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CNR: Alamanacco della Scienza


N. 19 - 23 nov 2011
ISSN 2037-4801

International info   a cura di Cecilia Migali


Real time floods forecasts  

In recent years, the interest in the prediction and prevention of natural hazards, related to hydro-meteorological events, has increased the challenge for numerical weather modelling, in particular for limited area models, to improve the quantitative precipitation forecasts for hydrological purposes. In this framework, Cnr-Water Research Institute (Irsa) is organizing a seminar on 30 November 2011, during which Alessandro Ceppi, researcher at the Politecnico of Milano will be present a real-time flood forecasting system for Alpine basins with a hydro-meteorological operational alert procedure.

The hydro-meteorological chain includes both probabilistic forecasting based on ensemble prediction systems with a lead time of a few days, and short-range forecasts based on a high resolution deterministic atmospheric model. The hydrological model used to simulate runoff was developed at Politecnico di Milano. The analysis focuses on the Maggiore Lake basins, located in the North-West Italy and Southern Switzerland, and on the Piedmont mountain watersheds faced to Alps and Apennines.

The aim of the work is to assess the reliability of a real time flood forecasting system, coupling meteorological and hydrological models, analysing the forecasting precipitation and temperature fields at different spatial scales, and in different weather conditions.  In particular, two events are analysed to show the effect of the meteorological models spatial resolution on discharge forecasts over mountainbasins (the June 2007 convective event), and how the effect of the initial conditions of soil moisture can influence meteorological warnings (the November 2007 event). Afterwards, further analyses were carried out in order to investigate different sources of uncertainties that can affect the quantitative discharge forecast in mountain catchments. Since the forecasting methodology is conditioned by hydrological model performance, but above all by atmospheric forcing inputs, researchers showed how a forecasted temperature error with a significant snow line (the November 2008 event), drastically influences the whole forecasting cascade chain over Alpine basins.

According to the researchers, the use of earlywarning systems seem to be promising in terms of predicting possible river floods in advance with a lead time of 24-48 hours before the main peak flow, as highlighted in the case study over the Stura di Demonte basin in May 2008 and in the last flood of the River Seveso that occurred in September 2010 in Milan.

Fonte: Gianni Tartari, Istituto di ricerca sulle acque, Brugherio, tel. +39 039 21694203, email tartari@irsa.cnr.it