Abstract
Abstract. This paper concerns the analysis of the 1 October 2009 flash flood and debris flow event caused by a very intense rainfall concentrated over the Messina area. The storm caused severe flash floods in many villages around the city of Messina, such as Giampilieri, Scaletta Zanclea, Altolia Superiore and Molino, with 38 casualties and significant damages to property, buildings, roads and bridges estimated close to 550 million Euro. The main focus of this work is to perform a post event analysis, putting together available meteorological and hydrological data in order to get better insight into temporal and spatial variability of the rain storm, the soil moisture conditions and the consequent flash flood in the Giampilieri catchment. The event was investigated using observed data from a raingauge network. Statistical analysis using GEV distribution was performed and rainfall return period (storm severity) was estimated. Further, measured rainfall data and rainfall-runoff modelling were used to estimate soil moisture conditions, to analyse the hydrological behaviour and to reconstruct flood hydrograph. With the help of GIS technology and particularly spatial analysis, the volume of debris which has gone down into the Giampilieri village was also calculated. GIS maps with landslide and material deposit areas were produced and analysed.
Highlights
A flash flood is defined as a flood which follows shortly after a heavy or excessive rainfall event (Georgakakos, 1986; Sweeney, 1992; Borga et al, 2007) and the important hydrologic processes are occurring on the same spatial and temporal scale as the intense precipitation
Past flash floods and debris flow have often caused high numbers of casualties; over 80 people, for example, lost their lives in the 1996 Biescas flood in Spain (Alcoverro et al, 1999), 47 people died in the flash flood on the Mala Svinka River in Slovakia in 1998, 23 people lost their lives in the Gard 2002 flood, 2 people died in the flash flood and debris flow on Cable Canyon in San Bernardino County in California in 2003 (USGS, 2005) and 19 000 people lost their lives in the Cordillera de la Costa, Vargas (Venezuela) flash flood and debris flow disaster in 1999 (USGS, 2001)
In the rainfall generator module, the rainfall are dealing with an ungauged catchment, the choice was orientated towards the use of a simple lumped rainfall-runoff model based on the Instantaneous Unit Hydrograph IUH for was assumed to follow the two components extreme value (TCEV) distribution whose parameters were estimated at regional scale for Sicily
Summary
A flash flood is defined as a flood which follows shortly (i.e. within a few hours) after a heavy or excessive rainfall event (Georgakakos, 1986; Sweeney, 1992; Borga et al, 2007) and the important hydrologic processes are occurring on the same spatial and temporal scale as the intense precipitation. 400 During this last event, a devastating flooding was caused by a very intense rainfall concentrated over Sicily affecting the area of Messina and being responsible for the destruction of numerous structures and goods and Giampilieri Superiore village for 38 casualties. During the course of the event, the persisting rainfall in the Ionian Sea coast around Messina caused a number of landslides, flash floods and debris flow that blocked the road system as well as the railway and the motorway, making the already critical state caused by the adverse weather conditions of the last half of September worse. Rainfall maps (Fig. 6), derived by interpolating available data through kriging, show how the storm covered the southern part of the city of Messina and was concentrated on the Ionian Sea coast and mainly in the area around Giampilieri. 14.00 16.00 18.00 20.00 22.00 0.00 2 Fig. 8. 10-min rainfall intensity recorded at the raingauge stations
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