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

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

2. 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 2

3. 2 1 3 2- Objectives of flash flood vulnerability assessment

4. Study area Cognitive mapping sampling Study area and methods 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

5. 3- Main results:External factors • Spatio-temporal scales of Flash Floods • Road network exposure • Human exposure

6. 100 Km 2- Meso-scale convective system 1- Convective cell 1 2 1 day One hour Several hours 10 Km 1 hour Watersheds time responses (mn) Flash Flood domain Scale of hydrological responses Scale of atmospheric objects (Orlanski, 1975) Spatio-temporal scales of Flash Floods Source : Creutin, 2001

7. Administrative area boundary Main streams Tributaries Toll motorways Highways Secondary roads Road’s sections regularly flooded Large road network exposure ALES NIMES

8. 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

9. 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

10. 3- Main results:Internal factors • Motorists’ danger perceptions on daily itineraries • Perceptions of vulnerability • At-risk travel patterns in the Gard region

11. Road sections prone to flooding Road sections used and peceived as non dangerous Road sections used and peceived as dangerous by: 76 to 100% of users 51 to 75% of users 26 to 50% of users 1 to 25% of users Comparison between often flooded road sections and risk perceptions Motorists’ danger perception on daily itineraries 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

12. 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

13. ➁ ➁ ➂ ➀ • ➀ Commuting is highly risky • 30% of the sample • frequent and highly hazardous travels • weak perception of risk on roads • ➁At-risk mobility of rural retired • 20% of the sample • frequent but little hazardous travels • weak perception of risk on roads • ➂Inter-state mobility fairly risky • 10% of the sample • unfrequent and fairly hazardous travels • weak perception of risk on roads East rural zone South urban zone West rural zone North urban zone Main itineraries taken by the 200 interviewees High rate usage Midle rate usage Low rate usage Very low rate usage Three kinds of at-risk mobility in the Gard area ALÈS NIMES Source : DDE30, Cognitive mapping survey, 2006. N = 200 Ruin, 2007

14. 3- Main results:Contextual factors • Influence of spatial and settings • Main constraints to evacuation • Main constraints to travel’s flexibility

15. Catchment outlet Catchment Hydographic network Relief 1000 km2 20 km2 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

16. Response to evacuation order Don’t know Evacuation refusal Wait and see Look for information Instant evacuation Reasons for non-instant evacuation Feeling of safety Tourists (N=258) Residents (N=922) Afraid to leave pets Handicap (me or relative’s) Afraid of spreading the family No reason Others Afraid of loosing goods Don’t know Tourists (N=258) Residents (N=908) 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

17. Parental reaction to warnings when children are in schools Immediatly pick up their children Nothing, you know they are safe in school You ask a relative to pick them up Others Responses to Météo-France watches (orange) and warnings (red) for heavy precipitations Cancel Travels Search information Unchanged activities and/or travel patterns Mean deviation Response to orange alert Response to red alert Workers Non-workers Workers Non-workers Main constraints to travel’s flexibility • In reaction to warnings, 50% of the parents would pick up their children from school. • Workers would hardly cancel their travels

18. 4- Conclusion and looking ahead • Complementarity of qualitative and quantitive methods in behavioral studies • Synthesis of vulnerability factors in crisis period • Research perspectives

19. Those avoiding evacuation 3 % (Sample. 2004) 2- Workers constrained by professional activities 13 % (sample 2004) 1- The cautious 58 % (sample 2004) Complementarity of qualitative and quantitive methods in behavioral studies

20. very small catchments (< 20km2) • Confluence of watersheds of differents sizes • Time of impact: rush-hours / night... • Parental duty • Professional activity • Age (< 25 / > 65 years old) • Gender • Type of mobility • New residents • Language barrier (tourists) • Area of living (ZUsud) Synthesis of vulnerability factors in crisis period

21. Research perspectives (1) • Need for Behavioral verification surveys to assess adaptative capacities of drivers in different weather conditions: Observe behaviors in both normal daily life and extreme weather conditions Organize extreme events post investigations

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

23. 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.

24. Thank you