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| Titel |
Influence of rainfall spatial resolution on flash flood modelling |
| VerfasserIn |
M. Sangati, M. Borga |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 9, no. 2 ; Nr. 9, no. 2 (2009-04-09), S.575-584 |
| Datensatznummer |
250006723
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| Publikation (Nr.) |
 copernicus.org/nhess-9-575-2009.pdf |
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| Zusammenfassung |
| High resolution radar rainfall fields and a distributed hydrologic model are
used to evaluate the sensitivity of flash flood simulations to spatial
aggregation of rainfall at catchment scales ranging from 10.5 km2 to
623 km2. The case study focuses on the extreme flash flood occurred on
29 August 2003 on the eastern Italian Alps. Four rainfall spatial
resolutions are considered, with grid size equal to 1-, 4-, 8- and 16-km.
The influence of rainfall spatial aggregation is examined by using the flow
distance as a spatial coordinate, hence emphasising the role of river
network in the averaging of space-time rainfall. Effects of rainfall spatial
aggregation are quantified by using a dimensionless parameter, represented
by the ratio of rainfall resolution (Lr) to the characteristic basin
length (Lw), taken as the square root of the watershed area. Increasing
the Lr/Lw parameter induces large errors on the simulated peak
discharge, with values of the peak discharge error up to 0.33 for
Lr/Lw equal to 1.0. An important error source related to spatial
rainfall aggregation is the rainfall volume error caused by incorrectly
smoothing the rainfall volume either inside or outside of of the watershed.
It is found that for Lr/Lw 1.0, around 50% of the peak
discharge error is due to the rainfall volume error. Remaining errors are
due to both the distortion of the rainfall spatial distribution, measured
with respect to the river network, and to the reduced spatial variability of
the rainfield. Further investigations are required to isolate and examine
the effect of river network geometry on the averaging of space-time rainfall
at various aggregation lengths and on simulated peak discharges. |
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