1. Influence of Groundwater flows on Wetland Restoration Project at Juniper Bay Swamy Pati Bio. & Ag. Engineering Dept., NCSU SSC 570 - Wetland Soils Term Paper Presentation

2. Outline Introduction Carolina Bays Wetland Restoration Requirements Project Objectives Methodology

3. Introduction Research project – Assessment of Groundwater flows at Juniper Bay and their impacts on the surrounding area. This project is a supplement to the wetland restoration project underway at Juniper Bay. Project mainly focuses on the influence of the subsurface flows on wetland restoration. Juniper Bay is one of the Carolina Bays, which are spread throughout the Southeastern Coastal plain of US.

4. Literature review – Origin of Carolina Bays Carolina Bays are small orientated depressions, elliptical to ovate in shape, that the south-eastern coastal plain of the united states in incredible density and range. Extend from the Delmarva Peninsula in north to the Okefenokee swamp in Northern Florida.

5. Arial Photograph

6. Origin of Carolina Bays D.W. Johnson, 1936 – shape and orientation, as well as presence of sandy rims are attributed to wind and wave action and depressions are attributed to the artesian process. W.F. Prouty, 1952 – comet or asteroidal body entering the earth atmosphere at an oblique angle from a relatively northwesterly direction. Bruce G. Thom, 1970 – Humate allows for a perched water table near the surface that would eventually evolve into shallow, wet depressions, orientated later by wind and wave action.

7. Origin of Carolina Bays J. Ronald Eyton & Judith I. Parkhurst, 1975 – considered the theory stated by Prouty, 1952 and then they stated finally that comets are the cause for the creation of Carolina Bays. Raymond T. Kaczorowski, 1977 – ruled out the extraterrestrial theory as a cause for Bay formation and supported Thom’s water table perching theory. He suggested that the only requirement for Bay existence is poor drainage leading to ponding mechanisms. Reference: http://bss.sfsu.edu/jdavis/geog810/1999/black.html

8. Hydrology of Carolina Bays The hydrology of Carolina Bays is influenced by subsurface flows inputs and fine textured soil or parent material layers that restrict the downward movement of stored water in the Bay. Studies on the complex hydrology of Carolina Bays have shown complex subsurface interaction with the surrounding area Local depressional hydrology superimposed on the regional subsurface hydraulic gradients of the landscape in which the bay occurred.

9. Wetland restoration Requirements Wetland restoration projects needs assessment of the site in all factors to meet the restoration goals set by the US Army Corps of Engineers. Wetlands hydrology, hydric soils, and plant community similar to the reference ecosystem be restored. Site assessment, identification of potential functions, methodologies to restore wetland functions, and effective assessment of progress of functional restoration.

10. Hydrologic aspects of Wetland Restoration Ditching and pumping in the surrounding area of the site Regional subsurface hydraulic gradients Filling the ditches is not suffice Regional hydrology must be assessed and restoration methods must account for restoration of historical regional surface and subsurface hydraulic gradients.

11. Juniper Bay

12. Groundwater flows at Juniper Bay Lateral Groundwater Flows Preliminary work suggests non-negligible gradients across JB boundary Core data suggest an effective bottom to the surficial system – Black Creek Confining Unit Current well/piezometer network insufficient to assess lateral flows

13. Stratigraphy

14. Importance of Perimeter Ditch Lateral boundary of the project is the perimeter ditch. It influences the flows in the surficial aquifer and prevents the flows between interior and exterior of the bay. It can effectively drain 100 feet to either side. Influence of the perimeter ditch through the partially confined sand layers underlying the surficial aquifer is one of the main trusts of the project.

15. Objectives Characterize the subsurface flows at four locations on the perimeter Interaction of the perimeter ditch Model the subsurface flows Develop the management recommendations.

16. Characterize the subsurface flows Four locations are selected around the perimeter of the project site. Coring work was started in these locations. Coring is being done at 5 points at each transect. These are the same points at which nests of piezometers will be installed.

17. North-facing view of the Juniper Bay

18. Locations of Piezometer Transects

19. Transect of Piezometer Nests

20. NW - Transect

21. SE - Transect

22. SW - Transect

23. NE - Transect

24. Characterize the subsurface flows With the cores collected at different locations saturated hydraulic conductivity tests are conducted and values are estimated. Then flows crossing site boundaries will be calculated.

25. Ksat table

26. Piezometers Piezometers are installed at these locations at all significant sand layer at each point on the transect. Hydraulic heads will be monitored in the piezometers and perimeter ditch. Instrumentation is installed with all the piezometers to monitoring the water levels. Hydraulic gradients, Hydraulic conductivities, lateral and vertical fluxes will be estimated

27. Future Work - Additional Field Work Perimeter cores (8-12) for stratigraphic data Ground-penetrating radar surveys

28. Additional Coring

29. Role of the Perimeter Ditch How deeply does the perimeter ditch influence subsurface flows? Could/should it be preserved to control boundary flows? What management scheme? Elimination of the perimeter ditch could increase wetland area by 30-100 acres.

30. Groundwater Modeling There are various different kinds of modeling software available to model groundwater. Some of them are CFEST, MIGRATE, DYNFLOW, MODFLOW, etc. Except MODFLOW most of the other groundwater flow models are used to simulate the solute or chemical transport phenomena. In this project we are mainly dealing with the hydraulic aspects of the groundwater flow, MODFLOW will be appropriate to use.

31. MODFLOW Input parameters: Aquifer parameters, hydraulic parameters, dimensionality, initial conditions boundary conditions. Some of the input parameters will be estimated from the field data.

32. MODFLOW MODFLOW simulates hydraulic head and velocity field distribution and they solve the groundwater flow equation. This model can handle multiple layer porous media, with either confined, unconfined or semiconfined. Heterogeneous, anisotropic or compressible porous media can also be modelled. Finite difference solution technique is used in this model.

33. MODFLOW

34. Number of layers and the input parameters change depending on the scenario the model is run for.

35. Modeling Using the model we predict the flows in the surficial aquifer for the entire site Model will be run for different management scenarios – w/ & w/o the perimeter ditch Predict the impacts of the conversion on the water table levels in adjacent properties

36. THANK YOU Questions?