F. Carisi, A. Domeneghetti, A. Castellarin

Transcription

F. Carisi, A. Domeneghetti, A. Castellarin - DICAM, University of Bologna, Italy ([email protected])
ANTHROPOGENIC
IMPACTS ON THE
TERRITORY
CLIMATE
CHANGE
HYDROLOGICAL
PROCESSES
EVOLUTION
• Flood-risk evolution
• Increasing of potential damages during extreme flood events
Human-induced land-subsidence due to the pumping of underground
fluids in densely populated areas in the last half of the XX century
Japan
(Daito and Galloway, 2015)
Thailand
(Phien-wej et al., 2005)
Mexico
(Toscana and Campos, 2010)
Bangladesh
(Brown and Nicholls, 2015; Howladar and Hasan, 2014)
•
Rich literature on the effects of land-subsidence in coastal areas (salt-water intrusion,
decrease of the coastal floods return period)
•
Poor literature on the dynamics of hydraulic risk in rivers flood-prone areas
AIM OF THE STUDY:
if and how much the human-induced land-subsidence can change
the riverine potential flooding
•
•
•
•
•
High population density
Complex network of road
infrastructures
Montone River + natural streams
with artificial embankment
systems
higher damages
in case of extreme events or levee
failure
Land-subsidence rate: naturally in the
order of a few mm/year
Sudden land-subsidence acceleration
after World War II due to an intense
water and gas extraction from
underground (Gambolati et al., 1991;
Carminati et al., 2002)
•
> 1,5 m over an area of 10 km2
between the historical center and the
coastline (Teatini et al., 2005)
Current topography:
5m Digital Elevation Model (DEM)
Land-subsidence curves;
Land-subsidence 5m DEM
Back-warped DEM:
5m historical DEM describing ground elevations in 1897
Modification of the major discontinuities
elevation according to the real topography:
• + 1 m for the main railways
• - 1.5 m for the greater channels
•
•
•
•
Scenario “Curr”: current morphology without infrastructures
Scenario “Curr_Infr”: current morphology with main infrastructures
Scenario “Past”: 1897 reconstructed morphology without infrastructures
Scenario “Past_Infr”: 1897 reconstructed morphology with main infrastructures
Fully-2D hydrodynamic model TELEMAC-2D:
•
•
Non-structured computational mesh of triangular
elements
Accurate reproduction of the real flooding
dynamics, considering the main topographic
discontinuities
Input function:
•
•
Time [s]
Single breach in the left
embankment of the Montone River
Overflowing discharge calculated
by referring to a quasi-2D model
of the Montone-Ronco River
system
Maximum water depth (h) for all time
steps and for each scenario
(“Curr”, “Curr_Infr”, “Past”, “Past_Infr”)
Significantly flooded areas in
different scenarios
(water depths h ≥ 10 cm)
Scenario “Curr” vs “Past”
•
•
Present scenario: urban area is
mainly affected by flood-risk
1897: rural areas in the Eastern side
are mostly impacted by inundation
FAI (Flood Area Index, see Falter et al., 2012) quantifies the agreement between flooded
areas in different scenarios
𝑭𝑭𝑭𝑭𝑭𝑭 =
𝑨𝑨
𝑨𝑨 + 𝑩𝑩 + 𝑪𝑪
A = extent of the areas simulated as flooded in both scenarios
B = extent of the area that results flooded only in Scenario 1
C = opposite of B, i.e. areas flooded only in Scenario 2
THE CLOSER TO ONE THE FAI COEFFICIENT,
THE HIGHER THE SIMILARITY BETWEEN THE FLOODED AREAS ACCORDING
TO THE TWO SCENARIOS
Influence of land-subsidence
without infrastructures:
FAI = 0.74
Scenario A
“Curr_Infr”
“Past_Infr”
(CM) vs Cvs
(PM)
FAI = 0.74
Scenario “Curr_Infr” vs
“Past_Infr”
with infrastructures:
FAI = 0.83
B
(CM_I)
(PM_I)
Scenario A
“Curr”
vsvs
“Curr_Infr”
(CM)
CD
(PM)
FAI = 0.74
Scenario “Curr_Infr” vs
“Past_Infr”
with infrastructures:
FAI = 0.83
Scenario “Curr” vs “Curr_Infr”
Influence of the main
infrastructure on the current
topography:
• No significant alterations to flood
dynamics caused by land-subsidence
•
FAI = 0.52
Higher impact on flood-hazard caused by the construction
of canals and road and railways embankments
1
Scenario
2
Scenario
2 – Scenario
1
The flatter the lines around Δh=0,
the higher the similarity of the two
compared scenarios
Non-significant Δh
(lower than ±10 cm)
F = exceedance
probability of a
certain Δh
Reference scenario: Scenario “Curr_Infr”
(situation closer to reality: current DEM and schematization of major infrastructures).
Scenario “Curr_Infr”-“Past_Infr”
Scenario “Curr_Infr”-“Curr”
Scenario “Curr_Infr”-“Past”
Effect of land-subsidence only - Significant Δh: 11%
Effect of infrastructures only - Significant Δh: 61%
Effect of land-subsidence and infrastructures Significant Δh: 82%
• Land-subsidence: high
similarity between h in 1897’s
and in the current DEM
•
•
Most different scenarios:
“Curr_Infr” and “Past”
Very similar F values between
Scenarios “Curr_Infr”-”Past” and
Scenarios “Curr_Infr”-”Curr”
Effects of anthropogenic land-subsidence on river flood hazard:
•
Negative consequences on urban area mainly in current morphological
configuration
•
Rural areas in the Eastern side mostly impacted by inundation in 1897
•
Large and rapid differential ground lowering does not seem to lead significant
alterations to the flooding hazard
Comparison between the effect of land-subsidence and the influence of major
discontinuities:
•
Main infrastructures have a higher impact on flood hazard than the anthropogenic
ground lowering

F. Carisi, A. Domeneghetti, A. Castellarin

Transcription

Similar documents