Pauline Mollema, Marco Antonellini, Andrea Minchio, Giovanni Gabbianelli
description
Transcript of Pauline Mollema, Marco Antonellini, Andrea Minchio, Giovanni Gabbianelli
The Influence of 3D Dune The Influence of 3D Dune Topography on Salt Water Topography on Salt Water
Intrusion in Marina Romea, Italy: Intrusion in Marina Romea, Italy: a numerical modeling study using a numerical modeling study using
LIDAR DataLIDAR Data
Pauline Mollema, Pauline Mollema, Marco Antonellini, Marco Antonellini, Andrea Minchio, Giovanni GabbianelliAndrea Minchio, Giovanni Gabbianelli
Integrated Geoscience Research Group, University of Bologna, Italy
22 Mollema SWIM 2008Mollema SWIM 2008
Study AreaStudy AreaMarina Romea, Marina Romea, Province of Province of Ravenna, ItalyRavenna, Italy
Italy
River PoStudy area
PialassaPontazzo
Marina di Ravenna
Harbor
Marina RomeaFiume Lamone
Scolo Rivalone
Str
ada
stat
ale
309
Rom
ea
Lamone River
Pine Forest
N
2 km
PialasseSwamp
(salt)
Swamp(fresh)
Agriculture
N
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Study area 2Study area 2
Drain
River Lamone
Pine Forest
Beach, dunes and bathing establishments
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•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 Factors that may enhance salt water intrusion in unconfined aquifer Marina intrusion in unconfined aquifer Marina
RomeaRomea
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Monitoring of salinity and water table Monitoring of salinity and water table
River Lamone
Pine Forest
River Lamone
Drain
PZMR3A
PZMR3B
PZMR2B
PZMRPCPZMR4B
Dunes17g/l
18g/l
100 m
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Monthly Monitoring of Salinity in Monthly Monitoring of Salinity in PiezometersPiezometers
Dunes 2007-2008
0
10
20
30
March 07
Sal
inity
[g/
l]
Pine Forest 2007-2008
PZMR2B
0
10
20
30
Sal
inity
[g/
l]
PZMRPC
PZMR4B
PZMR3BPZMR3A
Feb 08
March 07 Feb 08
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Light Detection and Ranging (LIDAR)Light Detection and Ranging (LIDAR)
SUBSIDENCERavenna’s historical center subsided 70 cm between 1953-1995The coastal zone more than 1 mDue to water and gas extraction
RESULTNo accurate topographic maps
THEREFOREWe used LIDAR data to construct a topographic map
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River Lamone
Pin
e F
ore
st
LIDAR DATA in Triangulated Irregular LIDAR DATA in Triangulated Irregular Network (TIN) formatNetwork (TIN) format
Adriatic sea
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Sampling of LIDAR data in GRID of 10 *10 mSampling of LIDAR data in GRID of 10 *10 m
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River Lamone
Pin
e F
ore
st
Original Lidar data versus Gridded data Original Lidar data versus Gridded data
Original LIDAR data TIN of 10 by 10 m grid
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ModelModel
SEAWAT (USGS)SEAWAT (USGS)
Visual Modflow Interface (SWS Visual Modflow Interface (SWS Schlumberger Water Services)Schlumberger Water Services)
10 layers, 54 columns 36 rows10 layers, 54 columns 36 rows
Simulation period 60 years – 100 yearsSimulation period 60 years – 100 years
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Adriatic SeaGeneral Head Boundary
Kx=ky=Kz=0.00069 m/s SandKx=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 GeologyPine ForestRecharge 15 mm/yr
DunesRecharge 200 mm/yr
DrainConductance10m/day
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Model without drain, simulation time 60 Model without drain, simulation time 60 yearsyears
SeaDunes West
540 m
35g/l
<1 g/l
20 m
3m
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Model with drain simulation time 60 yearsModel with drain simulation time 60 years
SeaDrainDunesWest
540 m
T=60 anni
0.3 g/l
20 m
3m
35g/l
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Sea
DunesDrain
Map of water table contours Map of water table contours Layer 1 model with drain after 60 years.Layer 1 model with drain after 60 years.
0.2mLayer 1, sand
0.1m0.12 m
0.14 m
N
N
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Sea
DunesDrain
Map of water table contours Layer 4 model Map of water table contours Layer 4 model with drain after 60 years.with drain after 60 years.
0.0m.
0.1m0.1m0.2m
Layer 4, sand clay silt
N
N
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Sea
DunesDrain
N
Map of salt concentration contours Layers 1 Map of salt concentration contours Layers 1 and 4 model with drain.and 4 model with drain.
LAYER 1sand
LAYER 4LAYER 4Sand clay silt
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Model with drain simulation time 100 yearsModel with drain simulation time 100 yearsSea
Drain
West
540 m
T=60 anni0.3 g/l
20 m
3m
35g/l
20g/l
30g/l
20g/l10g/l
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Model with Drain and high dispersivity (10 Model with Drain and high dispersivity (10 m) and high vertical conductivitym) and high vertical conductivity
T= 60 years
SeaDrainWest
540 m
3g/l
HIgher salt concentrations under dunes, but not in rest of aquifer.
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Model with thin sand formation at top, high Model with thin sand formation at top, high dispersion (10m) and Kz=Kxdispersion (10m) and Kz=Kx
V
Kx=Ky=Kz=6.9E-4m/s
Kx=Ky=Kz=5.8-5m/s
Kx=Ky=Kz=1.2E-6m/s
SeaEW
540 m
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Model with thin sand formation at top, high Model with thin sand formation at top, high dispersion (10m) and Kz=Kxdispersion (10m) and Kz=Kx
10g/l
20g/l
0.05m0.05m
0.0m
drainSeaEW
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Map of head contours Layer 1 Map of head contours Layer 1 Model with drain, thin sand layer at topModel with drain, thin sand layer at top
0.07m0.07m
0.08m
TOPOGRAPHY
540 m
Sea
DunesDrain
NLayer 1 sandHead [m]
0.02
0.02
0.03
0.04
0.08
0.05
0.06
0.07
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Sea
DunesDrain
Map of salt concentration contours Layer 1 Map of salt concentration contours Layer 1 model with drain, thin sand layer at topmodel with drain, thin sand layer at top
15g/l10g/l10g/l
10g/l
25g/l
10g/l
Layer 1 sand
N
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ConclusionsConclusionsLidar data is useful to create topographic maps Lidar data is useful to create topographic maps Effect of dune topography on salt water intrusion in Effect of dune topography on salt water intrusion in Marina Romea is small, visible only in uppermost low Marina Romea is small, visible only in uppermost low conductivity layers, not in sand above.conductivity layers, not in sand above.Dune destruction cannot be sole cause of salinization of Dune destruction cannot be sole cause of salinization of unconfined aquifer: topography and recharge are large unconfined aquifer: topography and recharge are large enough to maintain a layer of fresh water.enough to maintain a layer of fresh water.Dune topography has a larger influence on water table Dune topography has a larger influence on water table and salt distribution if dispersivity is high, if interface and salt distribution if dispersivity is high, if interface sand-silt is close to surface and if Kz is high.sand-silt is close to surface and if Kz is high.Our model is insensitive to initial salt concentrationOur model is insensitive to initial salt concentrationThe salt concentrations are still responding to changes The salt concentrations are still responding to changes (dune destruction) started 60 years ago.(dune destruction) started 60 years ago.