Vk. Gupta et Dr. Dawdy, PHYSICAL INTERPRETATIONS OF REGIONAL VARIATIONS IN THE SCALING EXPONENTS OF FLOOD QUANTILES, Hydrological processes, 9(3-4), 1995, pp. 347-361
The concepts of simple scaling and multiscaling provide a new theoreti
cal framework for the study of spatial or regional flood frequency rel
ations and their underlying physical generating mechanisms. In particu
lar, the scaling exponents in the power law relationship between flood
quantiles and drainage areas contain a 'basic signature of invariance
' regarding the spatial variability of floods, and therefore suggest d
ifferent hypotheses regarding their physical generating mechanisms. If
regional floods obey simple scaling, then the slopes do not vary with
return periods. On the other hand, if regional floods obey multiscali
ng, then the slopes vary with return periods in a systematic manner. T
his premise is expanded here by investigating the empirical variations
in the scaling exponents in three states of the USA: New York, New Me
xico and Utah. Distinct variations are observed in the exponents among
several regions within each state. These variations provide clear emp
irical evidence for the presence of both simple scaling and multiscali
ng in regional floods. They suggest that snowmelt-generated floods exh
ibit simple scaling, whereas rainfall-generated floods exhibit multisc
aling. Results from a simple rainfall-runoff experiment, along with th
e current research on the spatial scaling structure of mesoscale rainf
all, are used to give additional support to these physical hypotheses
underlying two different scaling structures observed in floods. In add
ition, the rainfall-runoff experiment suggests that the behaviour of t
he flood exponents in small basins is determined by basin response rat
her than precipitation input. This finding supports the existence of a
critical drainage area, as has been reported for the Appalachia flood
data in the USA, such that the spatial variability in floods in basin
s larger than the critical size is determined by the precipitation inp
ut, and in basins smaller than the critical size is determined by the
basin response.