A regional look at the selection of a process-oriented model for flood peak/volume relationships
Other literature type
(issn: 2199-899X, eissn: 2199-899X)
Recent research on the bivariate flood peak/volume frequency analysis has
mainly focused on the statistical aspects of the use of various copula
models. The interplay of climatic and catchment processes in discriminating
among these models has attracted less interest. In the paper we analyse the
influence of climatic and hydrological controls on flood peak and volume
relationships and their models, which are based on the concept of
comparative hydrology in the catchments of a selected region in Austria.
Independent flood events have been isolated and assigned to one of the three
types of flood processes: synoptic floods, flash floods and snowmelt floods.
First, empirical copulas are regionally compared in order to verify whether
any flood processes are discernible in terms of the corresponding bivariate
flood-peak relationships. Next the types of copulas, which are frequently
used in hydrology are fitted, and their goodness-of-fit is examined in a
regional scope. The spatial similarity of copulas and their rejection rate,
depending on the flood type, region, and sample size are examined, too. In
particular, the most remarkable difference is observed between flash floods
and the other two types of flood. It is concluded that treating flood
processes separately in such an analysis is beneficial, both hydrologically
and statistically, since flood processes and the relationships associated
with them are discernible both locally and regionally in the pilot region.
However, uncertainties inherent in the copula-based bivariate frequency
analysis itself (caused, among others, also by the relatively small sample
sizes for consistent copula model selection, upper tail dependence
characterization and reliable predictions) may not be overcome in the scope
of such a regional comparative analysis.