1,721,005 research outputs found
Metodi statistici e matematici per l'analisi delle serie idrologiche.
No full textIl volume raccoglie i contributi scientifici presentati nel corso della IV Giornata di studio sui "Metodi Statistici e Matematici per l'Analisi delle Serie Idrologiche" svoltasi il 26 maggio 2006 presso l'Università della Tuscia
Metodi statistici e matematici per l'analisi delle serie idrologiche
No full textIl volume raccoglie i contributi scientifici presentati nel corso della III Giornata di studio sui "Metodi Statistici e Matematici per l'Analisi delle Serie Idrologiche" svoltasi il 7 maggio 2004 presso l'Università di Napoli Federico II
On the role of flow forecasts upstream in determining the accuracy of flood forecasting at the basin outlet
No full textThe link between extent of simplification of on-line flood forecasting models and type of adaptive scheme incorporated was investigated. It was used in a model involving on-line flow measurements, carried out at the basin outlet and in an additional position upstream, and combining rainfall-runoff and flood routing procedures. A basic and a modified versions were considered; they substantially stem from the choice of different simplification of basin elements. Namely, in the first version, the parameters are adjusted on-line using the discharges observed at the basin outlet together with those measured at a sub-basin outlet upstream, where flow forecasts are performed through a rainfall-runoff component. In the other version the sub-basin flow forecasts are replaced assuming a persistence of on-line observed discharges. The two model versions were applied to real events observed on large Italian basins. From the analysis of results it appeared that a proper localization of the additional station allowed to obtain an appreciable accuracy of forecasts at the outlet by the basic version and simultaneously made the modified version similar to the basic one. This implies that the raingauge network in the sub-basin may be completely eliminated
Simulazione delle portate dell’Alto Tevere mediante modelli stocastici con suddivisione del bacino
No full textIn questo studio, volto alla previsione delle portate del fiume Tevere a Ponte Nuovo di Torgiano (4147 km2), sono presentate applicazioni della modellistico stocastica multipla basata sull’uso di una serie di ingresso (tipo 1-1), riferita alla precipitazione areale sull’intero bacino, e di più ingressi, relative a 4 regioni in cui è stato suddiviso il bacino stesso. Il comportamento di tali modelli indica la necessità di procedure con una combinazione in cascata di modelli del tipo 1-1, ciascuno riferito ad una zona del bacino. In questo contesto viene quindi discusso un caso di simulazione delle portate nella sezione di S. Lucia (934 km2) e sono indicate alcuni problemi da risolvere nello sviluppo della ricerca, f4ra cui la caratteristica di instabilità della previsione come funzione dell’istante iniziale di preannuncio
A semi-distributed adaptive model for real-time flood forecasting
No full textA semi-distributed model for real-time flood forecasting in large basins is proposed. Variability of rainfall and losses in space is preserved and the effective rainfall-direct runoff model segment based on the Clark procedure is incorporated to rainfall intensity and their evolution in time is represented by the PHI -index; furthermore, an initial period without production of effective rainfall is considered. The first estimation of losses and the associated forecasts of flow are performed at the time corresponding to the first rise observed in the hydrograph. Then the forecasts of flow are corrected at each subsequent time step through the updating of the PHI -index. The model was tested by using rainfall-runoff events observed on two Italian basins and the predictions of flow for lead times up to six hours agree reasonably well with the observations in each event. For example, for the coefficient of persistence, which compares the model forecasts with those generated by the no-model assumption, appreciable positive values were computed. In particular, for the larger basin with an area of 4,147 km2, the mean values were 0.4, 0.4 and 0.5 for forecast lead times of two hours, four hours and six hours, respectively. Good performance of the model is also shown by a comparison of its flow predictions with those derived from a unit hydrograph based model
Structure of a system for on-line flood forecasting
No full textA complete system for real-time flood forecasting in large river basins is presented. It was tested on a large Italian basin with a drainage area of 4147 km2. The experimental network, based on the use of radio waves, involved an ultrasonic sensor for river level measurements and classical instruments for measurements of rainfall and other meteorological quantities. The predictions of flow were carried out by two semi-distributed adaptive models, requiring low computational efforts, for lead-times up to six hours. The system appears to be suitable for operative purposes
A semi-distributed adaptive model for flood forecasting with different representations of losses
No full textThe accuracy of two modified versions of a simple real-time semi-distributed flood forecasting model (RS model) is investigated. These are adaptive rainfall-runoff models obtained from the RS model by modifying the rainfall loss component, which is based on a combination of the runoff coefficient and Φ-index approaches, throughout an ensemble of homogeneous zones into which the basin is sub-divided. Both models assume the total loss of all rainfall in an initial period determined by the two early points of the hydrograph rising limb. The first version (RS1 model) assumes a subsequent constant loss rate while the other (RS2 model) assumes a subsequent loss rate proportional to the rainfall rate.
A comparison of the different models was performed through their application to events observed on two Italian basins. The results revealed a significant sensitivity of flow forecasts to the variations in loss representation, particularly to the selection of the first rainfall producing direct runoff. The RS and RS2 models provided reasonably appropriate flood forecasting for lead times up to 6h
Transients in damaged closed conduits. A tool for leak detection and possible ‘side effects’
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