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.

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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

Going against the flowTravel 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


1 statement of research problem

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


2 objectives of flash flood vulnerability assessment

2

1

3

2- Objectives of flash flood vulnerability assessment


Study area and methods

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


3 main results external factors

3- Main results:External factors

  • Spatio-temporal scales of Flash Floods

  • Road network exposure

  • Human exposure


Spatio temporal scales of flash floods

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


Going against the flow travel patterns in southern france a vulnerability to flash floods

Administrative area boundary

Main streams

Tributaries

Toll motorways

Highways

Secondary roads

Road’s sections regularly flooded

Large road network exposure

ALES

NIMES


Human exposure during the 2002 flash flood event 1 loss of life hydrometeorological circumstances

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


Human exposure during the 2002 flash flood event 2 loss of life warning efficiency

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


3 main results internal factors

3- Main results:Internal factors

  • Motorists’ danger perceptions on daily itineraries

  • Perceptions of vulnerability

  • At-risk travel patterns in the Gard region


Motorists danger perception on daily itineraries

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


Perceptions of vulnerability

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


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

  • 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


3 main results contextual factors

3- Main results:Contextual factors

  • Influence of spatial and settings

  • Main constraints to evacuation

  • Main constraints to travel’s flexibility


Influence of spatial and temporal settings

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


Main constraints to evacuation

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


Main constraints to travel s flexibility

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


4 conclusion and looking ahead

4- Conclusion and looking ahead

  • Complementarity of qualitative and quantitive methods in behavioral studies

  • Synthesis of vulnerability factors in crisis period

  • Research perspectives


Going against the flow travel patterns in southern france a vulnerability to flash floods

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


Synthesis of vulnerability factors in crisis period

  • 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


Going against the flow travel patterns in southern france a vulnerability to flash floods

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


Going against the flow travel patterns in southern france a vulnerability to flash floods

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


Going against the flow travel patterns in southern france a vulnerability to flash floods

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.


Going against the flow travel patterns in southern france a vulnerability to flash floods

Thank you


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