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Thursday 12 May 2016Statistical Science Seminar: Regional flood frequency analysis for Norway

Thirds Thorarinsdottir -

H101 14:30-16:30

In Norway, hydropower comprises 95% of the total electricity generation

with over 2300 classified dams connected to the power

production. Extreme flooding and dam safety are thus important societal

issues. The aim of flood frequency analysis is to estimate streamflow

quantiles, or design floods, for given exceedance probabilities or

return periods, e.g. the 100-year flood. Design flood estimation forms

the basis for hazard management related to flood risk and is a legal

obligation when building infrastructure such as dams, bridges and roads

close to water bodies. The streamflow quantile estimates required for

these applications might range from an estimate of the index flood, or

the mean annual flood, to quantiles higher than the 1000-year flood.

Furthermore, applications commonly require design flood estimates at

locations for which only a short series of discharge data is available.

To this end, we propose a regional flood estimation approach based on

the general extreme value (GEV) distribution where the parameters of the

distribution depend on meteorological, hydrological and geographical

information for the catchment. Estimation in the model is performed via

Bayesian model averaging resulting in a mixture of models where the

different mixture components vary in the particular covariates used for

each model parameter. Additionally, we discuss approaches for verifying

frequency analysis models and pose some questions in this regard.

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