1. The Influence of 3D Dune Topography on Salt Water Intrusion in Marina Romea, Italy: a numerical modeling study using LIDAR Data Pauline Mollema, Marco Antonellini, Andrea Minchio, Giovanni Gabbianelli Integrated Geoscience Research Group, University of Bologna, Italy

2. 2 Mollema SWIM 2008 Study Area Marina Romea, Province of Ravenna, Italy Italy River Po Study area Pialassa Pontazzo Marina di Ravenna Harbor Marina Romea Fiume Lamone Scolo Rivalone Strada statale 309 Romea Lamone River Pine Forest N 2 km Pialasse Swamp (salt) Swamp (fresh) Agriculture N

3. 3 Mollema SWIM 2008 Study area 2 Drain River Lamone Pine Forest Beach, dunes and bathing establishments

4. 4 Mollema SWIM 2008 Dune destruction Land drainage Subsidence Presence of salt water in river on north and swamp on west Beach erosion Evapotranspiration Pine Forest Connate water Factors that may enhance salt water intrusion in unconfined aquifer Marina Romea

5. 5 Mollema SWIM 2008 Monitoring of salinity and water table River Lamone Pine Forest River Lamone Drain PZMR3A PZMR3B PZMR2B PZMRPC PZMR4B Dunes 17g/l 18g/l 100 m

6. 6 Mollema SWIM 2008 Monthly Monitoring of Salinity in Piezometers Dunes 2007-2008 0 10 20 30 March 07 Salinity [g/l] Pine Forest 2007-2008 PZMR2B 0 10 20 30 Salinity [g/l] PZMRPC PZMR4B PZMR3B PZMR3A Feb 08 March 07Feb 08

7. 7 Mollema SWIM 2008 Light Detection and Ranging (LIDAR) SUBSIDENCE Ravenna’s historical center subsided 70 cm between 1953-1995 The coastal zone more than 1 m Due to water and gas extraction RESULT No accurate topographic maps THEREFORE We used LIDAR data to construct a topographic map

8. 8 Mollema SWIM 2008 River Lamone Pine Forest LIDAR DATA in Triangulated Irregular Network (TIN) format Adriatic sea

9. 9 Mollema SWIM 2008 Sampling of LIDAR data in GRID of 10 *10 m

10. 10 Mollema SWIM 2008 River Lamone Pine Forest Original Lidar data versus Gridded data Original LIDAR data TIN of 10 by 10 m grid

11. 11 Mollema SWIM 2008 Model SEAWAT (USGS) Visual Modflow Interface (SWS Schlumberger Water Services) 10 layers, 54 columns 36 rows Simulation period 60 years – 100 years

12. 12 Mollema SWIM 2008 Adriatic Sea General Head Boundary Kx=ky=Kz=0.00069 m/s Sand Kx=Ky=5.8E-6m/s Kz=1/3 Kx Sand Clay Silt Kz=1/3 Kx=Ky=3.5E-9 m/s Clay 360 m 540 m Constant Head Boundary 0.2 m Grid, Boundary Conditions and Geology Pine Forest Recharge 15 mm/yr Dunes Recharge 200 mm/yr Drain Conductance 10m/day

13. 13 Mollema SWIM 2008 Model without drain, simulation time 60 years Sea Dunes West 540 m 35g/l <1 g/l 20 m 3m

14. 14 Mollema SWIM 2008 Model with drain simulation time 60 years SeaDrain Dunes West 540 m T=60 anni 0.3 g/l 20 m 3m 35g/l

15. 15 Mollema SWIM 2008 Sea Dunes Drain Map of water table contours Layer 1 model with drain after 60 years. 0.2m Layer 1, sand 0.1m 0.12 m 0.14 m N N

16. 16 Mollema SWIM 2008 Sea Dunes Drain Map of water table contours Layer 4 model with drain after 60 years. 0.0m. 0.1m 0.2m Layer 4, sand clay silt N N

17. 17 Mollema SWIM 2008 Sea Dunes Drain N Map of salt concentration contours Layers 1 and 4 model with drain. LAYER 1 sand LAYER 4 Sand clay silt

18. 18 Mollema SWIM 2008 Model with drain simulation time 100 years Sea Drain West 540 m T=60 anni 0.3 g/l 20 m 3m 35g/l 20g/l 30g/l 20g/l 10g/l

19. 19 Mollema SWIM 2008 Model with Drain and high dispersivity (10 m) and high vertical conductivity T= 60 years Sea Drain West 540 m 3g/l HIgher salt concentrations under dunes, but not in rest of aquifer.

20. 20 Mollema SWIM 2008 Model with thin sand formation at top, high dispersion (10m) and Kz=Kx V Kx=Ky=Kz=6.9E -4 m/s Kx=Ky=Kz=5.8 -5 m/s Kx=Ky=Kz=1.2E -6 m/s Sea E W 540 m

21. 21 Mollema SWIM 2008 Model with thin sand formation at top, high dispersion (10m) and Kz=Kx 10g/l 20g/l 0.05m 0.0m drain Sea E W

22. 22 Mollema SWIM 2008 Map of head contours Layer 1 Model with drain, thin sand layer at top 0.07m 0.08m TOPOGRAPHY 540 m Sea Dunes Drain N Layer 1 sand Head [m] 0.02 0.03 0.04 0.08 0.05 0.06 0.07

23. 23 Mollema SWIM 2008 Sea Dunes Drain Map of salt concentration contours Layer 1 model with drain, thin sand layer at top 15g/l 10g/l 25g/l 10g/l Layer 1 sand N

24. 24 Mollema SWIM 2008 Conclusions Lidar data is useful to create topographic maps Effect of dune topography on salt water intrusion in Marina Romea is small, visible only in uppermost low conductivity layers, not in sand above. Dune destruction cannot be sole cause of salinization of unconfined aquifer: topography and recharge are large enough to maintain a layer of fresh water. Dune topography has a larger influence on water table and salt distribution if dispersivity is high, if interface sand-silt is close to surface and if Kz is high. Our model is insensitive to initial salt concentration The salt concentrations are still responding to changes (dune destruction) started 60 years ago.