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| Titel |
Spatial moments of catchment rainfall and their use to quantify the influence of spatial rainfall variability on runoff response |
| VerfasserIn |
Paolo Tarolli, Davide Zoccatelli, Daniele Penna, Marco Borga |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250044195
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| Zusammenfassung |
| The concept of flow distance, i.e. the distance along the runoff flow path from a given point to
the outlet, provides a natural metric to examine the spatial rainfall distribution, as already
been observed by Woods and Sivapalan (1999). Variability measures based on this metric
may be particularly useful when examining the influence of spatial rainfall variability on
flood response modelling. Linear runoff routing through branched channel networks imposes
an effective averaging of spatial rainfall excess at equal flow distance, in spite of the inherent
spatial variability. This implies that rainfall organisation measured along the river
network by using the flow distance coordinate may be a significant property of rainfall
spatial variability when considering flood response modelling. Spatial moments of
catchment rainfalls provide a description of overall spatial rainfall organisation, as
a function of the rainfall field R(u) value at position u and of the flow distance
d(u) between the position u and the catchment outlet measured along the river
network. The principal objectives of this work are: (1) to investigate the statistical
properties of the spatial moments of catchment rainfall; (2) to analyse the use of these
moments to quantify the sensitivity of distributed rainfall-runoff models to rainfall
spatial variability; and (3) to examine the dependence of the spatial moments of
rainfall catchment on the relative contribution of hillslope and channels to the average
response time. The investigation focuses on a set of 25 extreme flash flood events
observed across Europe during the period 1994-2007 for which high-resolution data
enabling identification and analysis of the hydrometeorological causative processes
(including high quality radar rainfall observations) have been collected. The size of the
study catchments range from 36 to 2000 km2. The analysis reported here shows that
neglecting the spatial rainfall variability results in a considerable loss of simulation
Nash-Sutcliffe (NS) efficiency even for catchment less than 100 km2 in size. Moreover, it is
shown that these rainfall statistics, used in combination, are able to isolate and
describe the features of rainfall spatial variability which have significant impact on
runoff simulation. The analysis shows also that increasing the hillslope contribution
to the overall response time decreases the runoff response modeling sensitivity
to spatial rainfall variability. These characteristics are emphasized in elongated
catchments and for cases of strong convection enhanced by orographic uplifting. |
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