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


Study area 2Study area 2

Drain

River Lamone

Pine Forest

Beach, dunes and bathing establishments


•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


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


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


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


River Lamone

Pin

e F

ore

st

LIDAR DATA in Triangulated Irregular LIDAR DATA in Triangulated Irregular Network (TIN) formatNetwork (TIN) format

Adriatic sea


Sampling of LIDAR data in GRID of 10 *10 mSampling of LIDAR data in GRID of 10 *10 m


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


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


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


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


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


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


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


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


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


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.


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


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


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


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


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.

pauline mollema, marco antonellini, andrea minchio, giovanni gabbianelli

Documents

sand layer

salt water intrusion

drain simulation time

sand formation

sand clay siltmodel

moriginal lidar data

kx sand clay siltkz

sandconclusionslidar