Going against the flow Travel patterns in Southern France: A Vulnerability to flash floods

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Going against the flowTravel patterns in
Southern France A Vulnerability to flash floods
Isabelle RUIN ASP Post-Doc NCAR - isar_at_ucar.edu
1- Statement of research problem 2- Objectives,
study area and methods 3- Main results 4-
Conclusion and looking ahead
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1- Statement of research problem

• Why people decide to travel in crisis situation?
  
• Two assumptions
• ? Peoples unwillingness to change their daily
  routines
• ? Discrepancy between individual space-time
  representations and actual flash flood phenomenon
  characteristics

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2- Objectives of flash flood vulnerability
assessment
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Study area and methods
Study area
Source IGN - GEOFLA Départements Réalisation
L. Avvenengo Ducca, 2006

• Post-flood investigations (2002, 2005)
• 30 in-depth interviews
• Analysis of loss of life circumstances
• Observations during the crisis period

• Questionnaires surveys
• 960 residents (quotas)
• 260 tourists
• Cognitive mapping
• 200 residents spatially stratified sampling

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3- Main resultsExternal 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
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Large road network exposure
ALES
NIMES
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Human exposure during the 2002 Flash flood event
(1)Loss of life hydrometeorological
circumstances

• 11 young individuals died in 9 watersheds
  smaller than 20 km2
• 11 old individuals died in 5 watersheds bigger
  than 1000 km2

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Human exposure during the 2002 Flash flood event
(2) Loss of life Warning efficiency
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3- Main resultsInternal 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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Motorists danger perception on daily itineraries
Comparison between often flooded road sections
and risk perceptions
ALÈS

• 29 of the road sections used by our sample are
  prone to flooding
• The 2/3 are not considered as dangerous

Main streams East rural zone South urban
zone West rural zone North urban zone
NIMES
Road network
Source DDE30, Cognitive mapping survey, 2006. N
200 Ruin, 2007
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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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Three kinds of at-risk mobility in the Gard area
ALÈS
NIMES
Source DDE30, Cognitive mapping survey, 2006. N
200 Ruin, 2007
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3- Main resultsContextual factors

1. Influence of spatial and settings
2. Main constraints to evacuation
3. Main constraints to travels 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...

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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
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Main constraints to travels flexibility

• In reaction to warnings, 50 of the parents
  would pick up their children from school.

• Workers would hardly cancel their travels

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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
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Synthesis of vulnerability factors in crisis
period
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Research perspectives (1)

• Need for Behavioral verification surveys to
  assess adaptative capacities of drivers in
  different weather conditions

1. Observe behaviors in both normal daily life and
   extreme weather conditions
2. Organize extreme events post investigations

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Research perspectives (2) Behavioral survey
project NCAR ASP proposal (2008-2009)

1. Observe drivers 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 you