Abstract
The work aims at analyzing the bivariate relationship between flood peaks
and flood volumes, with a particular focus on the type and seasonality of
flood generation processes. Instead of the usual approach that deals with an
analysis of the annual maxima of flood events, the current analysis includes
all independent flood events in a catchment. Flood events are considered
independent when they originate from distinguishably different
synoptic/meteorological situations. The target region is located in the
northern part of Austria, and consists of 72 small and mid-sized catchments.
On the basis of the discharge measurements with a time resolution of 1 h
from the period 1976–2007, independent flood events were identified and were
assigned to one of the three following flood generation type categories:
synoptic floods, flash floods and snowmelt floods. These were subsequently
divided into two seasons, thereby separating predominantly rainfall-fed and
snowmelt-fed floods. Nine frequently-used copula types were locally fitted
to the samples of the flood type and seasonal data. Their goodness-of-fit
was examined locally as well as analyzed in a regional scope. It was
concluded that (i) treating flood processes separately is beneficial for the
statistical analysis; (ii) suitability patterns of acceptable copula types
are distinguishably different for the seasons/flood types considered, (iii)
the Clayton and Joe copulas shows an unacceptable performance for all the
seasons/flood types in the region; (iv) the rejection rate of the other
copula types depends on the season/flood type and also on the sample size;
(v) given that usually more than one statistically suitable dependence model
exists, an uncertainty analysis of the design values in the engineering
studies resulting from the choice of model seems unavoidable; (vi) reducing
uncertainty in the choice of model could be attempted by a deeper
hydrological analysis of the dependence structure between flood peaks and
volumes in order to give hydrological support to the decision on model's
suitability in specific regions and for typical flood generation mechanisms.
Citation
ID:
157378
Ref Key:
szolgay2015proceedingsa