IWRA Executive Office

OS3g Climate change: disasters and extreme events

abstract 84

Impact of climate change on hydrological risks

Author(s): Philippe Cantet, Patrick Arnaud
CEMAGREF, 3275 route de Cézanne CS 40061, 13182 Aix-en- Provence, Cedex 5.

Keyword(s): climatic changes, hourly rainfall generation model, rainfall-flow model, hydrologic risks

Article:

Poster:

Session: OS3g Climate change: disasters and extreme events

AbstractNowadays, climate changes are widely considered a reality by scientists (IPCC,

2001). Since the preindustrial period, observations have shown a significant evolution of mean annual pluviometry

(higher or lower depending on the geographical area). Nevertheless, scientists cannot easily evaluate its impact on

the extreme hydrometeorologic phenomena using classical statistical techniques. This problem comes from a lack of

distancing in the observed rain event time series to evaluate the tendency of extreme phenomena. Besides, global

climatic models show many difficulties in modelling extreme meteorological processes. Only studying the flow is not

sufficient because of changes in basin, independently of climate change (urbanisation, fire, deforestation, hydraulic

installations…). An original approach to study climate change is proposed by modelling flood generator processes

using an hourly rainfall generation model adapted to different climates [1] coupled with rainfall-runoff modelisation

[2].

The main objective of the research is to evaluate, by rainfall-runoff modelisations, which impacts climate

changes might have on floods. For example, evolution of climatic boundaries, which are important in the translation in

hydrologic risks, will be studied.

To show the detection of climate changes, parameters of the rainfall stochastic

generator are evaluated from many ranges of time and calculated by different statistical tests. In contrast to classical

methods, the model parameters are calculated by mean climatic characteristics and not by extreme values. So the

three parameters: occurrences of events, duration of events, and the intensity of rainfall, which are particularly well

adapted to examine rain signals, are not sensitive to the sample. By the variability of the characteristics of rain

detected by chronicles of observed rainfalls or anticipated by atmospheric models and by rainfall-flow modelisation,

impacts on hydrological risk are studied. Moreover, tests on future scenarios are possible, to evaluate the impact of

climate changes and also of landscape use. Our previous research has allowed us to product climatic typology of

rainfall by using model parameter settings. The rainfall and rainfall-runoff models have already been regionalised, with

actual climate hypothesis, on the part of French territory, but also on the Italian piemont , in a Spanish region, in the

Caribbean and on Reunion Island. On these territories, the cartographic evolution of hydrologic risk can be

evaluated with climatic change hypothesis.

References:

[1] Arnaud P., Fine J.A., Lavabre J., 2007. An

hourly rainfall generation model adapted to all types of climate. Accepted in Atmospheric Research.
[2] Arnaud

P., Lavabre J., 2002. Coupled rainfall model and discharge model for flood frequency estimation. Water Resources

Research, 38(6) 1075-1085.

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Impact of climate change on hydrological risks