April - November 2004 Salinity, 8/07

April - November 2004 Salinity, New

April - November 2004 Salinity, 8/07

April - November 2004 Salinity, New

April - November 2004 Salinity, 8/07

April - November 2004 Salinity, New

April - November 2004 Salinity, 8/07

April - November 2004 Salinity, New

April - November 2004 Salinity, 8/07 Statistical Measures of Fit (units of PSU) mean(pred-obs) = ME_norm = RMSE = MAE = MAE_norm = RMSE_norm = r_squared = num data comparisons = mse/var(obs) =

April - November 2004 Salinity, 8/07 Statistical Measures of Fit (units of PSU) mean(pred-obs) = ME_norm = RMSE =2.64 MAE = MAE_norm = RMSE_norm = r_squared = num data comparisons = mse/var(obs) =

Summary of Progress Model grid now includes a significant amount of off-channel storage Salinity mean errors now very low (important for predicting dilution) Tidal elevation attenuation now well simulated Hydrodynamic & conservative transport submodels now calibrated

Summary of Progress, cont’d Also have developed a program for animating horizontal contour in Google Earth (good for showing DO results) Benoit Duclaud finished Masters thesis on new method for predicting reaeration (thesis, paper available next month)

Information Available Online See LCFR website for more info This presentation is available Google Earth files available for download –Grid and wetland data from presentation –Monitoring stations, point sources –Final EFDC grid information –NOAA bathymetry

Present Work Running water quality model now w/ new grid Still waiting to get BOD data from LCFR Program Finish assigning decay rates and redefining loads once additional BOD data are available Work on incorporating SOD data in a more detailed way Do additional model/data comparisons w/ DWQ special study data