going against the flow travel patterns in southern france: a vulnerability to flash floods
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Going against the flow Travel patterns in Southern France: A Vulnerability to flash floods. Isabelle RUIN ASP Post-Doc NCAR - [email protected]. 1- Statement of research problem 2- Objectives, study area and methods 3- Main results 4- Conclusion and looking ahead. - PowerPoint PPT PresentationTRANSCRIPT
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Going against the flow
Travel patterns in Southern France: A Vulnerability to flash floods
Isabelle RUIN ASP Post-Doc NCAR - [email protected]
1- Statement of research problem
2- Objectives, study area and
methods
3- Main results
4- Conclusion and looking ahead
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2
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1- Statement of research problem
Why people decide to travel in crisis situation?
Two assumptions:
➀ People’s unwillingness to change their daily routines
➁ Discrepancy between individual space-time representations and actual flash flood phenomenon characteristics
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2- Objectives of flash flood vulnerability assessment
2
1
3
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Study area and methods
Cognitive mapping sampling Questionnaires surveys
✓ 960 residents (quotas)✓ 260 tourists
Cognitive mapping
✓ 200 residents: spatially stratified sampling
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Study area
Post-flood investigations (2002, 2005)
✓30 in-depth interviews✓Analysis of loss of life circumstances ✓Observations during the crisis period
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3- Main results:
External factors
1. Spatio-temporal scales of Flash Floods
2. Road network exposure
3. Human exposure
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Spatio-temporal scales of Flash Floods
Source : Creutin, 2001
1 hour
1 day
Scale of hydrological responses
Scale of atmospheric objects (Orlanski, 1975)
Wate
rsh
ed
s t
ime
resp
on
ses (
mn
)
Flash Flood domain
2- Meso-scale convective system
Several hours
100 Km
2
1
1- Convective cell
10 Km
One hour
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Large road network exposure
Administrative area boundaryMain streamsTributariesToll motorwaysHighwaysSecondary roadsRoad’s sections regularly flooded
ALESALES
NIMESNIMES
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✓ 11 young individuals died in 9 watersheds smaller than 20 km2
✓ 11 old individuals died in 5 watersheds bigger than 1000 km2
Human exposure during the 2002 Flash flood event (1)Loss of life: hydrometeorological circumstances
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Extreme speed of watershed responses
Extremely short lead-time for
warnings
Human exposure during the 2002 Flash flood event (2) Loss of life: Warning efficiency
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3- Main results:
Internal factors
1. Motorists’ danger perceptions on daily itineraries
2. Perceptions of vulnerability
3. At-risk travel patterns in the Gard region
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Road network
✓ 29% of the road sections used by our sample are prone to flooding
The 2/3 are not considered as dangerous
Source : DDE30, Cognitive mapping survey, 2006. N = 200Ruin, 2007
Comparison between often flooded road sections and
risk perceptions
ALÈSALÈS
NIMESNIMESNIMESNIMES
Main streamsEast rural zoneSouth urban zoneWest rural zoneNorth urban zone
76 to 100% of users51 to 75% of users26 to 50% of users1 to 25% of users
Road sections prone to flooding
Road sections used and peceived as non dangerous
Road sections used and peceived as dangerous by:
Motorists’
danger
perception on
daily itineraries
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Perceptions of vulnerability
✓ Rapidity of watershed time response is mostly underestimated, specially for small catchments
✓ More than 60% ignore that 2 feet of moving water may sweep a car away while critical water depth for a person (to be knocked off their feet) is better evaluated
✓ Only 35% of the residents think Météo-France Orange alert is to a warning for fatal danger, but 55% associate it with danger on their own daily itinerary
Traveling during a flash flood event is known to be dangerous, but thresholds of dangerousness are hardly perceived
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East rural zoneSouth urban zoneWest rural zoneNorth urban zone
Main itineraries taken by the 200 interviewees
High rate usageMidle rate usageLow rate usageVery low rate usage
Source : DDE30, Cognitive mapping survey, 2006. N = 200
Ruin, 2007
NIMESNIMES
ALÈSALÈS➁
➁
➁ At-risk mobility of rural retired- 20% of the sample
- frequent but little hazardous travels - weak perception of risk on roads
Three kinds of at-risk mobility in the Gard area
➀ Commuting is highly risky- 30% of the sample
- frequent and highly hazardous
travels- weak perception of risk on roads
➀
➂ Inter-state mobility fairly risky- 10% of the sample
- unfrequent and fairly hazardous travels- weak perception of risk on roads
➂
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3- Main results:
Contextual factors
1. Influence of spatial and settings
2. Main constraints to evacuation
3. Main constraints to travel’s flexibility
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Influence of spatial and temporal settings
✓ Stakes located at the confluence of watersheds of different sizes
✓ Succession or simultaneity of flood peaks due to differences in catchment sizes
✓ Vulnerability variations within the time of the day, week, season...
16
Catchment
Hydographic network Catchment outletRelief
1000 km2
20 km2
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Main constraints to evacuation
✓ Afraid of spreading the family:
37% tourists
✓ Feeling of safety: 27% residents
✓ Afraid of leaving pets: 18%
residents
Afraid of spreading the family
Reasons for non-instant evacuation
No reason
Others
Handicap (me or relative’s)
Feeling of safety
Afraid to leave
pets
Afraid of spreading the family
Afraid of loosing goods
Don’t know
Residents (N=908)
Tourists (N=258)
Don’t know
Evacuation refusal
Wait and see
Look for information
Instant evacuation
Response to evacuation order
Residents (N=922)
Tourists (N=258)
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Réaction alors qu'une alerte est déclenchée pendant que les enfants sont à
l'école
46%
44%
4% 6%
Va immédiatement chercher ses enfantsrien, vous savez qu'ils sont pris en charge par l'étab.Demande à un parent ou ami d'aller les chercherAutres
Parental reaction to warnings when children are in schools
Immediatly pick up their childrenNothing, you know they are safe in school You ask a relative to pick them upOthers
Workers would
hardly cancel their
travels
Main constraints to travel’s flexibility
In reaction to warnings, 50% of
the parents would pick up their
children from school.
Responses to Météo-France watches (orange) and warnings (red) for heavy precipitations
Cancel Travels
Search information
Unchanged activities and/or travel patterns
WorkersResponse to orange alert
Non-workersResponse to red alert
Workers Non-workers
Mean deviation
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4- Conclusion and looking
ahead
1. Complementarity of qualitative and quantitive
methods in behavioral studies 2. Synthesis of vulnerability factors in crisis period
3. Research perspectives
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Complementarity of qualitative and quantitive methods in behavioral
studies
1- The cautious58 % (sample 2004)
2- Workers constrained by professional activities13 % (sample 2004)
Those avoiding evacuation
3 % (Sample. 2004)
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Synthesis of vulnerability factors in crisis period
• Age (< 25 / > 65 years
old)
• Gender
• Type of mobility
• New residents
• Language barrier
(tourists)
• Area of living (ZUsud)
• very small
catchments (< 20km2)
• Confluence of
watersheds of
differents sizes
• Time of impact: rush-
hours / night...
• Parental duty
• Professional activity
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1. Observe behaviors in both normal daily life and
extreme weather conditions
2. Organize extreme events post investigations
Research perspectives (1)
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Need for Behavioral
verification surveys to
assess adaptative capacities
of drivers in different
weather conditions:
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Research perspectives (2) :
Behavioral survey project: NCAR ASP proposal
(2008-2009)
1. Observe driver’s behavior at low water
crossings in Texas (Austin)
Quantitative survey:
• Use of video, car counting
Qualitative survey:
• Use Youtube video, travels
log and in-depth interviews
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Research perspectives (3) : DELUGE
network E. Gruntfest submitted NSF proposal (2008-2013)2. Disasters: Evolving Lessons Using Global
Experience
Focus on post-event field studies for floods to maximize interactions between social scientists, hydrologists and meteorologists
New guidelines on post-event investigations for use by integrated teams of physical scientists, social scientists, and practitioners.
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Thank youThank you