Post on 09-Jun-2020
1
Floodproofing techniques for risk mitigation in urban areas
CWS Seminar Series 2018/2019Exeter, 13th May 2019
Prof. Giuseppe T AronicaDepartment of Engineering, University of Messina, ITALY
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Outlines
The new policy of flood risk management is to give more attention to
non-structural measures, allowing people to “living with floods” rather
than “fight against floods”.
Floodproofing can be defined as combination of structural and non-
structural changes, or adjustments made in the building that reduces or
prevents flood damage to the structure and/or its contents.
The talk will presents and discuss the most common flood proofing
techniques for urban flooding risk mitigation
Presentation will also deal with a practical application of these measures
by showing the results for a case study in the city of Barcellona, Sicily,
Italy which suffered a severe inundation in November 2011.
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Messina, 16 June 2018
Urban flooding
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Catania, 9 September 2015
Urban flooding
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.5
UK, various locations
Urban flooding
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Urban flooding events in urban areas more frequent than floods in natural areas even in case of correct drainage network dimensioning.
Further, very often these flooding involve small portions of urban areas (“patchy flooding”)
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0
0.05
0.1
0.2
0.4
0.6
0.8
1
T = 20 years
Probability
1
Genoa
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R H V E
The variables of risk equation
€T
h h
Dam
age
%
Fighting against the floods Living with the floods
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.9 Risk mitigation
Highlights in urban flood risk
Patchy flooding
Difficulties in implementing large flood defense systems(high costs, environmental impacts)
High frequency and fast events
Rapid implementation mitigation measures
Increasing resilience
Tailored to protecting sensitive buildings (i.e., hospitals..)
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Floodproofing
Floodproofing is defined as combination of
structural and non-structural changes, or
adjustments made in the building that reduces or
prevents flood damage to the structure and/or
its contents. It can also be stated as any
structural or non-structural measures intended
to prevent damage from flooding to a building.
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.11
USACE publications, 1995
http://www.publications.usace.army.mil/
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https://www.fema.gov/media-library-data/9a50c534fc5895799321dcdd4b6083e7/P-936_8-20-13_508r.pdf
FEMA (Federal Emergency Management Agency, 2013)
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.13 Floodproofing
Surface Water Management Plan, Environmental Agency, UK 2009
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Floodproofing
Wet proofing Dry proofing
• Raise the buildings
• Use of water-resistantmaterials
• Elevate the electricalcomponents and the inventory
• Valves for against backwater efects
• Sealing openings and walls (SEALING)
• Use of flood barriers, installed at the entrance of the buildings (SHIELDING)
• Flood barriers along riverbanks or crossing a street (SHIELDING)
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Flood proofing
Elevate the electrical components and the inventory
WET FLOOD PROOFING
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Floodproofing
DRY FLOOD PROOFING
Sealing openings and walls (SEALING)
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Flood proofing
DRY FLOOD PROOFING
Use of flood barriers, installed at the entrance of the
buildings (SHIELDING)
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Flood proofing
DRY FLOOD PROOFING
Use of flood barriers, installed at the entrance of the
buildings (SHIELDING)
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Flood proofing
DRY FLOOD PROOFING
Use of flood barriers, installed at the entrance of the
buildings (SHIELDING)
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Sealing openings and walls & closing openings (SEALING+ SHIELDING)
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Flood proofing
DRY FLOOD PROOFING
Flood barriers along riverbanks or crossing a street (SHIELDING)
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Flood proofingDRY FLOOD PROOFING
Flood barriers along riverbanks or crossing a street (SHIELDING)
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A real case application
Flood barriers are easier and quicker to install and are easier to remove. These flood protection ought to have an acceptable stability against
overturning and sliding
With excellent results, these barriers are commonly used in many parts of the world, especially in North Europe because there are typically
affected by clear water floods and therefore they can easily withstand the hydrodynamic forces
In some situations, like Mediterranean areas, water floods are full of sediments and flows very fast.
Is stil possible to use “normal” flood barriers to reduce and mitigate risk?
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.24 Case study
Area (km 2 ) 1,297
Main branch (km) 2,6
Mean elevation (m) 318
Max elevation (m) 581
Min elevation (m) 54
Area (km2) 32
Main branch (km) 13.4
Mean elev. (m) 400
Max elev. (m) 1162
Mean slope (m) 0.18
LONGANO CATCHMENT
Barcellona
Barcellona, 22 November 2011
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.25 Case study
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Cu
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time on 22/11/2011
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10
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(m
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time on 22/11/2011
Rainfall
Discharge
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Barcellona, 22 November 2011
Case study
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Choose of the location for the flood barriers
Simulations with a hydrodynamic
model (MLFP-2D)
Hydrodynamicverification
Final choice of flood barriers
Case study
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S.P.
CASELLO
6050
5045
5046
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23.9
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27.4
28.4
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32.7
34.0
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15.7
15.4
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7.9
7.3
14.1
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28.4
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27.8
15.6
13.3
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16.8
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41.4 45.8
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38.6
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48.3
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105.8
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56.7
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52.5
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50.8
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65.5
66.3
89.2
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66.4
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122.4
125.5
65.2
66.5
62.5
68.6
64.9
70.9
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73.8
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87.6
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93.2
122.8
112.5
115.5
139.6
133.0
152.9
123.1
163.9
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42.7
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81.3
77.071.0
73.0
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86.4
93.2
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164.6
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50
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150
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SETTENTRIONALE
SICULA
T E L E F O N
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BORRACCIO
S.P
.
N. 7
6
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CAPPUCCINI
S A N T ' A N N A
IL CARMINE
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BONOMO
CASA
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IDR
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S.P
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BARCELLONA
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Case study
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Case study
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.30 Case study
Flood inundation and propagation in the city were modeled using a 2D hydraulic modelbased on De Saint Venant equations previously calibrated using the observationsconcerning water depths and flow velocities.
2538000 2538500 2539000 2539500 2540000
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42.6
34.7
38.9
34.9
42.7
39.1
36.4
46.2
41.4 45.8
48.7
46.2
53.1
45.6
5087
42.5
39.8
44.3
45.0
39.2
40.2
37.9
37.8
63.9
47.7
50.5
68.0
140.8
98.6
66.8
135.5
81.5
131.2
139.7
144.3
113.0
172.8
174.8
159.2
104.4
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45.8
48.3
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95.7
105.8
107.7
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83.1
79.3
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120.681.7
73.6
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193.4
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107.9
139.8
80.2
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206.6
221.3
203.7
217.4
177.2
125.0
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133.5
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127.2
93.8
94.8
100.7
108.5
100.4
117.8132.8
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150
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K0
K1
K2
K3
S.P
.
N. 7
6
MONTE
CROCI
CHIESA
CAPPUCCINI
S A N T ' A N N A
BARCELLONA
POZZO DI
GOTTO
IL CARMINE
S.P
.
BARCELLONA
SAN
SAIA
SANTA
VENERA
SANTA VENERA
DEL PIANO
ZIGARI
NASARI
S E R R O
M I R A N D A
M O A S
D U
E
M U
L I N I
F E O
N. 8
2
LO
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AN
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0.3
0.8
1.3
1.8
2.3
2.8
3.3
3.8
4.3
4.8
5.3
0.2 to 0.5
0.5 to 1
1 to 1.5
1.5 to 2
2 to 2.5
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.31
Case study
Simulations have been carried out with flood barriers of
different heights, to find the optimum height, to prevent
overtopping.
The force acting on the barriers was calculated combining the
classical equations for hydrostatic and hydrodynamic
force on a plane surface along a vertical wall:
The forces resulted from the model have been compared
with the stability values of the barriers provided by the
producers.
Hydraulic and static verification
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FLOOD PANEL (U.S.A.)
FLOOD BREAK
(U.S.A.)
GEODESIGN
BARRIERS
(SWEDEN)
DUTCHDAM
(NETHERLANDS)
Case study
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Maximum flood force2353 N/m
Final results
Maximum resistance (N/m)
Flood Panel Flood Break Geodesign Barriers
6075 18564 3900
For 3 feet height barriers
• Purchasing and installation costs for Geodesign barrier are around500 euros per meter• The intervention will be implemented for 12 meters (road width)
with a final cost of 6000 euros
Case study
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Case study
Comparison of water depths values, before and after the intervention
0 2 4 6 8 10 12 14 160
0.1
0.2
0.3
0.4
0.5
0.6
0.7
distance(m)
heig
ht
of
wate
r(m
)
without flood barriers
with flood barriers
0 2 4 6 8 10 12 14 160.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
distance(m)
heig
ht
of
wate
r(m
)
without flood barriers
with flood barriers
0 2 4 6 8 10 12 14 160.2
0.25
0.3
0.35
0.4
0.45
0.5
distance(m)
heig
ht
of
wate
r(m
)
without flood barriers
with flood barriers
SectionA-A
SectionB-B
SectionC-C
hflood barriers = 1.25 m
Final results
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Velocity vectors without flood barriers Velocity vectors with flood barriers
Case study
Velocity fields
Final results
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Conclusions
The new policy of flood risk management is to give more attention to
non-structural measures, allowing people to “live with floods” rather
than “fight floods”.
Floodproofing can be defined as combination of structural and non-
structural changes, or adjustments made in the building that reduces or
prevents flood damage to the structure and/or its contents
Road bariers sasy to implement with low costs
Suitable also for fast flowing flooding events
Need to use detailed hydrodynamic model for barriers design
Thank you for your attention(garonica@unime.it)