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| Titel |
Levee breaches and uncertainty in flood risk mapping |
| VerfasserIn |
Roberto Ranzi, Stefano Barontini, Michele Ferri, Baldassare Bacchi |
| 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 |
250043836
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| Zusammenfassung |
| Due to the dense anthropization, to the agricultural and industrial exploitation and to its
treasures of art and history, northern Italy floodplain, which is a result of the action of the
rivers draining into the northern Adriatic sea, is a land where the mitigation of the flooding
risk rises at crucial importance. Most of the major rivers flowing in this area have a long and
complex history of training in order to protect the plain and the cities and it is difficult to
predict the position where levee breaches can occur and the width and depth of the
breaches.
In view of an investigation on the uncertainties in flood risk mapping, with the aim of
developing a methodology based on a stocastic approach to model the position, length and
depth of the breach coupled with a simplified method to determine the flooded area, we
collected information on major floods and statistics of levees breaches occurred in the Po,
Adige, Brenta, Piave and Tagliamento rivers. We provide the statistics of 225 historical
breaches occurred in the 1801—2000 time windows in the floodplain course of the Po river,
which is 324 km long (from upstream to downstream, 80 km are meandering, 100 km are
braided and the others are sinuous–straight). The first two stretches are characterised also by
lateral inflow, while the last stretch is mainly characterised by routing and floodplain
inundation processes.
Three dominant levee collapse mechanisms (overtopping, erosion, piping) were
considered. The highest number of breaches was registered in the meandering course, with
overtopping strongly (78%) as the most frequent dominant mechanism. Three different
samples of historical floods were considered, separated by two important floods
(1857 and 1879). A significant decrease in the total number of breaches (per year
and per kilometer) was observed since the second half of the 19th century, as a
consequence of flood directives issued in that period and to the levees restoration after
the floods. A decrease in the percentage of the overtopping was observed in the
second period (77% in the first half of the 19th century, 56% in the 1857—1879
window and again 74% up to the 1951 flood) jointly to the increasing of piping
(respectively 9%, 32% and 18% in the three time windows). Statistics on the breach
occurrences in the Adige, Brenta, Piave and Tagliamento rivers are also presented and
discussed. |
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