Forecasting flash flood impacts integrating the space-time distribution of social vulnerability
Supervision:
LTHE: Isabelle Ruin – Sandrine Anquetin (HDR)
NOAA-NSSL (Norman, Oklahoma): Jonathan J. Gourley
If you have ever attempted to hand contour a map of damage from flash flooding, you will quickly
discover the influence of surface controls, which create discontinuous and untidy contours. Low-water
crossings, infrastructure built in close proximity to streams, normally dry riverbeds in populated zones,
and roads in low-lying areas are all examples of anthropogenic factors that increase societal
susceptibility to flash flooding.
In addition, impacts in terms of loss of life are very much related to the space-time distribution of the
everyday life social activity. In fact, in such fast evolving events impacts depend not just on such
compositional variables as the magnitude of the flood event and the vulnerability of those affected,
but also on such contextual factors as its location and timing. Those contextual factors can alter the
scale and social distribution of impacts and vulnerability to them. In the case of flooding fatalities, for
instance, the elderly are often said to be the most vulnerable, but when fatalities are mapped against
basin size and response time, it has been shown that in fact it is young motorist who are most likely to
be killed in flash flooding of small catchments, whereas the elderly most frequently perish in their
homes from large scale fluvial flooding (Ruin et al., 2008).
Unfortunately, tools commonly used to monitor and predict flash flooding, including sophisticated
distributed hydrologic models, rarely incorporate any information about anthropogenic vulnerability
factors and never envisage the dynamic nature of the exposition of the population to such fast
evolving events.
This research will rely on impact data analysis coming from a detailed impact classification and
analysis of flash flood reports from the National Weather Service (NWS) Storm Data and Severe
Hazards Analysis and Verification Experiment (SHAVE) conducted at the National Severe Storms
Laboratory (NSSL) in Norman, Oklahoma.
As a first step, the US Flash Flood impact Database (Gourley et al., 2013) will be analyzed to test two
main hypotheses:
a) The flooding of small catchments (< 20 km2) is mostly associated with punctual inundation of
the road network, vehicle-related and “open-air” fatalities of young to middle-aged adults.
On the other hand, large hydrological scales (> 1000 km2) are responsible for building
damages, evacuations and inside drowning of elderly or physically vulnerable populations.
b) The spatial distribution and loss-of-life circumstances are related to the flood timing and the
diurnal rhythms of the social activities. For instance, vehicle-related fatalities or rescues are
expected to be more frequent when a flood event happens during rush hours when
everyone is driving than when it happens during working hours. On the contrary, during
night hours, less people are usually exposed to road flooding but the poor visibility makes
people more vulnerable to hazardous circumstances.
In a second step, a small number of representative flash flood events (in terms of timing, hydro-
meteorological and socio-demographical contexts) will be extracted from the database to be further
analyzed. Those events will be used as case studies to:
1) Implement two types of distributed hydrological models: i) the French CVN model described by
Braud et al. (2010) and developed at the LTHE (Grenoble University); the Ensemble Framework
For Flash Flood Forecasting (EF5) model developed by the University of Oklahoma and the NSSL
at the National Weather Center;
2) Identify space-time flash flood vulnerability patterns using GIS layers of road networks,
population density, stream locations, elevation, degree of imperviousness (urbanization), land
use, etc. (Calianno et al, 2012b);
3) Combine the space-time vulnerability indices with the distributed hydrologic models to test the
efficacy of such integrated models in reproducing the impacts of the selected past catastrophic
events.
This interdisciplinary research will take place in the context of a collaboration between Jonathan J.
Gourley, NOAA research hydrologist of the National Severe Storms Laboratory (NSSL) at the National
Weather Center (NWC) in Norman (Oklahoma, USA), and CNRS researchers’ Sandrine Anquetin, hydrometeorologist and Isabelle Ruin, human geographer both from the Laboratoire d’étude des Transferts
en Hydrologie et Environnement (LTHE) at Grenoble University (France). Until now this collaboration
has taken the form of Master students exchanges and teaching experiences concluded by the
publication of three peer-reviewed papers (Ruin et al., 2012; Calianno et al., 2012; Gourley et al.,
2013).
The “delivrables” of this PhD work are twofold:
- Building and validating flash flood impacts forecasting tools based on existing US databases and
envisage the transferability of the methodology in a the French Mediterranean context;
- Intensifying and strengthening interdisciplinary research in an international environment.
References
Braud, I., Roux, H., Anquetin, S., Maubourguet, M. M., Manus, C., Viallet, P., & Dartus, D. (2010). The
use of distributed hydrological models for the Gard 2002 flash flood event: Analysis of associated
hydrological processes. Journal of Hydrology, 394(1), 162-181.
Calianno, M., Gourley, J. J., & Ruin, I. (2012b). Forecasting flash flood impacts utilizing anthropogenic
exposure factors. Poster presented at ERAD, Toulouse, June 24-29 2012.
Calianno, M., Ruin, I., & Gourley, J. J. (2012). Supplementing flash flood reports with impact
classifications. Journal of Hydrology.
Gourley, J. J., Hong, Y., Flamig, Z. L., Arthur, A., Clark, R., Calianno, M., ... & Krajewski, W. F. (2013). A
Unified Flash Flood Database over the US. Bulletin of the American Meteorological Society.
Ruin, I., Creutin, J. D., Anquetin, S., & Lutoff, C. (2008). Human exposure to flash floods–Relation
between flood parameters and human vulnerability during a storm of September 2002 in Southern
France. Journal of Hydrology, 361(1), 199-213.
Ruin, I., Lutoff, C., Creton-Cazanave, L., Anquetin, S., Borga, M., Chardonnel, S., ... & Thielen, J. (2012).
Toward a Space-Time Framework for Integrated Water and Society Studies. Bulletin of the
American Meteorological Society.
Profil candidat recherché
Le candidat devra être titulaire d’un Master 2 en Sciences de l’eau ou Sciences de la Terre /
Géographie ou diplôme équivalent.
Un intérêt pour la question des risques hydro-météorologiques et des approches interdisciplinaires
constitueraient un atout.
Compétences techniques souhaitées
- Aptitude à la programmation
- Maitrise de logiciels de traitement statistique et système d’information géographique
- Très bonne maitrise de l’anglais
Cadre Scientifique de la thèse
La thèse sera menée au LTHE et, en particulier, dans l’équipe Hydrométéorologie, Climat et Impacts.
Cette recherche interdisciplinaire s’inscrit dans la dynamique du récent recrutement d’Isabelle Ruin
par la section Interdisciplinaire du CNRS (Section 45). Cette recherche se positionne dans un cadre
d’analyse en échelle spatiale et temporelle, que nous promouvons à travers i) des séminaires
interdisciplinaires à Grenoble, ii) des cours en Master STE-ECE, parcours international HYDROHASARDS
et dans le cadre des cours des écoles doctorales TUE et SMTP de Grenoble, et iii) à l’échelle
internationale, dans le cadre d’écoles thématiques “Weather and Society” dont la prochaine est
prévue en mai 2014 à l’Ecole de Physique des Houches.
Cette thèse de doctorat sera menée en partenariat étroit avec Jonathan J. Gourley, co-directeur de la
thèse que l’on souhaite proposer en cotutelle. Jonathan J. Gourley est hydrologue à la NOAA au
laboratoire National Severe Storms Laboratory (NSSL) du National Weather Center (NWC) à Norman
(Oklahoma, USA).