Dissertations / Theses: 'Costruzioni idrauliche'

1

Bigi, Alessandro <1977&gt. "Un modello spazialmente distribuito per la modellazione fisicamente basata del contributo locale al trasporto solido in sospensione in alvei fluviali." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/490/1/dottorato_bigi.pdf.

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La presente tesi di dottorato si propone lo sviluppo di un modello spazialmente distribuito per produrre una stima dell'erosione superficiale in bacini appenninici. Il modello è stato progettato per simulare in maniera fisicamente basata il distacco di suolo e di sedimento depositato ad opera delle precipitazioni e del deflusso superficiale, e si propone come utile strumento per lo studio della vulnerabilità del territorio collinare e montano. Si è scelto un bacino collinare dell'Appennino bolognese per testare le capacità del modello e verificarne la robustezza. Dopo una breve introduzione per esporre il contesto in cui si opera, nel primo capitolo sono presentate le principali forme di erosione e una loro descrizione fisico-matematica, nel secondo capitolo verranno introdotti i principali prodotti della modellistica di erosione del suolo, spiegando quale interpretazione dei fenomeni fisici è stata data. Nel terzo capitolo verrà descritto il modello oggetto della tesi di dottorando, con una prima breve descrizione della componente afflussi-deflussi ed una seconda descrizione della componente di erosione del suolo. Nel quarto capitolo verrà descritto il bacino di applicazione del modello, i risultati della calibrazione ed un'analisi di sensitività. Infine si presenteranno le conclusioni sullo studio.

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2

Bigi, Alessandro <1977&gt. "Un modello spazialmente distribuito per la modellazione fisicamente basata del contributo locale al trasporto solido in sospensione in alvei fluviali." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/490/.

Full text

Abstract:

La presente tesi di dottorato si propone lo sviluppo di un modello spazialmente distribuito per produrre una stima dell'erosione superficiale in bacini appenninici. Il modello è stato progettato per simulare in maniera fisicamente basata il distacco di suolo e di sedimento depositato ad opera delle precipitazioni e del deflusso superficiale, e si propone come utile strumento per lo studio della vulnerabilità del territorio collinare e montano. Si è scelto un bacino collinare dell'Appennino bolognese per testare le capacità del modello e verificarne la robustezza. Dopo una breve introduzione per esporre il contesto in cui si opera, nel primo capitolo sono presentate le principali forme di erosione e una loro descrizione fisico-matematica, nel secondo capitolo verranno introdotti i principali prodotti della modellistica di erosione del suolo, spiegando quale interpretazione dei fenomeni fisici è stata data. Nel terzo capitolo verrà descritto il modello oggetto della tesi di dottorando, con una prima breve descrizione della componente afflussi-deflussi ed una seconda descrizione della componente di erosione del suolo. Nel quarto capitolo verrà descritto il bacino di applicazione del modello, i risultati della calibrazione ed un'analisi di sensitività. Infine si presenteranno le conclusioni sullo studio.

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3

Casadio, Andrea <1977&gt. "Analisi degli aspetti di qualità nella gestione dei sistemi di drenaggio urbano attraverso modellazione numerica e indagini di campo." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/879/1/Tesi_Casadio_Andrea.pdf.

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In order to protect river water quality, highly affected in urban areas by continuos as intermittent immissions, it is necessary to adopt measures to intercept and treat these polluted flows. In particular during rain events, river water quality is affected by CSOs activation. Built in order to protect the sewer system and the WWTP by increased flows due to heavy rains, CSOs divert excess flows to the receiving water body. On the basis of several scientific papers, and of direct evidences as well, that demonstrate the detrimental effect of CSOs discharges, also the legislative framework moved towards a stream standard point of view. The WFD (EU/69/2000) sets new goals for receiving water quality, and groundwater as well, through an integrated immission/emissions phylosophy, in which emission limits are associated with effluent standards, based on the receiving water characteristics and their specific use. For surface waters the objective is that of a “good” ecological and chemical quality status. A surface water is defined as of good ecological quality if there is only slight departure from the biological community that would be expected in conditions of minimal anthropogenic impact. Each Member State authority is responsible for preparing and implementing a River Basin Management Plan to achieve the good ecological quality, and comply with WFD requirements. In order to cope with WFD targets, and thus to improve urban receiving water quality, a CSOs control strategy need to be implemented. Temporarily storing the overflow (or at least part of it) into tanks and treating it in the WWTP, after the end of the storm, showed good results in reducing total pollutant mass spilled into the receiving river. Italian State Authority, in order to comply with WFD statements, sets general framework, and each Region has to adopt a Water Remediation Plan (PTA, Piano Tutela Acque), setting goals, methods, and terms, to improve river water quality. Emilia Romagna PTA sets 25% reduction up to 2008, and 50% reduction up to 2015 fo total pollutants masses delivered by CSOs spills. In order to plan remediation actions, a deep insight into spills dynamics is thus of great importance. The present thesis tries to understand spills dynamics through a numerical and an experimental approach. A four months monitoring and sampling campaign was set on the Bologna sewer network, and on the Navile Channel, that is the WWTP receiving water , and that receives flows from up to 28 CSOs during rain events. On the other hand, the full model of the sewer network, was build with the commercial software InfoWorks CS. The model was either calibrated with the data from the monitoring and sampling campaign. Through further model simulations interdependencies among masses spilled, rain characteristics and basin characteristics are looked for. The thesis can be seen as a basis for further insighs and for planning remediation actions.

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4

Casadio, Andrea <1977&gt. "Analisi degli aspetti di qualità nella gestione dei sistemi di drenaggio urbano attraverso modellazione numerica e indagini di campo." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/879/.

Full text

Abstract:

In order to protect river water quality, highly affected in urban areas by continuos as intermittent immissions, it is necessary to adopt measures to intercept and treat these polluted flows. In particular during rain events, river water quality is affected by CSOs activation. Built in order to protect the sewer system and the WWTP by increased flows due to heavy rains, CSOs divert excess flows to the receiving water body. On the basis of several scientific papers, and of direct evidences as well, that demonstrate the detrimental effect of CSOs discharges, also the legislative framework moved towards a stream standard point of view. The WFD (EU/69/2000) sets new goals for receiving water quality, and groundwater as well, through an integrated immission/emissions phylosophy, in which emission limits are associated with effluent standards, based on the receiving water characteristics and their specific use. For surface waters the objective is that of a “good” ecological and chemical quality status. A surface water is defined as of good ecological quality if there is only slight departure from the biological community that would be expected in conditions of minimal anthropogenic impact. Each Member State authority is responsible for preparing and implementing a River Basin Management Plan to achieve the good ecological quality, and comply with WFD requirements. In order to cope with WFD targets, and thus to improve urban receiving water quality, a CSOs control strategy need to be implemented. Temporarily storing the overflow (or at least part of it) into tanks and treating it in the WWTP, after the end of the storm, showed good results in reducing total pollutant mass spilled into the receiving river. Italian State Authority, in order to comply with WFD statements, sets general framework, and each Region has to adopt a Water Remediation Plan (PTA, Piano Tutela Acque), setting goals, methods, and terms, to improve river water quality. Emilia Romagna PTA sets 25% reduction up to 2008, and 50% reduction up to 2015 fo total pollutants masses delivered by CSOs spills. In order to plan remediation actions, a deep insight into spills dynamics is thus of great importance. The present thesis tries to understand spills dynamics through a numerical and an experimental approach. A four months monitoring and sampling campaign was set on the Bologna sewer network, and on the Navile Channel, that is the WWTP receiving water , and that receives flows from up to 28 CSOs during rain events. On the other hand, the full model of the sewer network, was build with the commercial software InfoWorks CS. The model was either calibrated with the data from the monitoring and sampling campaign. Through further model simulations interdependencies among masses spilled, rain characteristics and basin characteristics are looked for. The thesis can be seen as a basis for further insighs and for planning remediation actions.

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5

Marchi, Angela <1980&gt. "Ottimizzazione delle reti di distribuzione idrica tramite algoritmi genetici multi-obiettivo." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1381/1/Marchi_Angela_tesi.pdf.

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Water distribution networks optimization is a challenging problem due to the dimension and the complexity of these systems. Since the last half of the twentieth century this field has been investigated by many authors. Recently, to overcome discrete nature of variables and non linearity of equations, the research has been focused on the development of heuristic algorithms. This algorithms do not require continuity and linearity of the problem functions because they are linked to an external hydraulic simulator that solve equations of mass continuity and of energy conservation of the network. In this work, a NSGA-II (Non-dominating Sorting Genetic Algorithm) has been used. This is a heuristic multi-objective genetic algorithm based on the analogy of evolution in nature. Starting from an initial random set of solutions, called population, it evolves them towards a front of solutions that minimize, separately and contemporaneously, all the objectives. This can be very useful in practical problems where multiple and discordant goals are common. Usually, one of the main drawback of these algorithms is related to time consuming: being a stochastic research, a lot of solutions must be analized before good ones are found. Results of this thesis about the classical optimal design problem shows that is possible to improve results modifying the mathematical definition of objective functions and the survival criterion, inserting good solutions created by a Cellular Automata and using rules created by classifier algorithm (C4.5). This part has been tested using the version of NSGA-II supplied by Centre for Water Systems (University of Exeter, UK) in MATLAB® environment. Even if orientating the research can constrain the algorithm with the risk of not finding the optimal set of solutions, it can greatly improve the results. Subsequently, thanks to CINECA help, a version of NSGA-II has been implemented in C language and parallelized: results about the global parallelization show the speed up, while results about the island parallelization show that communication among islands can improve the optimization. Finally, some tests about the optimization of pump scheduling have been carried out. In this case, good results are found for a small network, while the solutions of a big problem are affected by the lack of constraints on the number of pump switches. Possible future research is about the insertion of further constraints and the evolution guide. In the end, the optimization of water distribution systems is still far from a definitive solution, but the improvement in this field can be very useful in reducing the solutions cost of practical problems, where the high number of variables makes their management very difficult from human point of view.

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6

Marchi, Angela <1980&gt. "Ottimizzazione delle reti di distribuzione idrica tramite algoritmi genetici multi-obiettivo." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1381/.

Full text

Abstract:

Water distribution networks optimization is a challenging problem due to the dimension and the complexity of these systems. Since the last half of the twentieth century this field has been investigated by many authors. Recently, to overcome discrete nature of variables and non linearity of equations, the research has been focused on the development of heuristic algorithms. This algorithms do not require continuity and linearity of the problem functions because they are linked to an external hydraulic simulator that solve equations of mass continuity and of energy conservation of the network. In this work, a NSGA-II (Non-dominating Sorting Genetic Algorithm) has been used. This is a heuristic multi-objective genetic algorithm based on the analogy of evolution in nature. Starting from an initial random set of solutions, called population, it evolves them towards a front of solutions that minimize, separately and contemporaneously, all the objectives. This can be very useful in practical problems where multiple and discordant goals are common. Usually, one of the main drawback of these algorithms is related to time consuming: being a stochastic research, a lot of solutions must be analized before good ones are found. Results of this thesis about the classical optimal design problem shows that is possible to improve results modifying the mathematical definition of objective functions and the survival criterion, inserting good solutions created by a Cellular Automata and using rules created by classifier algorithm (C4.5). This part has been tested using the version of NSGA-II supplied by Centre for Water Systems (University of Exeter, UK) in MATLAB® environment. Even if orientating the research can constrain the algorithm with the risk of not finding the optimal set of solutions, it can greatly improve the results. Subsequently, thanks to CINECA help, a version of NSGA-II has been implemented in C language and parallelized: results about the global parallelization show the speed up, while results about the island parallelization show that communication among islands can improve the optimization. Finally, some tests about the optimization of pump scheduling have been carried out. In this case, good results are found for a small network, while the solutions of a big problem are affected by the lack of constraints on the number of pump switches. Possible future research is about the insertion of further constraints and the evolution guide. In the end, the optimization of water distribution systems is still far from a definitive solution, but the improvement in this field can be very useful in reducing the solutions cost of practical problems, where the high number of variables makes their management very difficult from human point of view.

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7

Gottardi, Gianluca <1967&gt. "Dimensionamento di invasi per il controllo dei deflussi nei bacini urbanizzati." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1767/1/Gottardi_Gianluca_Tesi.pdf.

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Urbanization is a continuing phenomenon in all the world. Grasslands, forests, etc. are being continually changed to residential, commercial and industrial complexes, roads and streets, and so on. One of the side effects of urbanization with which engineers and planners must deal with, is the increase of peak flows and volumes of runoff from rainfall events. As a result, the urban drainage and flood control systems must be designed to accommodate the peak flows from a variety of storms that may occur. Usually the peak flow, after development, is required not to exceed what would have occurred from the same storm under conditions existing prior to development. In order to do this it is necessary to design detention storage to hold back runoff and to release it downstream at controlled rates. In the first part of the work have been developed various simplified formulations that can be adopted for the design of stormwater detention facilities. In order to obtain a simplified hydrograph were adopted two approaches: the kinematic routing technique and the linear reservoir schematization. For the two approaches have been also obtained other two formulations depending if the IDF (intensity-duration-frequency) curve is described with two or three parameters. Other formulations have been developed taking into account if the outlet have a constant discharge or it depends on the water level in the pond. All these formulations can be easily applied when are known the characteristics of the drainage system and maximum discharge that these is in the outlet and has been defined a Return Period which characterize the IDF curve. In this way the volume of the detention pond can be calculated. In the second part of the work have been analyzed the design of detention ponds adopting continuous simulation models. The drainage systems adopted for the simulations, performed with SWMM5, are fictitious systems characterized by different sizes, and different shapes of the catchments and with a rainfall historical time series of 16 years recorded in Bologna. This approach suffers from the fact that continuous record of rainfall is often not available and when it is, the cost of such modelling can be very expensive, and that the majority of design practitioners are not prepared to use continuous long term modelling in the design of stormwater detention facilities. In the third part of the work have been analyzed statistical and stochastic methodologies in order to define the volume of the detention pond. In particular have been adopted the results of the long term simulation, performed with SWMM, to obtain the data to apply statistic and stochastic formulation. All these methodologies have been compared and correction coefficient have been proposed on the basis of the statistic and stochastic form. In this way engineers which have to design a detention pond can apply a simplified procedure appropriately corrected with the proposed coefficient.

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8

Gottardi, Gianluca <1967&gt. "Dimensionamento di invasi per il controllo dei deflussi nei bacini urbanizzati." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1767/.

Full text

Abstract:

Urbanization is a continuing phenomenon in all the world. Grasslands, forests, etc. are being continually changed to residential, commercial and industrial complexes, roads and streets, and so on. One of the side effects of urbanization with which engineers and planners must deal with, is the increase of peak flows and volumes of runoff from rainfall events. As a result, the urban drainage and flood control systems must be designed to accommodate the peak flows from a variety of storms that may occur. Usually the peak flow, after development, is required not to exceed what would have occurred from the same storm under conditions existing prior to development. In order to do this it is necessary to design detention storage to hold back runoff and to release it downstream at controlled rates. In the first part of the work have been developed various simplified formulations that can be adopted for the design of stormwater detention facilities. In order to obtain a simplified hydrograph were adopted two approaches: the kinematic routing technique and the linear reservoir schematization. For the two approaches have been also obtained other two formulations depending if the IDF (intensity-duration-frequency) curve is described with two or three parameters. Other formulations have been developed taking into account if the outlet have a constant discharge or it depends on the water level in the pond. All these formulations can be easily applied when are known the characteristics of the drainage system and maximum discharge that these is in the outlet and has been defined a Return Period which characterize the IDF curve. In this way the volume of the detention pond can be calculated. In the second part of the work have been analyzed the design of detention ponds adopting continuous simulation models. The drainage systems adopted for the simulations, performed with SWMM5, are fictitious systems characterized by different sizes, and different shapes of the catchments and with a rainfall historical time series of 16 years recorded in Bologna. This approach suffers from the fact that continuous record of rainfall is often not available and when it is, the cost of such modelling can be very expensive, and that the majority of design practitioners are not prepared to use continuous long term modelling in the design of stormwater detention facilities. In the third part of the work have been analyzed statistical and stochastic methodologies in order to define the volume of the detention pond. In particular have been adopted the results of the long term simulation, performed with SWMM, to obtain the data to apply statistic and stochastic formulation. All these methodologies have been compared and correction coefficient have been proposed on the basis of the statistic and stochastic form. In this way engineers which have to design a detention pond can apply a simplified procedure appropriately corrected with the proposed coefficient.

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9

Lenzi, Chiara <1974&gt. "Efficienza energetica dei sistemi acquedottistici: ruolo delle perdite idriche." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2874/1/lenzi_chiara_tesi.pdf.

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Il lavoro di ricerca esplora il panorama dell’efficienza energetica dei sistemi acquedottistici, soffermandosi a considerare possibili indicatori che possano valutarla in maniera corretta e completa, in particolare nei confronti della presenza di perdite in rete. Si prendono in considerazione con maggiore attenzione, tra tutte le strategie per aumentare l’efficienza energetica, quelle che contemporaneamente producono anche risparmi idrici, come la riduzione della pressione e la ricerca attiva delle perdite . Dopo un inquadramento internazionale, sono stati analizzati mediante mappe tematiche di intensità energetica, i consumi energetici specifici sui sistemi acquedottistici della regione Emilia Romagna per gli anni 2006 e 2007, si è passati ad una analisi critica degli indicatori attualmente in uso. Inoltre per casi di studio sintetici e tutti i casi di studio proposti, si sono valutate curve di relazione tra percentuale di perdita idrica e aumento del consumo energetico, in grado di dare indicazioni su come ciascun sistema reagisce, in termini di aumento dell’energia consumata, all’aumentare del livello di perdita. Questa relazione appare fortemente influenzata da fattori come la modalità di pompaggio, la posizione delle rotture sulla rete e la scabrezza delle condotte. E’ emersa la necessità solo poter analizzare separatamentel’influenza sull’efficienza energeticadei sistemi di pompaggio e della rete, mostrando il ruolo importante con cui questa contribuisce all’efficienza globale del sistema. Viene proposto uno sviluppo ulteriore dell’indicatore GEE Global Energy Efficiency (Abadia, 2008), che consente di distinguere l’impatto sull’efficienza energetica dovuto alle perdite idriche e alla struttura intrinseca della rete, in termini di collocazione reciproca tra risorsa idrica e domanda e schema impiantistico.Questa metodologia di analisi dell’efficienza energetica è stata applicata ai casi di studio, sia sintetici che reali, il distretto di Marzaglia (MO) e quello di Mirabello (FE), entrambi alimentati da pompe a giri variabili.. La ricerca ha consentito di mostrare inoltre il ruolo della modellazione numerica in particolare nell’analisi dell’effetto prodotto sull’efficienza energetica dalla presenza di perdite idriche. Nell’ultimo capitolo si completa la panoramica dei benefici ottenibili attraverso la riduzione della pressione, che nei casi citati viene conseguita tramite pompe asservite ad inverter, con il caso di studio del distretto Bolognina all’interno del sistema di distribuzione di Bologna, che vede l’utilizzo di valvole riduttrici di pressione. Oltre a stimare il risparmio energetico derivante dalla riduzione delle perdite ottenuta tramite le PRV, sono stati valutati su modello i benefici energetici conseguenti all’introduzione nel distretto di turbine per la produzione di energia

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10

Lenzi, Chiara <1974&gt. "Efficienza energetica dei sistemi acquedottistici: ruolo delle perdite idriche." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2874/.

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Abstract:

Il lavoro di ricerca esplora il panorama dell’efficienza energetica dei sistemi acquedottistici, soffermandosi a considerare possibili indicatori che possano valutarla in maniera corretta e completa, in particolare nei confronti della presenza di perdite in rete. Si prendono in considerazione con maggiore attenzione, tra tutte le strategie per aumentare l’efficienza energetica, quelle che contemporaneamente producono anche risparmi idrici, come la riduzione della pressione e la ricerca attiva delle perdite . Dopo un inquadramento internazionale, sono stati analizzati mediante mappe tematiche di intensità energetica, i consumi energetici specifici sui sistemi acquedottistici della regione Emilia Romagna per gli anni 2006 e 2007, si è passati ad una analisi critica degli indicatori attualmente in uso. Inoltre per casi di studio sintetici e tutti i casi di studio proposti, si sono valutate curve di relazione tra percentuale di perdita idrica e aumento del consumo energetico, in grado di dare indicazioni su come ciascun sistema reagisce, in termini di aumento dell’energia consumata, all’aumentare del livello di perdita. Questa relazione appare fortemente influenzata da fattori come la modalità di pompaggio, la posizione delle rotture sulla rete e la scabrezza delle condotte. E’ emersa la necessità solo poter analizzare separatamentel’influenza sull’efficienza energeticadei sistemi di pompaggio e della rete, mostrando il ruolo importante con cui questa contribuisce all’efficienza globale del sistema. Viene proposto uno sviluppo ulteriore dell’indicatore GEE Global Energy Efficiency (Abadia, 2008), che consente di distinguere l’impatto sull’efficienza energetica dovuto alle perdite idriche e alla struttura intrinseca della rete, in termini di collocazione reciproca tra risorsa idrica e domanda e schema impiantistico.Questa metodologia di analisi dell’efficienza energetica è stata applicata ai casi di studio, sia sintetici che reali, il distretto di Marzaglia (MO) e quello di Mirabello (FE), entrambi alimentati da pompe a giri variabili.. La ricerca ha consentito di mostrare inoltre il ruolo della modellazione numerica in particolare nell’analisi dell’effetto prodotto sull’efficienza energetica dalla presenza di perdite idriche. Nell’ultimo capitolo si completa la panoramica dei benefici ottenibili attraverso la riduzione della pressione, che nei casi citati viene conseguita tramite pompe asservite ad inverter, con il caso di studio del distretto Bolognina all’interno del sistema di distribuzione di Bologna, che vede l’utilizzo di valvole riduttrici di pressione. Oltre a stimare il risparmio energetico derivante dalla riduzione delle perdite ottenuta tramite le PRV, sono stati valutati su modello i benefici energetici conseguenti all’introduzione nel distretto di turbine per la produzione di energia

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11

Castiglioni, Simone <1981&gt. "Modelli per la stima delle risorse idriche superficiali in bacini idrografici non strumentati." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2992/1/castiglioni_simone_tesi.pdf.

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12

Castiglioni, Simone <1981&gt. "Modelli per la stima delle risorse idriche superficiali in bacini idrografici non strumentati." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2992/.

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13

Lombardi, Laura <1975&gt. "Calibrazione di modelli idrologici con algoritmi multiobiettivo." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3386/1/lombardi_laura_tesi.pdf.

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Traditional procedures for rainfall-runoff model calibration are generally based on the fit of the individual values of simulated and observed hydrographs. It is used here an alternative option that is carried out by matching, in the optimisation process, a set of statistics of the river flow. Such approach has the additional, significant advantage to allow also a straightforward regional calibration of the model parameters, based on the regionalisation of the selected statistics. The minimisation of the set of objective functions is carried out by using the AMALGAM algorithm, leading to the identification of behavioural parameter sets. The procedure is applied to a set of river basins located in central Italy: the basins are treated alternatively as gauged and ungauged and, as a term of comparison, the results obtained with a traditional time-domain calibration is also presented. The results show that a suitable choice of the statistics to be optimised leads to interesting results in real world case studies as far as the reproduction of the different flow regimes is concerned.

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14

Lombardi, Laura <1975&gt. "Calibrazione di modelli idrologici con algoritmi multiobiettivo." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3386/.

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Abstract:

Traditional procedures for rainfall-runoff model calibration are generally based on the fit of the individual values of simulated and observed hydrographs. It is used here an alternative option that is carried out by matching, in the optimisation process, a set of statistics of the river flow. Such approach has the additional, significant advantage to allow also a straightforward regional calibration of the model parameters, based on the regionalisation of the selected statistics. The minimisation of the set of objective functions is carried out by using the AMALGAM algorithm, leading to the identification of behavioural parameter sets. The procedure is applied to a set of river basins located in central Italy: the basins are treated alternatively as gauged and ungauged and, as a term of comparison, the results obtained with a traditional time-domain calibration is also presented. The results show that a suitable choice of the statistics to be optimised leads to interesting results in real world case studies as far as the reproduction of the different flow regimes is concerned.

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15

Coccia, Gabriele <1983&gt. "Analysis and developments of uncertainty processors for real time flood forecasting." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3423/1/Tesi.pdf.

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Abstract:

The hydrologic risk (and the hydro-geologic one, closely related to it) is, and has always been, a very relevant issue, due to the severe consequences that may be provoked by a flooding or by waters in general in terms of human and economic losses. Floods are natural phenomena, often catastrophic, and cannot be avoided, but their damages can be reduced if they are predicted sufficiently in advance. For this reason, the flood forecasting plays an essential role in the hydro-geological and hydrological risk prevention. Thanks to the development of sophisticated meteorological, hydrologic and hydraulic models, in recent decades the flood forecasting has made a significant progress, nonetheless, models are imperfect, which means that we are still left with a residual uncertainty on what will actually happen. In this thesis, this type of uncertainty is what will be discussed and analyzed. In operational problems, it is possible to affirm that the ultimate aim of forecasting systems is not to reproduce the river behavior, but this is only a means through which reducing the uncertainty associated to what will happen as a consequence of a precipitation event. In other words, the main objective is to assess whether or not preventive interventions should be adopted and which operational strategy may represent the best option. The main problem for a decision maker is to interpret model results and translate them into an effective intervention strategy. To make this possible, it is necessary to clearly define what is meant by uncertainty, since in the literature confusion is often made on this issue. Therefore, the first objective of this thesis is to clarify this concept, starting with a key question: should be the choice of the intervention strategy to adopt based on the evaluation of the model prediction based on its ability to represent the reality or on the evaluation of what actually will happen on the basis of the information given by the model forecast? Once the previous idea is made unambiguous, the other main concern of this work is to develope a tool that can provide an effective decision support, making possible doing objective and realistic risk evaluations. In particular, such tool should be able to provide an uncertainty assessment as accurate as possible. This means primarily three things: it must be able to correctly combine all the available deterministic forecasts, it must assess the probability distribution of the predicted quantity and it must quantify the flooding probability. Furthermore, given that the time to implement prevention strategies is often limited, the flooding probability will have to be linked to the time of occurrence. For this reason, it is necessary to quantify the flooding probability within a horizon time related to that required to implement the intervention strategy and it is also necessary to assess the probability of the flooding time.

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16

Coccia, Gabriele <1983&gt. "Analysis and developments of uncertainty processors for real time flood forecasting." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3423/.

Full text

Abstract:

The hydrologic risk (and the hydro-geologic one, closely related to it) is, and has always been, a very relevant issue, due to the severe consequences that may be provoked by a flooding or by waters in general in terms of human and economic losses. Floods are natural phenomena, often catastrophic, and cannot be avoided, but their damages can be reduced if they are predicted sufficiently in advance. For this reason, the flood forecasting plays an essential role in the hydro-geological and hydrological risk prevention. Thanks to the development of sophisticated meteorological, hydrologic and hydraulic models, in recent decades the flood forecasting has made a significant progress, nonetheless, models are imperfect, which means that we are still left with a residual uncertainty on what will actually happen. In this thesis, this type of uncertainty is what will be discussed and analyzed. In operational problems, it is possible to affirm that the ultimate aim of forecasting systems is not to reproduce the river behavior, but this is only a means through which reducing the uncertainty associated to what will happen as a consequence of a precipitation event. In other words, the main objective is to assess whether or not preventive interventions should be adopted and which operational strategy may represent the best option. The main problem for a decision maker is to interpret model results and translate them into an effective intervention strategy. To make this possible, it is necessary to clearly define what is meant by uncertainty, since in the literature confusion is often made on this issue. Therefore, the first objective of this thesis is to clarify this concept, starting with a key question: should be the choice of the intervention strategy to adopt based on the evaluation of the model prediction based on its ability to represent the reality or on the evaluation of what actually will happen on the basis of the information given by the model forecast? Once the previous idea is made unambiguous, the other main concern of this work is to develope a tool that can provide an effective decision support, making possible doing objective and realistic risk evaluations. In particular, such tool should be able to provide an uncertainty assessment as accurate as possible. This means primarily three things: it must be able to correctly combine all the available deterministic forecasts, it must assess the probability distribution of the predicted quantity and it must quantify the flooding probability. Furthermore, given that the time to implement prevention strategies is often limited, the flooding probability will have to be linked to the time of occurrence. For this reason, it is necessary to quantify the flooding probability within a horizon time related to that required to implement the intervention strategy and it is also necessary to assess the probability of the flooding time.

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17

Ciccarello, Annalisa <1982&gt. "Experimental and numerical analyses about the efficiency of flow through devices for the sediment controll in urban runoff." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3959/1/Tesi_tot.pdf.

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Abstract:

As land is developed, the impervious surfaces that are created increase the amount of runoff during rainfall events, disrupting the natural hydrologic cycle, with an increment in volume of runoff and in pollutant loadings. Pollutants deposited or derived from an activity on the land surface will likely end up in stormwater runoff in some concentration, such as nutrients, sediment, heavy metals, hydrocarbons, gasoline additives, pathogens, deicers, herbicides and pesticides. Several of these pollutants are particulate-bound, so it appears clear that sediment removal can provide significant water-quality improvements and it appears to be important the knowledge of the ability of stromwater treatment devices to retain particulate matter. For this reason three different units which remove sediments have been tested through laboratory. In particular a roadside gully pot has been tested under steady hydraulic conditions, varying the characteristics of the influent solids (diameter, particle size distribution and specific gravity). The efficiency in terms of particles retained has been evaluated as a function of influent flow rate and particles characteristics; results have been compared to efficiency evaluated applying an overflow rate model. Furthermore the role of particles settling velocity in efficiency determination has been investigated. After the experimental runs on the gully pot, a standard full-scale model of an hydrodynamic separator (HS) has been tested under unsteady influent flow rate condition, and constant solid concentration at the input. The results presented in this study illustrate that particle separation efficiency of the unit is predominately influenced by operating flow rate, which strongly affects the particles and hydraulic residence time of the system. The efficiency data have been compared to results obtained from a modified overflow rate model; moreover the residence time distribution has been experimentally determined through tracer analyses for several steady flow rates. Finally three testing experiments have been performed for two different configurations of a full-scale model of a clarifier (linear and crenulated) under unsteady influent flow rate condition, and constant solid concentration at the input. The results illustrate that particle separation efficiency of the unit is predominately influenced by the configuration of the unit itself. Turbidity measures have been used to compare turbidity with the suspended sediments concentration, in order to find a correlation between these two values, which can allow to have a measure of the sediments concentration simply installing a turbidity probe.

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18

Ciccarello, Annalisa <1982&gt. "Experimental and numerical analyses about the efficiency of flow through devices for the sediment controll in urban runoff." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3959/.

Full text

Abstract:

As land is developed, the impervious surfaces that are created increase the amount of runoff during rainfall events, disrupting the natural hydrologic cycle, with an increment in volume of runoff and in pollutant loadings. Pollutants deposited or derived from an activity on the land surface will likely end up in stormwater runoff in some concentration, such as nutrients, sediment, heavy metals, hydrocarbons, gasoline additives, pathogens, deicers, herbicides and pesticides. Several of these pollutants are particulate-bound, so it appears clear that sediment removal can provide significant water-quality improvements and it appears to be important the knowledge of the ability of stromwater treatment devices to retain particulate matter. For this reason three different units which remove sediments have been tested through laboratory. In particular a roadside gully pot has been tested under steady hydraulic conditions, varying the characteristics of the influent solids (diameter, particle size distribution and specific gravity). The efficiency in terms of particles retained has been evaluated as a function of influent flow rate and particles characteristics; results have been compared to efficiency evaluated applying an overflow rate model. Furthermore the role of particles settling velocity in efficiency determination has been investigated. After the experimental runs on the gully pot, a standard full-scale model of an hydrodynamic separator (HS) has been tested under unsteady influent flow rate condition, and constant solid concentration at the input. The results presented in this study illustrate that particle separation efficiency of the unit is predominately influenced by operating flow rate, which strongly affects the particles and hydraulic residence time of the system. The efficiency data have been compared to results obtained from a modified overflow rate model; moreover the residence time distribution has been experimentally determined through tracer analyses for several steady flow rates. Finally three testing experiments have been performed for two different configurations of a full-scale model of a clarifier (linear and crenulated) under unsteady influent flow rate condition, and constant solid concentration at the input. The results illustrate that particle separation efficiency of the unit is predominately influenced by the configuration of the unit itself. Turbidity measures have been used to compare turbidity with the suspended sediments concentration, in order to find a correlation between these two values, which can allow to have a measure of the sediments concentration simply installing a turbidity probe.

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19

Dottori, Francesco <1980&gt. "Development of parallelizable flood inundation models for large scale analysis." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4635/1/thesis.pdf.

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Abstract:

Flood disasters are a major cause of fatalities and economic losses, and several studies indicate that global flood risk is currently increasing. In order to reduce and mitigate the impact of river flood disasters, the current trend is to integrate existing structural defences with non structural measures. This calls for a wider application of advanced hydraulic models for flood hazard and risk mapping, engineering design, and flood forecasting systems. Within this framework, two different hydraulic models for large scale analysis of flood events have been developed. The two models, named CA2D and IFD-GGA, adopt an integrated approach based on the diffusive shallow water equations and a simplified finite volume scheme. The models are also designed for massive code parallelization, which has a key importance in reducing run times in large scale and high-detail applications. The two models were first applied to several numerical cases, to test the reliability and accuracy of different model versions. Then, the most effective versions were applied to different real flood events and flood scenarios. The IFD-GGA model showed serious problems that prevented further applications. On the contrary, the CA2D model proved to be fast and robust, and able to reproduce 1D and 2D flow processes in terms of water depth and velocity. In most applications the accuracy of model results was good and adequate to large scale analysis. Where complex flow processes occurred local errors were observed, due to the model approximations. However, they did not compromise the correct representation of overall flow processes. In conclusion, the CA model can be a valuable tool for the simulation of a wide range of flood event types, including lowland and flash flood events.

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20

Dottori, Francesco <1980&gt. "Development of parallelizable flood inundation models for large scale analysis." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4635/.

Full text

Abstract:

Flood disasters are a major cause of fatalities and economic losses, and several studies indicate that global flood risk is currently increasing. In order to reduce and mitigate the impact of river flood disasters, the current trend is to integrate existing structural defences with non structural measures. This calls for a wider application of advanced hydraulic models for flood hazard and risk mapping, engineering design, and flood forecasting systems. Within this framework, two different hydraulic models for large scale analysis of flood events have been developed. The two models, named CA2D and IFD-GGA, adopt an integrated approach based on the diffusive shallow water equations and a simplified finite volume scheme. The models are also designed for massive code parallelization, which has a key importance in reducing run times in large scale and high-detail applications. The two models were first applied to several numerical cases, to test the reliability and accuracy of different model versions. Then, the most effective versions were applied to different real flood events and flood scenarios. The IFD-GGA model showed serious problems that prevented further applications. On the contrary, the CA2D model proved to be fast and robust, and able to reproduce 1D and 2D flow processes in terms of water depth and velocity. In most applications the accuracy of model results was good and adequate to large scale analysis. Where complex flow processes occurred local errors were observed, due to the model approximations. However, they did not compromise the correct representation of overall flow processes. In conclusion, the CA model can be a valuable tool for the simulation of a wide range of flood event types, including lowland and flash flood events.

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21

Polyzoni, Chrysanthi <1983&gt. "Lifelines in case of Natural Disaster Emergencies." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4666/1/polyzoni_chrysanthi_tesi.pdf.

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Abstract:

In order to handle Natural disasters, emergency areas are often individuated over the territory, close to populated centres. In these areas, rescue services are located which respond with resources and materials for population relief. A method of automatic positioning of these centres in case of a flood or an earthquake is presented. The positioning procedure consists of two distinct parts developed by the research group of Prof Michael G. H. Bell of Imperial College, London, refined and applied to real cases at the University of Bologna under the coordination of Prof Ezio Todini. There are certain requirements that need to be observed such as the maximum number of rescue points as well as the number of people involved. Initially, the candidate points are decided according to the ones proposed by the local civil protection services. We then calculate all possible routes from each candidate rescue point to all other points, generally using the concept of the "hyperpath", namely a set of paths each one of which may be optimal. The attributes of the road network are of fundamental importance, both for the calculation of the ideal distance and eventual delays due to the event measured in travel time units. In a second phase, the distances are used to decide the optimum rescue point positions using heuristics. This second part functions by "elimination". In the beginning, all points are considered rescue centres. During every interaction we wish to delete one point and calculate the impact it creates. In each case, we delete the point that creates less impact until we reach the number of rescue centres we wish to keep.

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22

Polyzoni, Chrysanthi <1983&gt. "Lifelines in case of Natural Disaster Emergencies." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4666/.

Full text

Abstract:

In order to handle Natural disasters, emergency areas are often individuated over the territory, close to populated centres. In these areas, rescue services are located which respond with resources and materials for population relief. A method of automatic positioning of these centres in case of a flood or an earthquake is presented. The positioning procedure consists of two distinct parts developed by the research group of Prof Michael G. H. Bell of Imperial College, London, refined and applied to real cases at the University of Bologna under the coordination of Prof Ezio Todini. There are certain requirements that need to be observed such as the maximum number of rescue points as well as the number of people involved. Initially, the candidate points are decided according to the ones proposed by the local civil protection services. We then calculate all possible routes from each candidate rescue point to all other points, generally using the concept of the "hyperpath", namely a set of paths each one of which may be optimal. The attributes of the road network are of fundamental importance, both for the calculation of the ideal distance and eventual delays due to the event measured in travel time units. In a second phase, the distances are used to decide the optimum rescue point positions using heuristics. This second part functions by "elimination". In the beginning, all points are considered rescue centres. During every interaction we wish to delete one point and calculate the impact it creates. In each case, we delete the point that creates less impact until we reach the number of rescue centres we wish to keep.

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23

Domeneghetti, Alessio <1981&gt. "Modellistica Idraulico-Matematica per la definizione di strategie di mitigazione del rischio alluvionale." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4900/1/Domeneghetti_Alessio-Tesi.pdf.

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Abstract:

La Comunità Europea, alla luce dei recenti eventi alluvionali occorsi nei Paesi Membri ed al progressivo aumento dei danni economici da essi provocati, ha recentemente emanato una direttiva (Direttiva Europea 2007/60/CE, Flood Directive) per la valutazione e la predisposizione di piani di gestione del rischio idraulico alluvionale. Con riferimento a tale contesto l’attività di ricerca condotta si è concentrata sulla valutazione delle potenzialità offerte dalla modellistica numerico-idraulica mono e bidimensionale quale strumento per l’attuazione della Direttiva 2007/60. Le attività sono state affrontate ponendo particolare attenzione alla valutazione dei termini di incertezza che caratterizzano l’applicazione dei modelli numerico-idraulici, esaminando i possibili effetti di tale incertezza sulla mappatura della pericolosità idraulica. In particolare, lo studio si concentra su diversi tratti fluviali del corso medio inferiore del Fiume Po e si articola in tre parti: 1) analisi dell’incertezza connessa alla definizione delle scale di deflusso in una generica sezione fluviale e valutazione dei suoi effetti sulla calibrazione dei modelli numerici quasi-bidimensionali (quasi-2D); 2) definizione di mappe probabilistiche di allagamento per tratti fluviali arginati in presenza di tre sorgenti di incertezza: incertezza nelle condizioni al contorno di monte, nelle condizioni di valle e nell’identificazione delle eventuali brecce arginali; 3) valutazione dell’applicabilità di un modello quasi-2D per la definizione, a grande scala spaziale, di strategie alternative al tradizionale rialzo dei manufatti arginali per la mitigazione del rischio alluvionale associato a eventi di piena catastrofici. Le analisi condotte, oltre ad aver definito e valutato le potenzialità di metodologie e modelli idraulici a diversa complessità, hanno evidenziato l’entità e l’impatto dei più importanti elementi d’incertezza, sottolineando come la corretta mappatura della pericolosità idraulica debba sempre essere accompagnata da una valutazione della sua incertezza.
In the light of recent catastrophic flood events and the steadily increase of economic losses associated with inundations in Europe, the European Community recently issued the Flood Directive (2007/60/EC), which requires Member States to evaluate and map flood-risk and to develop flood risk management plans. Concerning these issues, the present dissertation focuses on the development and testing of mono and quasi two-dimensional (quasi-2D) numerical hydraulic models for the implementation of Directive 2007/60. The activities are carried out paying particular attention on the evaluation of the main sources of uncertainty that characterize the application of numerical models, examining their possible effect on the flood hazard mapping. The study considers various river branches of the River Po and is structured into three main parts: 1) analysis of rating-curve uncertainty in a given river section and evaluation of its effects on the calibration of roughness coefficients for a quasi-2D, 2) flood hazard mapping for a diked river reach considering three major sources of uncertainties: uncertainties in upstream and downstream boundary conditions and uncertainties in the dike-failure location and breach morphology; 3) development and testing of a quasi-2D hydraulic model to support the large-scale identification of optimal flood-risk mitigation strategies relative to the 500-year flood. The analysis assesses the potential of methodologies and numerical-hydraulic models for flood hazard mapping and highlights the impact of the most important elements of uncertainty, pointing out how a correct flood hazard map should always be accompanied by a throughout uncertainty assessment.

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24

Domeneghetti, Alessio <1981&gt. "Modellistica Idraulico-Matematica per la definizione di strategie di mitigazione del rischio alluvionale." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4900/.

Full text

Abstract:

La Comunità Europea, alla luce dei recenti eventi alluvionali occorsi nei Paesi Membri ed al progressivo aumento dei danni economici da essi provocati, ha recentemente emanato una direttiva (Direttiva Europea 2007/60/CE, Flood Directive) per la valutazione e la predisposizione di piani di gestione del rischio idraulico alluvionale. Con riferimento a tale contesto l’attività di ricerca condotta si è concentrata sulla valutazione delle potenzialità offerte dalla modellistica numerico-idraulica mono e bidimensionale quale strumento per l’attuazione della Direttiva 2007/60. Le attività sono state affrontate ponendo particolare attenzione alla valutazione dei termini di incertezza che caratterizzano l’applicazione dei modelli numerico-idraulici, esaminando i possibili effetti di tale incertezza sulla mappatura della pericolosità idraulica. In particolare, lo studio si concentra su diversi tratti fluviali del corso medio inferiore del Fiume Po e si articola in tre parti: 1) analisi dell’incertezza connessa alla definizione delle scale di deflusso in una generica sezione fluviale e valutazione dei suoi effetti sulla calibrazione dei modelli numerici quasi-bidimensionali (quasi-2D); 2) definizione di mappe probabilistiche di allagamento per tratti fluviali arginati in presenza di tre sorgenti di incertezza: incertezza nelle condizioni al contorno di monte, nelle condizioni di valle e nell’identificazione delle eventuali brecce arginali; 3) valutazione dell’applicabilità di un modello quasi-2D per la definizione, a grande scala spaziale, di strategie alternative al tradizionale rialzo dei manufatti arginali per la mitigazione del rischio alluvionale associato a eventi di piena catastrofici. Le analisi condotte, oltre ad aver definito e valutato le potenzialità di metodologie e modelli idraulici a diversa complessità, hanno evidenziato l’entità e l’impatto dei più importanti elementi d’incertezza, sottolineando come la corretta mappatura della pericolosità idraulica debba sempre essere accompagnata da una valutazione della sua incertezza.
In the light of recent catastrophic flood events and the steadily increase of economic losses associated with inundations in Europe, the European Community recently issued the Flood Directive (2007/60/EC), which requires Member States to evaluate and map flood-risk and to develop flood risk management plans. Concerning these issues, the present dissertation focuses on the development and testing of mono and quasi two-dimensional (quasi-2D) numerical hydraulic models for the implementation of Directive 2007/60. The activities are carried out paying particular attention on the evaluation of the main sources of uncertainty that characterize the application of numerical models, examining their possible effect on the flood hazard mapping. The study considers various river branches of the River Po and is structured into three main parts: 1) analysis of rating-curve uncertainty in a given river section and evaluation of its effects on the calibration of roughness coefficients for a quasi-2D, 2) flood hazard mapping for a diked river reach considering three major sources of uncertainties: uncertainties in upstream and downstream boundary conditions and uncertainties in the dike-failure location and breach morphology; 3) development and testing of a quasi-2D hydraulic model to support the large-scale identification of optimal flood-risk mitigation strategies relative to the 500-year flood. The analysis assesses the potential of methodologies and numerical-hydraulic models for flood hazard mapping and highlights the impact of the most important elements of uncertainty, pointing out how a correct flood hazard map should always be accompanied by a throughout uncertainty assessment.

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25

Montosi, Elena <1981&gt. "Variabilità spaziale dei parametri di modelli afflussi-deflussi." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4905/1/Montosi_Elena_tesi.pdf.

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Abstract:

L’invarianza spaziale dei parametri di un modello afflussi-deflussi può rivelarsi una soluzione pratica e valida nel caso si voglia stimare la disponibilità di risorsa idrica di un’area. La simulazione idrologica è infatti uno strumento molto adottato ma presenta alcune criticità legate soprattutto alla necessità di calibrare i parametri del modello. Se si opta per l’applicazione di modelli spazialmente distribuiti, utili perché in grado di rendere conto della variabilità spaziale dei fenomeni che concorrono alla formazione di deflusso, il problema è solitamente legato all’alto numero di parametri in gioco. Assumendo che alcuni di questi siano omogenei nello spazio, dunque presentino lo stesso valore sui diversi bacini, è possibile ridurre il numero complessivo dei parametri che necessitano della calibrazione. Si verifica su base statistica questa assunzione, ricorrendo alla stima dell’incertezza parametrica valutata per mezzo di un algoritmo MCMC. Si nota che le distribuzioni dei parametri risultano in diversa misura compatibili sui bacini considerati. Quando poi l’obiettivo è la stima della disponibilità di risorsa idrica di bacini non strumentati, l’ipotesi di invarianza dei parametri assume ancora più importanza; solitamente infatti si affronta questo problema ricorrendo a lunghe analisi di regionalizzazione dei parametri. In questa sede invece si propone una procedura di cross-calibrazione che viene realizzata adottando le informazioni provenienti dai bacini strumentati più simili al sito di interesse. Si vuole raggiungere cioè un giusto compromesso tra lo svantaggio derivante dall’assumere i parametri del modello costanti sui bacini strumentati e il beneficio legato all’introduzione, passo dopo passo, di nuove e importanti informazioni derivanti dai bacini strumentati coinvolti nell’analisi. I risultati dimostrano l’utilità della metodologia proposta; si vede infatti che, in fase di validazione sul bacino considerato non strumentato, è possibile raggiungere un buona concordanza tra le serie di portata simulate e osservate.
Spatial homogeneity of rainfall-runoff model parameters can be a practical and valuable solution in order to assess water availability of a region. Hydrological simulation is indeed an handy tool but it is critical as it usually requires some degree of calibration. Calibration of spatially distributed models, that are particularly useful to describe the variability of physical processes that play a role in runoff generation, is challenging because of the high number of involved parameters. But some parameters can be homogeneous in space, therefore allowing one to reduce their total amount when multiple basins are considered. This assumption is verified on a statistical ground, making use of an MCMC algorithm to assess the parameter uncertainty; as a result the parameter distributions are with varying degrees comparable on the different catchments. When one wants to simulate the hydrological response of ungauged catchments, the hypothesis of spatial homogeneity of parameters has even more relevance; a long regionalization technique is usually applied, but we propose a cross-calibration procedure to be used at regional level. With this procedure model parameters are calibrated making use of hydrological information coming from gauged basins that are more similar to the site of interest. We want to analyze the trade-off between assuming the parameters homogeneous in space and adding new information as the cross-calibration evolves. Results show that the cross-calibration is a process well worth using; in validation in fact a good agreement is reached between observed and simulated discharges.

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26

Montosi, Elena <1981&gt. "Variabilità spaziale dei parametri di modelli afflussi-deflussi." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4905/.

Full text

Abstract:

L’invarianza spaziale dei parametri di un modello afflussi-deflussi può rivelarsi una soluzione pratica e valida nel caso si voglia stimare la disponibilità di risorsa idrica di un’area. La simulazione idrologica è infatti uno strumento molto adottato ma presenta alcune criticità legate soprattutto alla necessità di calibrare i parametri del modello. Se si opta per l’applicazione di modelli spazialmente distribuiti, utili perché in grado di rendere conto della variabilità spaziale dei fenomeni che concorrono alla formazione di deflusso, il problema è solitamente legato all’alto numero di parametri in gioco. Assumendo che alcuni di questi siano omogenei nello spazio, dunque presentino lo stesso valore sui diversi bacini, è possibile ridurre il numero complessivo dei parametri che necessitano della calibrazione. Si verifica su base statistica questa assunzione, ricorrendo alla stima dell’incertezza parametrica valutata per mezzo di un algoritmo MCMC. Si nota che le distribuzioni dei parametri risultano in diversa misura compatibili sui bacini considerati. Quando poi l’obiettivo è la stima della disponibilità di risorsa idrica di bacini non strumentati, l’ipotesi di invarianza dei parametri assume ancora più importanza; solitamente infatti si affronta questo problema ricorrendo a lunghe analisi di regionalizzazione dei parametri. In questa sede invece si propone una procedura di cross-calibrazione che viene realizzata adottando le informazioni provenienti dai bacini strumentati più simili al sito di interesse. Si vuole raggiungere cioè un giusto compromesso tra lo svantaggio derivante dall’assumere i parametri del modello costanti sui bacini strumentati e il beneficio legato all’introduzione, passo dopo passo, di nuove e importanti informazioni derivanti dai bacini strumentati coinvolti nell’analisi. I risultati dimostrano l’utilità della metodologia proposta; si vede infatti che, in fase di validazione sul bacino considerato non strumentato, è possibile raggiungere un buona concordanza tra le serie di portata simulate e osservate.
Spatial homogeneity of rainfall-runoff model parameters can be a practical and valuable solution in order to assess water availability of a region. Hydrological simulation is indeed an handy tool but it is critical as it usually requires some degree of calibration. Calibration of spatially distributed models, that are particularly useful to describe the variability of physical processes that play a role in runoff generation, is challenging because of the high number of involved parameters. But some parameters can be homogeneous in space, therefore allowing one to reduce their total amount when multiple basins are considered. This assumption is verified on a statistical ground, making use of an MCMC algorithm to assess the parameter uncertainty; as a result the parameter distributions are with varying degrees comparable on the different catchments. When one wants to simulate the hydrological response of ungauged catchments, the hypothesis of spatial homogeneity of parameters has even more relevance; a long regionalization technique is usually applied, but we propose a cross-calibration procedure to be used at regional level. With this procedure model parameters are calibrated making use of hydrological information coming from gauged basins that are more similar to the site of interest. We want to analyze the trade-off between assuming the parameters homogeneous in space and adding new information as the cross-calibration evolves. Results show that the cross-calibration is a process well worth using; in validation in fact a good agreement is reached between observed and simulated discharges.

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27

Baratti, Emanuele <1983&gt. "Stima dei parametri di modelli idrologici mediante ottimizzazione dell’utilità." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6654/1/Tesi_BARATTI.pdf.

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Abstract:

Tradizionalmente, l'obiettivo della calibrazione di un modello afflussi-deflussi è sempre stato quello di ottenere un set di parametri (o una distribuzione di probabilità dei parametri) che massimizzasse l'adattamento dei dati simulati alla realtà osservata, trattando parzialmente le finalità applicative del modello. Nel lavoro di tesi viene proposta una metodologia di calibrazione che trae spunto dell'evidenza che non sempre la corrispondenza tra dati osservati e simulati rappresenti il criterio più appropriato per calibrare un modello idrologico. Ai fini applicativi infatti, può risultare maggiormente utile una miglior rappresentazione di un determinato aspetto dell'idrogramma piuttosto che un altro. Il metodo di calibrazione che viene proposto mira a valutare le prestazioni del modello stimandone l'utilità nell'applicazione prevista. Tramite l'utilizzo di opportune funzioni, ad ogni passo temporale viene valutata l'utilità della simulazione ottenuta. La calibrazione viene quindi eseguita attraverso la massimizzazione di una funzione obiettivo costituita dalla somma delle utilità stimate nei singoli passi temporali. Le analisi mostrano come attraverso l'impiego di tali funzioni obiettivo sia possibile migliorare le prestazioni del modello laddove ritenute di maggior interesse per per le finalità applicative previste.
In the majority of rainfall-runoff modelling applications, the objective function to be minimised in the parameterisation procedure is based on a measure of the goodness-of-fit that maximized the fit of the simulated data to the overall observed data, taking partially into account the specific model applications. The present dissertation focuses on the development and testing of an objective function based on the expected utility of the rainfall-runoff model. The method is based on the evidence that the performances of a hydrological model closely depend on the purpose of the application. For istance, the simulated data caught have different utility in a water resources management system or in a flood forecasting system. In the proposed method, at each time step, the comparison between simulated and observed data is carried out by using an “ad-hoc” utility function. The calibration is performed by maximizing the overall estimated utility of the simulated data. Different utility functions are tested and the results are compared against those obtained with traditional procedure. The results reveal that an adequate utility function allows an improvement of the model performances in the reproduction of the discharges considered most important to the purpose of the modeling application.

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28

Baratti, Emanuele <1983&gt. "Stima dei parametri di modelli idrologici mediante ottimizzazione dell’utilità." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6654/.

Full text

Abstract:

Tradizionalmente, l'obiettivo della calibrazione di un modello afflussi-deflussi è sempre stato quello di ottenere un set di parametri (o una distribuzione di probabilità dei parametri) che massimizzasse l'adattamento dei dati simulati alla realtà osservata, trattando parzialmente le finalità applicative del modello. Nel lavoro di tesi viene proposta una metodologia di calibrazione che trae spunto dell'evidenza che non sempre la corrispondenza tra dati osservati e simulati rappresenti il criterio più appropriato per calibrare un modello idrologico. Ai fini applicativi infatti, può risultare maggiormente utile una miglior rappresentazione di un determinato aspetto dell'idrogramma piuttosto che un altro. Il metodo di calibrazione che viene proposto mira a valutare le prestazioni del modello stimandone l'utilità nell'applicazione prevista. Tramite l'utilizzo di opportune funzioni, ad ogni passo temporale viene valutata l'utilità della simulazione ottenuta. La calibrazione viene quindi eseguita attraverso la massimizzazione di una funzione obiettivo costituita dalla somma delle utilità stimate nei singoli passi temporali. Le analisi mostrano come attraverso l'impiego di tali funzioni obiettivo sia possibile migliorare le prestazioni del modello laddove ritenute di maggior interesse per per le finalità applicative previste.
In the majority of rainfall-runoff modelling applications, the objective function to be minimised in the parameterisation procedure is based on a measure of the goodness-of-fit that maximized the fit of the simulated data to the overall observed data, taking partially into account the specific model applications. The present dissertation focuses on the development and testing of an objective function based on the expected utility of the rainfall-runoff model. The method is based on the evidence that the performances of a hydrological model closely depend on the purpose of the application. For istance, the simulated data caught have different utility in a water resources management system or in a flood forecasting system. In the proposed method, at each time step, the comparison between simulated and observed data is carried out by using an “ad-hoc” utility function. The calibration is performed by maximizing the overall estimated utility of the simulated data. Different utility functions are tested and the results are compared against those obtained with traditional procedure. The results reveal that an adequate utility function allows an improvement of the model performances in the reproduction of the discharges considered most important to the purpose of the modeling application.

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29

Cipolla, Sara Simona <1983&gt. "Tetti verdi: Analisi sperimentale e Modellazione numerica." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7179/1/CIPOLLA_SARA_SIMONA_TESI_DOTTORATO.pdf.

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Abstract:

I tetti verdi rappresentano, sempre più frequentemente, una tecnologia idonea alla mitigazione alle problematiche connesse all’ urbanizzazione, tuttavia la conoscenza delle prestazioni dei GR estensivi in clima sub-Mediterraneo è ancora limitata. La presente ricerca è supportata da 15 mesi di analisi sperimentali su due GR situati presso la Scuola di Ingegneria di Bologna. Inizialmente vengono comparate, tra loro e rispetto a una superficie di riferimento (RR), le prestazioni idrologiche ed energetiche dei due GR, caratterizzati da vegetazione a Sedum (SR) e a erbe native perenni (NR). Entrambi riducono i volumi defluiti e le temperature superficiali. Il NR si dimostra migliore del SR sia in campo idrologico che termico, la fisiologia della vegetazione del NR determina l'apertura diurna degli stomi e conseguentemente una maggiore evapotraspirazione (ET). Successivamente si sono studiate la variazioni giornaliere di umidità nel substrato del SR riscontrando che la loro ampiezza è influenzata dalla temperatura, dall’umidità iniziale e dalla fase vegetativa. Queste sono state simulate mediante un modello idrologico basato sull'equazione di bilancio idrico e su due modelli convenzionali per la stima della ET potenziale combinati con una funzione di estrazione dell’ umidità dal suolo. Sono stati proposti dei coefficienti di correzione, ottenuti per calibrazione, per considerare le differenze tra la coltura di riferimento e le colture nei GR durante le fasi di crescita. Infine, con l’ausilio di un modello implementato in SWMM 5.1. 007 utilizzando il modulo Low Impact Development (LID) durante simulazioni in continuo (12 mesi) si sono valutate le prestazioni in termini di ritenzione dei plot SR e RR. Il modello, calibrato e validato, mostra di essere in grado di riprodurre in modo soddisfacente i volumi defluiti dai due plot. Il modello, a seguito di una dettagliata calibrazione, potrebbe supportare Ingegneri e Amministrazioni nella valutazioni dei vantaggi derivanti dall'utilizzo dei GR.
Green roofs (GRs) are an increasingly popular method for mitigating the negative environmental impacts of urbanization, however literature still shows a limited knowledge on the behavior of extensive GR under sub-Mediterranean climate. This experimental study is supported by 15 months of field monitoring activity within two large GRs located on the engineering laboratories of the University of Bologna, Italy. Firstly native perennial herbs mix (NR) and succulent Sedum mix (SR) plots were compared to each other and with a bare-bituminous membrane control plot (RR) to evaluate their hydrological behaviour and diurnal cooling effects. Both the GRs are able to reduce the runoff and the surface temperature, moreover the native mix seems to achieve a better cooling service and a higher retention capacity due to his transpiration physiology which determines greater daily evapotranspiration (ET) losses. Secondly the study investigates how the moisture content in the Sedum green roof varies during dry periods due to ET. Daily moisture loss rates were influenced by temperature, initial moisture content and vegetation growth stages. Subsequently it is demonstrated that the observed moisture content data can be accurately simulated using an hydrologic model based on water balance and two conventional Potential ET models (Hargreaves and Penman-Monteith) combined with a soil moisture function. Specific monthly correction factors have been proposed to account for differences between GR and standard reference crops during the growth stages. Finally, the retention performances of SR and RR plots were simulated continuously (12 months) using the Stormwater Management Model (SWMM) with Low Impact Development (LID) controls module (version 5.1.007). The model, calibrated and validated with the experimental data, shows satisfactory results in terms of annual simulated runoff volume. It can be, after a proper calibration, a valid tool to support engineers and administrators to evaluate the benefits deriving from the use of GRs.

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30

Cipolla, Sara Simona <1983&gt. "Tetti verdi: Analisi sperimentale e Modellazione numerica." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7179/.

Full text

Abstract:

I tetti verdi rappresentano, sempre più frequentemente, una tecnologia idonea alla mitigazione alle problematiche connesse all’ urbanizzazione, tuttavia la conoscenza delle prestazioni dei GR estensivi in clima sub-Mediterraneo è ancora limitata. La presente ricerca è supportata da 15 mesi di analisi sperimentali su due GR situati presso la Scuola di Ingegneria di Bologna. Inizialmente vengono comparate, tra loro e rispetto a una superficie di riferimento (RR), le prestazioni idrologiche ed energetiche dei due GR, caratterizzati da vegetazione a Sedum (SR) e a erbe native perenni (NR). Entrambi riducono i volumi defluiti e le temperature superficiali. Il NR si dimostra migliore del SR sia in campo idrologico che termico, la fisiologia della vegetazione del NR determina l'apertura diurna degli stomi e conseguentemente una maggiore evapotraspirazione (ET). Successivamente si sono studiate la variazioni giornaliere di umidità nel substrato del SR riscontrando che la loro ampiezza è influenzata dalla temperatura, dall’umidità iniziale e dalla fase vegetativa. Queste sono state simulate mediante un modello idrologico basato sull'equazione di bilancio idrico e su due modelli convenzionali per la stima della ET potenziale combinati con una funzione di estrazione dell’ umidità dal suolo. Sono stati proposti dei coefficienti di correzione, ottenuti per calibrazione, per considerare le differenze tra la coltura di riferimento e le colture nei GR durante le fasi di crescita. Infine, con l’ausilio di un modello implementato in SWMM 5.1. 007 utilizzando il modulo Low Impact Development (LID) durante simulazioni in continuo (12 mesi) si sono valutate le prestazioni in termini di ritenzione dei plot SR e RR. Il modello, calibrato e validato, mostra di essere in grado di riprodurre in modo soddisfacente i volumi defluiti dai due plot. Il modello, a seguito di una dettagliata calibrazione, potrebbe supportare Ingegneri e Amministrazioni nella valutazioni dei vantaggi derivanti dall'utilizzo dei GR.
Green roofs (GRs) are an increasingly popular method for mitigating the negative environmental impacts of urbanization, however literature still shows a limited knowledge on the behavior of extensive GR under sub-Mediterranean climate. This experimental study is supported by 15 months of field monitoring activity within two large GRs located on the engineering laboratories of the University of Bologna, Italy. Firstly native perennial herbs mix (NR) and succulent Sedum mix (SR) plots were compared to each other and with a bare-bituminous membrane control plot (RR) to evaluate their hydrological behaviour and diurnal cooling effects. Both the GRs are able to reduce the runoff and the surface temperature, moreover the native mix seems to achieve a better cooling service and a higher retention capacity due to his transpiration physiology which determines greater daily evapotranspiration (ET) losses. Secondly the study investigates how the moisture content in the Sedum green roof varies during dry periods due to ET. Daily moisture loss rates were influenced by temperature, initial moisture content and vegetation growth stages. Subsequently it is demonstrated that the observed moisture content data can be accurately simulated using an hydrologic model based on water balance and two conventional Potential ET models (Hargreaves and Penman-Monteith) combined with a soil moisture function. Specific monthly correction factors have been proposed to account for differences between GR and standard reference crops during the growth stages. Finally, the retention performances of SR and RR plots were simulated continuously (12 months) using the Stormwater Management Model (SWMM) with Low Impact Development (LID) controls module (version 5.1.007). The model, calibrated and validated with the experimental data, shows satisfactory results in terms of annual simulated runoff volume. It can be, after a proper calibration, a valid tool to support engineers and administrators to evaluate the benefits deriving from the use of GRs.

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31

Pugliese, Alessio <1986&gt. "Tecniche innovative a base geostatistica per la stima dei deflussi idrici superficiali in bacini non strumentati." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7657/1/tesi-apugliese.pdf.

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Abstract:

Il lavoro di ricerca presentato si concentra sullo sviluppo e l’applicazione a casi reali di una tecnica innovativa a base geostatistica per la stima della curva di durata delle portate in bacini non strumentati. Prendendo spunto dalle tecniche di regionalizzazione classiche basate sul metodo del deflusso indice, la metodologia proposta stima le curve di durata adimensionali nel sito non strumentato di interesse utilizzando uno schema di ponderazione kriging di curve empiriche costruite per sezioni idrometriche localizzate nelle vicinanze del sito stesso. Nel primo caso di studio, che ha riguardato una porzione limitata di territorio appenninico marchigiano comprendente 18 bacini idrografici strumentati, si è visto che la metodologia proposta presenta prestazioni confrontabili o nettamente migliori rispetto a tecniche di regionalizzazione statistica che rappresentano lo stato dell’arte dei metodi regionali per la stima delle curve di durata. Nel secondo la metodologia proposta è stata applicata negli Stati Uniti sud-orientali e confrontata con una tecnica regionale di regressione lineare dei quantili, che è quella di riferimento proposta dal USGS. L’obiettivo è la valutazione delle prestazioni delle metodologia per un'area molto vasta che comprende 182 stazioni idrometriche nel Sud-Est degli Stati Uniti. Nella terza applicazione la metodologia proposta è utilizzata come strumento di correzione di serie idrometriche in un'area di studio del Tirolo (Austria/Italia), prodotte da modelli-afflussi capaci di simulare serie continue di portata media giornaliera. In questo contesto la metodologia è stata accoppiata ad una tecnica innovativa che stima una curva di durata dei residui, ossia la curva risultante dalla differenza tra la curva empirica e stimata con il metodo proposto, nel sito di interesse e ricostruisce una serie modificata di deflussi partendo dalla serie simulata dal modello.
The research work focuses on the design and development of a novel geostatistical approach for the prediction of flow duration curves in ungauged basins. Inspired by classical regionalization techniques based on the “index- low” method, the proposed approach is capable of predicting unbiased dimensionless flow-duration curves in ungauged sites by using a traditional kriging linear-weighting scheme of empirical curves that can be constructed at gauged sistes located in the neighborhood of the target site. The geostatistical weights are obtained by implementing an interpolation procedure of a point index that describes shape and main features of the curve. The procedure has been tested on three different case studies through three applications. The first case study, which covered a limited portion within the Marche Region, includes 18 gauged river basins and focused on the general applicability of the proposed approach. The main outcome is that the proposed method performs as well as or better than the statistical regionalization techniques representing the state of the art for the prediction of flow-duration curves. The second application focuses on a comparison with a multivariate regional technique based on linear regression analysis, which is the reference approach implemented by the USGS. The final aim of this experiment is to evaluate the performances of the methodology for a vast area that includes 182 streamgauges in the South-East of United States. In the third application, the prediction of flow-duration curves in ungauged sites is used as a correction tool for daily streamflow series obtained through continuous rainfall-runoff simulation. In this context, the methodology has been blended with an innovative technique that estimates a “residual-duration curve” for the target site and reconstructs a modified runoff series from the simulated one.

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32

Pugliese, Alessio <1986&gt. "Tecniche innovative a base geostatistica per la stima dei deflussi idrici superficiali in bacini non strumentati." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7657/.

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Abstract:

Il lavoro di ricerca presentato si concentra sullo sviluppo e l’applicazione a casi reali di una tecnica innovativa a base geostatistica per la stima della curva di durata delle portate in bacini non strumentati. Prendendo spunto dalle tecniche di regionalizzazione classiche basate sul metodo del deflusso indice, la metodologia proposta stima le curve di durata adimensionali nel sito non strumentato di interesse utilizzando uno schema di ponderazione kriging di curve empiriche costruite per sezioni idrometriche localizzate nelle vicinanze del sito stesso. Nel primo caso di studio, che ha riguardato una porzione limitata di territorio appenninico marchigiano comprendente 18 bacini idrografici strumentati, si è visto che la metodologia proposta presenta prestazioni confrontabili o nettamente migliori rispetto a tecniche di regionalizzazione statistica che rappresentano lo stato dell’arte dei metodi regionali per la stima delle curve di durata. Nel secondo la metodologia proposta è stata applicata negli Stati Uniti sud-orientali e confrontata con una tecnica regionale di regressione lineare dei quantili, che è quella di riferimento proposta dal USGS. L’obiettivo è la valutazione delle prestazioni delle metodologia per un'area molto vasta che comprende 182 stazioni idrometriche nel Sud-Est degli Stati Uniti. Nella terza applicazione la metodologia proposta è utilizzata come strumento di correzione di serie idrometriche in un'area di studio del Tirolo (Austria/Italia), prodotte da modelli-afflussi capaci di simulare serie continue di portata media giornaliera. In questo contesto la metodologia è stata accoppiata ad una tecnica innovativa che stima una curva di durata dei residui, ossia la curva risultante dalla differenza tra la curva empirica e stimata con il metodo proposto, nel sito di interesse e ricostruisce una serie modificata di deflussi partendo dalla serie simulata dal modello.
The research work focuses on the design and development of a novel geostatistical approach for the prediction of flow duration curves in ungauged basins. Inspired by classical regionalization techniques based on the “index- low” method, the proposed approach is capable of predicting unbiased dimensionless flow-duration curves in ungauged sites by using a traditional kriging linear-weighting scheme of empirical curves that can be constructed at gauged sistes located in the neighborhood of the target site. The geostatistical weights are obtained by implementing an interpolation procedure of a point index that describes shape and main features of the curve. The procedure has been tested on three different case studies through three applications. The first case study, which covered a limited portion within the Marche Region, includes 18 gauged river basins and focused on the general applicability of the proposed approach. The main outcome is that the proposed method performs as well as or better than the statistical regionalization techniques representing the state of the art for the prediction of flow-duration curves. The second application focuses on a comparison with a multivariate regional technique based on linear regression analysis, which is the reference approach implemented by the USGS. The final aim of this experiment is to evaluate the performances of the methodology for a vast area that includes 182 streamgauges in the South-East of United States. In the third application, the prediction of flow-duration curves in ungauged sites is used as a correction tool for daily streamflow series obtained through continuous rainfall-runoff simulation. In this context, the methodology has been blended with an innovative technique that estimates a “residual-duration curve” for the target site and reconstructs a modified runoff series from the simulated one.

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33

Fouial, Abdelouahid <1974&gt. "An Integrated Decision Support System for the Planning, Analysis, Management and Rehabilitation of Pressurised Irrigation Distribution Systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/7942/7/FOUIAL-PhD%20Thesis.pdf.

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Water scarcity is a mounting problem in arid and semi-arid regions such as the Mediterranean. Therefore, smarter and more effective water management is required, especially in irrigated agriculture. Irrigation infrastructure such as pressurized irrigation distribution systems (PIDSs) play an important role for the intensification of agricultural production in the Mediterranean region. However, the operation and management of these systems can be complex as they involve several intertwined processes, which need to be considered simultaneously. For this reason, numerous decision support systems (DSSs) have been developed and are available to deal with these processes, but as independent components. To this end, a comprehensive DSS called DESIDS has been developed and tested in the framework of this research. This DSS has been developed bearing in mind the need of irrigation district managers for an integrated tool that can assist them in taking strategic decisions for managing and developing reliable, adequate and sustainable water distribution plans, which provide the best services to farmers. Hence, four modules were integrated in DESIDS: i) the irrigation demand and scheduling module; ii) the hydraulic analysis module; iii) the operation and management modules; and iv) the design and rehabilitation module. DESIDS was tested on different case studies located in the Apulia region, where it proved to be a valuable tool for irrigation district managers as it provides a wide range of decision options for proper operation and management of PIDSs. All this is obtained through a DSS that offers: i) high level of interactivity; ii) complete control of the irrigation managers; iii) adaptability and flexibility to the problems related to the operation of PIDSs; and iv) effectiveness in assisting irrigation managers with the decision making. The developed DSS can be used as a platform for future integrations and expansions to include other processes needed for better decision-making support.

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Carisi, Francesca <1986&gt. "Anthropogenic Drivers of Flood-Risk Dynamics over Large Flood-Prone Areas." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/8168/7/Carisi_Francesca_Dissertation_XXIX_cicle.pdf.

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Flood risk assessment and management witnessed an extremely significant improvement during the last two decades pro-actively responding to the increasing impact of floods worldwide and to the promulgation of the European Flood Directive 2007/60/EC. In spite of these efforts, the uncertainties associated with all components of flood risk (hazard, exposure and susceptibility) are still high and several open problems still need to be accurately investigated. Addressing three different Italian case studies, this Dissertation aims at shedding some light on the most important flood risk related issues for which current literature seems to be still sparse. Concerning flood hazard, we investigates the role of different human-induced drivers and showed that the influence of anthropogenic land-subsidence near the city of Ravenna is definitely less important than the impact of the linear infrastructures in altering the flooding dynamics. With regard to flood exposure, we proposes an innovative simplified tool proving to be reliable to assess how and where a specific land-use class developed over time. By adopting these tools we investigated the evolution of exposure of residential sector over the entire floodplain of the middle-lower portion of the Po river during the last 50 years, showing that the expected economic damages in case of a catastrophic flood event doubled during this time span. Finally, focusing on flood susceptibility, we collected and analysed damage data for a real inundation event of January 2014 concerning the Secchia river to develop uni- and multi-variate damage models for flood losses evaluation. Their performance was compared with the one of widely used literature models, pointing out that the latter, originally developed for specific contexts, should not be exported to different contexts. The multi-variate approach slightly outperforms the uni-variate one. Furthermore, our results highlight the need for a comprehensive collection of post-event data, aiming at validating existing models.

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Persiano, Simone <1989&gt. "Catchment similarity and spatial correlation: added value and impacts on hydrological predictions in ungauged basins." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/8952/1/PhDThesis_SimonePersiano.pdf.

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This Thesis presents a three-fold study aimed at deepening our understanding on the added value and impacts of catchment similarity and spatial correlation (or cross-correlation) on the regional prediction of flood quantiles and flow-duration curves (FDCs) in ungauged river cross-sections. First, we consider the reference procedure for design flood estimation in Triveneto, North-eastern Italy, which assumes the entire study area to be a single hydrologically homogeneous region. We highlight that Triveneto cannot be regarded as homogeneous in terms of flood frequency regime and show that a focused-pooling approach accounting for selected geomorphoclimatic descriptors leads to regional samples with significantly improved homogeneity. Nevertheless, focused pooling does not consider the effects associated with cross-correlation, which are instead considered by Generalized Least Squares (GLS) and Top-kriging (TK; geostatistical method), although in two different ways. Recent studies show that TK outperforms GLS for predicting empirical flood quantiles, but they also speculate that cross-correlation might affect their accuracy in predicting true flood quantiles. To investigate this aspect, we apply GLS and TK for predicting flood quantiles in a homogeneous pooling-group of sites in Triveneto under different cross-correlation scenarios through a Monte Carlo experiment. For both methods, we observe that an increasing degree of spatial correlation results in an increasing masking-effect on the true flooding potential. Morever, we confirm that TK significantly outperforms GLS when they both assume flood quantiles to scale with drainage area alone, yet, both methodologies significantly improve their accuracy when considering several catchment descriptors. Finally, concerning the prediction of FDCs in a large and heterogeneous region, the Danube river basin, we show that geostatistical models provide much more accurate predictions than multi-regression models. In summary, all the analyses confirm the added value for statistical regionalisation of properly handling hydrological heterogeneity, also highlighting the pivotal role played by cross-correlation in observed streamflow time-series.

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Leoni, Paolo <1988&gt. "Machine learning per l'idrologia: applicazione del metodo random forests per la previsione degli eventi di piena fluviale con un approccio probabilistico." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/9115/1/Leoni_Paolo_Tesi.pdf.

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Le tecniche di Machine Learning sono molto utili in quanto consento di massimizzare l’utilizzo delle informazioni in tempo reale. Il metodo Random Forests può essere annoverato tra le tecniche di Machine Learning più recenti e performanti. Sfruttando le caratteristiche e le potenzialità di questo metodo, la presente tesi di dottorato affronta due casi di studio differenti; grazie ai quali è stato possibile elaborare due differenti modelli previsionali. Il primo caso di studio si è incentrato sui principali fiumi della regione Emilia-Romagna, caratterizzati da tempi di risposta molto brevi. La scelta di questi fiumi non è stata casuale: negli ultimi anni, infatti, in detti bacini si sono verificati diversi eventi di piena, in gran parte di tipo “flash flood”. Il secondo caso di studio riguarda le sezioni principali del fiume Po, dove il tempo di propagazione dell’onda di piena è maggiore rispetto ai corsi d’acqua del primo caso di studio analizzato. Partendo da una grande quantità di dati, il primo passo è stato selezionare e definire i dati in ingresso in funzione degli obiettivi da raggiungere, per entrambi i casi studio. Per l’elaborazione del modello relativo ai fiumi dell’Emilia-Romagna, sono stati presi in considerazione esclusivamente i dati osservati; a differenza del bacino del fiume Po in cui ai dati osservati sono stati affiancati anche i dati di previsione provenienti dalla catena modellistica Mike11 NAM/HD. Sfruttando una delle principali caratteristiche del metodo Random Forests, è stata stimata una probabilità di accadimento: questo aspetto è fondamentale sia nella fase tecnica che in fase decisionale per qualsiasi attività di intervento di protezione civile. L'elaborazione dei dati e i dati sviluppati sono stati effettuati in ambiente R. Al termine della fase di validazione, gli incoraggianti risultati ottenuti hanno permesso di inserire il modello sviluppato nel primo caso studio all’interno dell’architettura operativa di FEWS.
Machine Learning techniques allow to maximize the use of information in real time. The Random Forests method can be counted among the most recent and performing Machine Learning techniques. Taking advantage of the potential of this method, this PhD thesis faces two different case studies and two different forecast models have been elaborated. The first case study focused on the main rivers of the Emilia-Romagna Region, characterized by very short response times. The choice of these rivers arise from the several flood events in these basins, happened in recent years, mostly of the "flash flood" type. The second case study concerns the main sections of the Po River, where the propagation time of the flood is greater than the water courses, if compared to the first case study. Starting from a large amount of data and according to the objectives to achieve, for both case studies the first step was to select and define the input data. For the elaboration of the model to the rivers of Emilia-Romagna, the observed data have been considered. Instead, for the Po River basin, the observed data and the forecast data from the Mike11 NAM / HD model chain were exploited. Taking advantage of one of the main characteristics of the Random Forests method, a probability of occurrence has been estimated: this information is suitable both in the technical phase and in the decision-making phase for any civil protection and intervention activities. All the processing, the used data and the developed models were performed in the R environment. At the end of the validation phase, the encouraging results allowed to insert the developed model in the first case study in the operational architecture of FEWS (Flood Early Warning System).

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Tavares, Da Costa Ricardo Andre <1982&gt. "Assessment of flood hazard over large geographical areas using data-driven approaches." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amsdottorato.unibo.it/9339/1/tavaresdacosta_ricardo_tesi.pdf.

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The mapping of flood hazard can be time and resource consuming, but it is essential for assessing flood risk and for designing strategies to avoid consequences and recover faster in the event of flooding. This generally involves setting up complex numerical hydrologic/hydrodynamic models to simulate the flow of water in river channels and over the floodplains. Although such approach is considered standard, it is not always feasible. For example, it is challenging to simulate floods over large areas, produce a number of scenarios, represent flood mechanisms in a detailed way, and make use of all the data that is increasingly available in the field of water resources. Clearly, flood managers could use more options. Machine learning (i.e., algorithms that learn from data, in contrast to physically-based equations) has been seldomly used until now, but is a good candidate because of simplicity, typically faster runtimes and ability to handle large amounts of data. In combination with geographic information systems attractive tools can potentially be created. The combination of nearly instantaneous results with a web-GIS provides the possibility of near-real time analysis using any modern web browser. This thesis seek for additional clues that can help in the answering of the following questions: can data-driven models live to their expectations in flood hazard assessment? to what extent they offer viable alternatives to standard approaches and what are the concrete advantages and limitations? Several aspects of flood hazard assessment are addressed by developing and employing different state-of-the-art data-driven approaches, namely for the estimation and mapping of areas that may be subject to flooding across geographic scales, their downscaling, their extrapolation and regionalisation, or the transfer between catchments based on physical similarity. In each part of the thesis, the viability of selected methods are demonstrated and possible ways to overcome limitations are highlight.

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Shustikova, Iuliia <1988&gt. "Development and Testing of Numerical Hydrodynamic Tools for Large-scale Flood Hazard and Risk Assessment." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amsdottorato.unibo.it/9401/1/Shustikova_Iuliia_cicloXXXII.pdf.

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The increasing availability of high-resolution topographic data and the ever-growing computational potential of workstations enable us to simulate inundation events with higher accuracy across geographically larger areas. Recent studies suggest using fully two-dimensional (2D) models with high resolution in order to avoid uncertainties and limitations coming from the incorrect interpretation of flood dynamics and unrealistic reproductions of the terrain topography. Additionally, low-frequency high-magnitude events bring additional challenges as conventional structural flood protection systems (e.g. levees), which are omnipresent in floodplain landscapes, might collapse due to hydraulic conditions such as high water loads, durations and velocities, or geotechnical factors that weaken structures (e.g. burrowing animal activities). Therefore, it is important to jointly consider the distribution of the inundated zones, potential levee breaching and holistic river-system behaviour when assessing flood hazard. In order to address the abovementioned challenges the present research focuses on the high-resolution flood simulations performed on geographically large areas using 2D inundation models with a specific focus on complex topography (e.g. main and minor levee systems, embankments, artificial canals, etc.). Our study evaluates and compares numerical models of different complexity by testing them on a floodplain inundation event that occurred in the basin of the Secchia River, Northern Italy, on 19th January, 2014. Then, we test fully 2D raster-based model to simulate the event on the 350 km long stretch on the mid-lower portion of the Po River and provide insight on the input terrain resolutions, accuracy and computation time. Moreover, this Thesis aims at developing and testing a new tool, which allows for an efficient levee breach modelling and river dynamic tracking in fully 2D mode.

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Molari, Giada <1992&gt. "Innovative techniques for the hydraulic and hydrological variables assessment." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9835/1/PhD%20tesi%20-%20Giada%20Molari.pdf.

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This Thesis focues on two main research topics: (1) the use of innovative techniques for the evaluation of main hydraulic variables of natural rivers (e.g. river bathymetry, discharge, water level) and (2) the monitoring and hydrological modelling of Monate Lake (Varese, Italy).

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Neri, Mattia <1990&gt. "Innovative methodologies for enhancing the regionalisation of rainfall-runoff model parameters." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9858/1/PhDThesis_NeriMattia_final.pdf.

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The present research work focuses on the regionalisation of rainfall-runoff model parameters, fundamental for the implementation of hydrological models in ungauged basins and needed to reproduce the actual sequence of river discharge in time. Regionalisation of parameters is based on the transfer of information from hydrologically similar gauged basins to ungauged basins. This work provides further insights on parameter regionalisation and catchment similarity through the application of innovative methodologies to support the existing knowledge. The first experiment develops a methodology to test the robustness of regionalisation procedures to the availability of data in the study region. In particular, the effect of the density of streamflow gauging stations and the topological relationships between their corresponding drainage basins on the different regionalisation techniques is investigated. Such work provides useful information for the choice of the most appropriate method, based on data availability in the region. The focus is then moved to the value of hydrological similarity at sub-basin scale. Driven by the fact that similarity is generally defined between entire catchments, neglecting some significant differences in the within-basin rainfall-runoff transformation processes, a methodology to differentiate hydrological processes at sub-basin scale and to transfer model parameters from similar sub-basins is proposed. The analysis is based on the diversification of the parameter values, and therefore of the corresponding hydrological dynamics, across elevation, one of the main factors influencing the runoff generation processes. Finally, an innovative catchment signature is proposed for improving our knowledge about hydrological similarity, meant for the delineation of hydrologically similar regions. A new methodology for identifying the dominant rainfall-runoff transformation dynamics is presented: the interaction between the entire time-series of runoff generation forcings and runoff itself is quantified taking advantage of the concepts of the Information Theory and used to characterise catchments with promising results.

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Gauchery, Tugdual Tristan Nicolas Marie <1991&gt. "Submarine Landslides in the Central Mediterranean: Causes and Recurrences." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9902/1/Thesis_Tugdual-Gauchery.pdf.

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This thesis (SLATE-project, https://www.itn-slate.eu/) is concentrated on submarine landslides in the central Mediterranean Sea. Commonly found in marine and lacustrine environments, submarine landslides represent one of the main mechanisms of sediment transport along continental margins, their volumes can be far larger than any terrestrial landslides and have potential to produce far-reaching tsunamis that can rival those produced by earthquakes. However, many uncertainties remain concerning their preconditioning factors, triggering mechanisms, return frequencies and relationship with climate change as well as their geohazard potential, which vary depending on their location. Newly identified submarine landslides emplaced in the Gela Basin (GB; south of Sicily, central Mediterranean Sea) were investigated where the particular geodynamic and oceanographic context and the limited extent basin is ideal for submarine landslides research. The investigation through multiple data types including deep boreholes, multi-channel and subbottom seismic profiles, sediment cores and swath bathymetry revealed the emplacement of multiple submarine landslides during the margin outbuilding in the Pliocene-Quaternary with a drastic transition in their volumes and emplacement location at the Middle-Pleistocene Transition (MPT). This change, accompanied by an accelerated margin outbuilding from 150 to 900 m/kyr and growth of the contourite deposits, has been related to the decreasing tectonic activity at the southern front of the Maghrebian fold-and-thrust belt and the climatic changes linked to the switch to the 100-kyr Milankovitch cyclicity. Numerical in-house codes used for the reconstruction of two small-size MTDs located at the ends of the GB show similar potential of generating high-wave tsunamis that can impact the coasts of Malta and Sicily but different triggering mechanisms based on the stability analysis. A multiproxy approach made on the sediment cores revealed that strong bottom currents and very-high sedimentation rate fluctuations, associated with sea-level changes, affected the stability of contourite deposits and contributed to the recurrent emplacement of MTDs.

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Palazzoli, Irene <1988&gt. "Anthropogenic and climatic controls on surface water across the contiguous United States." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10199/1/PhDthesis_IrenePalazzoli.pdf.

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Anthropogenic activities and climatic processes heavily influence surface water resources by causing their progressive depletion, which in turn affects both societies and the environment. Therefore, there is an urgent need to understand the contribution of human and climatic dynamics on the variation of surface water availability. Here, this investigation is performed on the contiguous United States (CONUS) using remotely-sensed data. Three anthropogenic (i.e., urban area, population, and irrigation) and two climatic factors (i.e., precipitation and temperature) were selected as potential drivers of changes in surface water extent and the overlap between the increase or decrease in these drivers and the variation of surface water was examined. Most of the river basins experienced a surface water gain due to precipitation increase (eastern CONUS), and a reduction of irrigated land (western CONUS). River basins of the arid southwestern region and some river basins of the northeastern area encountered a surface water loss, essentially induced by population growth, along with a precipitation deficit and a general expansion of irrigated land. To further inspect the role of population growth and urbanization on surface water loss, the spatial interaction between human settlements and surface water depletion was examined by evaluating the frequency of surface water loss as a function of distance from urban areas. The decline of the observed frequency was successfully reproduced with an exponential distance-decay model, proving that surface water losses are more concentrated in the proximity of cities. Climatic conditions influenced this pattern, with more widely distributed losses in arid regions compared to temperate and continental areas. The results presented in this Thesis provide an improved understanding of the effects of anthropogenic and climatic dynamics on surface water availability, which could be integrated in the definition of sustainable strategies for urbanization, water management, and surface water restoration.

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RENZI, EMILIANO. "Landslide Tsunamis." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/1254.

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This study concerns several aspects of the generation and propagation of landslide tsunamis in different oceanographic topographies, i.e. an indefinite plane beach, a plane beach connecting to a flat continental platform and a conical island.

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VOLPI, FABIO. "Problematiche connesse ai deflussi urbani." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2005. http://hdl.handle.net/2108/29338.

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Uno dei punti cardine nella salvaguardia ambientale è la corretta disciplina delle acque reflue che defluiscono nei bacini urbani per effetto delle precipitazioni meteoriche e degli scarichi civili ed industriali. PArtendo dall'analisi delle tipologie di drenaggio urbano presenti sul territorio sono state approfondite le problematiche relative al trasporto solido e l'interrimento dei collettori, le problematiche di interrimento e di perdita di funzionalità delle caditoie stradali. Sono quindi proposti modelli di interpretazione dei fenomeni ed opere tipo per il presidio allo scarico delle reti fognarie.

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Galletti, Andrea. "Detailed simulation of storage hydropower systems in the Italian Alpine Region." Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/266707.

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The water-energy nexus holds paramount relevance in the context of the transition to a carbon free energy system, being water the only renewable energy source with reliable storage capacity. Modelling hydropower production in a large domain over a long time window represents an open challenge due to a variety of reasons: firstly, high-resolution, large-scale hydrological modelling in a context of uncertainty needs calibration, thus representing a computationally intensive task due to the large domain and time window over which calibration is needed; secondly, as stated by many works in literature, hydropower production modelling and in particular reservoir modelling is a very information-demanding procedure, and excessive simplifications adopted to face the lack of information might lead to consistent bias in the predictions. This thesis can be subdivided into three main parts: firstly, the model that was used to perform every analysis, HYPERstreamHS, will be presented. The model is a continuous, large-scale hydrological model embedding a dual-layer MPI framework (i.e. Message Passing Interface, a common standard in parallel computing) that ensures optimal scalability of the model, greatly reducing the computation time needed. Explicit simulation of water diversions due to hydropower production is also included in the model, and adopts only publicly available information, making the model widely applicable. Secondly, a first validation of the model will be presented, and the adopted approach will be compared with some other approaches commonly found in literature, showing that the inclusion of a high level of detail is crucial to ensure a reliable performance of the model; this first application was performed on the Adige catchment, where extensive information on human systems was available, and allowed to effectively assess which information were indispensable and which, in turn, could be simplified to some extent while preserving model performance. Finally, the model setup has been applied on a relevant portion of the Western Italian Alps; in this case, two different meteorological input forcing data sets were adopted, in order to assess the differences in their performance in terms of hydropower production modelling. This latter study indeed represents a preliminary analysis and will provide stepping stone to extend the modelling framework to the Italian Alpine Region.

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CASARTELLI, VERONICA MARIA. "La gestione dei rischi naturali: la costruzione di scenari per la pianificazione di Protezione Civile." Doctoral thesis, Università Cattolica del Sacro Cuore, 2009. http://hdl.handle.net/10280/621.

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Il presente lavoro di tesi è strutturato in tre sezioni principali. La prima, che comprende i primi due capitoli, riguarda i riferimenti per la conoscenza: al fine di definire il contesto mondiale nel quale si inserisce la tesi, vengono analizzati i dati riguardanti i disastri naturali avvenuti e quelli relativi ai possibili scenari futuri anche in relazione ai cambiamenti climatici. La seconda parte, dedicata ad approfondimenti alle scale europea e italiana, effettua nei capitoli 3-4-5 una sorta di downscaling dei primi due: la medesima struttura di analisi viene riproposta, applicata e approfondita ad una scala spaziale di maggior dettaglio, prima quella europea e successivamente quella nazionale, focalizzando l’attenzione su un particolare tipo di disastro, vale a dire le alluvioni. La terza sezione concretizza il contributo metodologico del lavoro proponendo una nuova metodologia per l’elaborazione dei piani di protezione civile comunali o intercomunali, in particolare in riferimento agli scenari di rischio idraulico, e la sua diffusione con relativa verifica applicativa.
The present study is composed of three main sections. The first, covering the first two chapters, deals with references to knowledge: in order to define the worldwide scenario to which this study is referred, data on really occurred natural disaster and on possible future events are analyzed, considering also the probable influence of the on-going climate changes. The second part, chapters 3-4-5, is a sort of downscaling to the European and Italian territory of the first two chapters’ analysis. The same methodology is detailed and implemented for the analysis of a particular event’s type: flood risk (in Europe and Italy). Third section is about the methodological contribution of the study: a new approach to civil protection planning at local level is suggested, with a particular focus on flood risk scenarios. This new civil protection planning methodology has been applied to a real context and the relative case study is presented.

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ANTOLLONI, GIULIA. "Dynamics induced by Steep Waves at a Vertical Slender Cylinder in Deep Waters: Laboratory Experiments." Doctoral thesis, Università Politecnica delle Marche, 2019. http://hdl.handle.net/11566/263694.

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In ambiente marino offshore, le onde ripide sono responsabili di episodi di danneggiamento delle strutture tanto quanto gli eventi più estremi. Un tipico fenomeno riconducibile alle onde ripide è il ringing, una risposta risonante ad alta frequenza che è stata spesso osservato in concomitanza alla presenza di un picco nella serie temporale del carico, denominato secondary load cycle (SLC), le cui cause devono essere ancora chiarite. In questa tesi, si presenta uno studio sperimentale volto all’analisi delle forze agenti, della separazione del flusso e della formazione di vortici a valle di un cilindro verticale snello, incernierato alla base, investito da onde ripide, frangenti e non, con lo scopo di chiarire la loro relazione. Si è utilizzata una innovativa e complessa configurazione di prova, che combina l’impiego di tecniche di misurazione ottica (Particle Image Velocimetry, PIV) per l’indagine del flusso a valle del cilindro su quattro piani orizzontali a diverse quote dal fondo alla registrazione sincronizzata di misure della forza agente sul cilindro e di elevazione dell’onda incidente. I risultati hanno mostrato che la separazione del flusso e la formazione di vortici si verifica per molte delle onde frangenti utilizzate e per le onde non frangenti, seppure in una forma completamente diversa. La generazione dei vortici è stata osservata subito dopo il passaggio della cresta dell’onda, a circa un quarto del periodo dell’onda, dove compare un secondo picco di carico, ovvero il SLC. La presenza del SLC è stata osservata per numeri di Froude Fr>0.6, lunghezza d’onda adimensionale kR≥0.1 e ripidità kη≥0.25, valori che ricadono all’interno dei range forniti da precedenti esperienze (Chaplin et al., 1997; Grue and Huseby, 2002; Suja-Thauvin et al., 2017; Riise et al., 2018). È stata trovata una correlazione tra la forza indotta dalla generazione dei vortici e il SLC, tuttavia la formazione dei vortici non può spiegare da sola il fenomeno. La dimensione massima dei vortici osservati è il (20-30)% del diametro del cilindro; questo risulta in disaccordo coi vortici di dimensione circa pari al diametro del cilindro osservati nelle simulazioni numeriche di Paulsen et al. (2014) e Kristiansen and Faltinsen (2017). Infine, la presenza del SLC è stata riscontrata con il ringing, indotto da effetti dovuti alla superficie libera ed alla separazione del flusso, secondo Riise et al. (2018).
Steep water waves may be responsible for damages to offshore structures, as inducing a high-frequency resonant response, commonly known as ringing, found to occur in conjunction with a peak in the load timeseries, named secondary load cycle (SLC), whose causes are still not properly known. In this thesis, an experimental study of the forces generated upon flow separation and vortex formation behind a bottom-hinged, vertical slender cylinder forced by steep waves, both breaking and non-breaking, is presented. An innovative and complex laboratory setup was arranged, this combining the use of optical measurement technique (Particle Image Velocimetry, PIV) for the investigation of the flow downstream the cylinder over four horizontal planes parallel to the bottom at different elevations with the recording of synchronized measurements both of the force acting on the cylinder and of the incoming wave elevation. PIV results showed the occurrence of flow separation and the formation of vortices for many of the breaking waves cases and for all the non-breaking waves, but with a completely different fashion. A correspondence between the SLC and the vortical structures has been found: vortex formation starts just after the wave crest has passed, at a stage corresponding to about one quarter of the wave period after the main load peak, where a second peak occurs i.e. secondary load cycle. The occurrence of a SLC has been identified by some synthetic parameters such as the Froude number Fr>0.6, the dimensionless wavenumber kR≥0.1 and the wave slope kη≥0.25, these falling within the range of limits provided by the experiences of Chaplin et al. (1997), Grue and Huseby (2002), Suja-Thauvin et al. (2017), Riise et al. (2018). A correlation between the vortex-shedding-induced force and the SLC was found, but such contribution is not the only one to the SLC. Generated vortices measure (20-30)% of the cylinder diameter at most, in disagreement with the larger size, about the cylinder diameter, of the vortices observed in the CFD simulations by Paulsen et al. (2014) and Kristiansen and Faltinsen (2017). The SLC occurrence is found to coincide with the ringing response, governed by free surface and flow separation effects, according with Riise et al. (2018).

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Tondi, Maria Cristina. "Sviluppo dello scour e sistemi di protezzione innovativi intorno a un palo eolico in ambiente marino: prove sperimentali." Doctoral thesis, Università Politecnica delle Marche, 2016. http://hdl.handle.net/11566/243103.

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Lo scopo della ricerca è quello di verificare sperimentalmente l’intensità dello scour del fondale sabbioso alla base di un palo a seguito di vari attacchi ondosi e l’efficienza dei sacchi di geotessile riempiti di sabbia (GSCs), metodo innovativo di protezione. I modelli fisici in scala 1:30 sono stati realizzati nel canale per onde del Laboratorio di Idraulica dell’UNIVPM. Sono state testate onde regolari e irregolari, con altezze H=7÷27cm e periodi T=1.8÷2.7s. Il Numero di Keulegan Carpenter KC varia da 2 a 20. I risultati confermano l’esistenza dei regimi proposti da Sumer & Fredsøe (2002), clear-water e live-bed scour. Lo scour si realizza con attacchi ondosi aventi KC>6, coincidente con l’inizio del vortex shedding. Le situazioni ondose più gravose (aventi KC=13.78 e KC=19.57) hanno originato l’abbassamento maggiore. Comparazioni dei dati sperimentali sulla profondità di scour con la formula di Sumer & Fredsøe (2002) mostrano un buon adattamento, anche se lo scour osservato evolve più rapidamente di quello predetto. Va tenuto conto che molte prove risultano influenzate dalla formazione di ripples. La protezione con GSCs è molto efficace in termini di riduzione dello scour (riduzioni dell’ordine del 80-90%). La stabilità dei GSCs è apprezzabile: essi sono stabili per onde con T=2.7s e H<20cm, mentre all’aumentare di H si sono verificati dislocamenti. I risultati sperimentali sono in disaccordo con la teoria di Recio & Oumeraci (2009), che però fa riferimento a strutture radenti. Le misure del gradiente di pressione alla base del palo hanno registrato gradienti negativi nella zona 0°-45°, dove si ha il trasporto degli horseshoe vortices, mentre a 90° e 135° essi tornano ad essere positivi, con probabilità di separazione del flusso all’interno dello strato limite. Dalle formule di Sumer & Fredsøe (1997), sono state ricavate localmente le velocità e stimati i valori di KC, che confermano come nelle zone in cui KC è maggiore si ha uno scavo più significativo.
Laboratory experiments were devoted to investigate the emergence and development of scour at the base of a slender pile immersed within an erodible bed and exposed to waves. The efficiency of geotextile sand containers (GSCs) placed around the base of the pile to prevent local erosion was also analyzed. The experiments were performed in the wave flume of the Hydraulics Laboratory of the UNIVPM. Regular and irregular waves were tested, with heights H=7÷27cm and periods T=1.8÷2.7s. The Keulegan Carpenter Number KC ranged from 2 to 20. The results confirm some far-field nearbed transport for dimensionless shear stresses exceeding the threshold Shields parameter ϑ_cr (live bed scour). The scour occurs with KC>6, corresponding to the onset of vortex shedding. The heaviest wave exposures (with KC=13.78 and KC=19.57) resulted in the deepest lowering recorded. Comparisons of the experimental data concerning the scour depths with the formula proposed by Sumer & Fredsoe (2002) have shown a good agreement. It should be noted that many tests have been influenced by the formation of ripples. The trend of the experimental scour depth is qualitatively similar to that of the theoretical curve of Sumer et al. (1992). However, during the early stages of evolution the experimental scour hole deepens faster that the predictions. The protection with GSCs turns out to be very effective in terms of reduction of scour. Moreover, they were found stable for waves having T=2.7s and H<20cm, while increasing H displacements occurred. The experimental results disagree with the hypotheses proposed by Recio & Oumeraci (2009), estimated by the authors considering the condition of seawall and not properly suitable for the configuration examined. At the base of the pile the negative pressure gradients were recorded in the area 0°-45°, where transport occurs of the horseshoe vortices and the gradients switches back to positive values at 90° and 135°, with likely separation of the flow within the boundary layer. Calculations with the formulae of Sumer & Fredsoe (1997) made it possible to locally compute the flow speeds and estimate KC, which confirmed that in the areas where KC is greater a larger scour is found.

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Mazzacani, Valentina. "La gestione delle acque nell'industria ceramica: il caso di studio della Florim Ceramiche SpA." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.

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L'acqua non è solo un bene essenziale, è anche una risorsa molto versatile in grado di procurare un'ampia gamma di benefici ma al tempo stesso è importante avere la consapevolezza che si tratti di una risorsa esauribile. Uno dei suoi maggiori utilizzi è quello industriale nel quale non è di fondamentale importanza solo il quantitativo di risorsa idrica sfruttata ma anche le sue caratteristiche qualitative. Obiettivo della tesi è quello di indagare la gestione della risorsa idrica nel contesto dell'industria ceramica cercando di capire quali sono gli utilizzi principali, i quantitativi e lo standard qualitativo dell'acqua al termine del processo industriale. Un ruolo principale nell'ambito della sostenibilità ambientale è svolto dalle aziende ceramiche del territorio che sempre più acquisiscono know-how ambientale e si adottano di procedure e tecnologie in grado di salvaguardare il territorio in cui operano. A tal fine ho condotto uno studio su una delle maggiori aziende del distretto ceramico di Sassuolo: Florim ceramiche s.p.a. analizzando il processo produttivo, quello depurativo e i quantitativi utilizzati cercando di capire gli ambiti di miglioramento attraverso la definizione di interventi sostenibili.

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ROCCHI, STEFANIA. "Nonlinear Transformation of Waves over a submerged bar." Doctoral thesis, Università Politecnica delle Marche, 2022. https://hdl.handle.net/11566/299871.

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La crescente necessità di utilizzare e preservare le aree costiere richiede una più approfondita conoscenza delle dinamiche costiere e una migliore capacità di modellare questi processi. Nello studio della propagazione delle onde verso riva occorre considerare la presenza di eventuali strutture di difesa della costa, come le scogliere emerse e sommerse, che modificano fortemente il campo di moto. Questa tesi ha l’obiettivo di approfondire la conoscenza dei meccanismi fisici di interazione non lineare tra onde e strutture costiere. A tal fine sono stati condotti esperimenti di laboratorio per studiare la trasformazione sia di onde monocromatiche che di onde random nella propagazione su un ostacolo sommerso. Le registrazioni della superficie libera sono state elaborate mediante analisi spettrali e bispettrali ed è stata valutata l'influenza di diversi parametri sulle interazioni non lineari delle onde, in particolare gli effetti del periodo ondoso e del frangimento. L'analisi bispettrale è stata utilizzata per esaminare la variazione spaziale dell’intensità degli accoppiamenti non lineari tra componenti armoniche nel campo d'onda che si propaga sopra e oltre la struttura. Dietro l’opera è stato osservato un comportamento diverso per onde random e monocromatiche. Per le onde random il campo d'onda può ancora essere descritto come sovrapposizione di onde statisticamente indipendenti, senza memoria degli accoppiamenti di fase che esistevano sulla struttura. Le componenti armoniche delle onde monocromatiche continuano invece ad interagire nell'area protetta ed i parametri di asimmetria variano in modo significativo a causa delle differenze di fase variabili tra le onde componenti. L'evoluzione spettrale delle onde dietro ostacoli sommersi influisce anche sulla risalita ondosa in corrispondenza della spiaggia. Una seconda campagna sperimentale è stata condotta per valutare il run-up su una pendenza impermeabile 1:20 in presenza della struttura sommersa. Il run-up osservato si correla meglio alle caratteristiche dell'onda incidente per le onde monocromatiche regolari e alle caratteristiche degli spettri trasmessi per le onde irregolari. Infatti, per le onde random le interazioni non lineari indotte dalla barra sommersa generano anche onde lunghe che influenzano la componente infragravitativa dello swash. Questo non accade per le onde monocromatiche regolari, dove la prima armonica rimane la principale forzante del run-up.
The growing demand to both utilise and preserve our coastal zones causes the need to better understand the coastal dynamics and to improve the capability to model these processes. In the study of wave propagation towards the shore, it is necessary to take into account the presence of coastal structures, such as submerged and emerged breakwaters , that strongly modify the wave field. The objective of this thesis is to increase the knowledge and the physical insight on the mechanisms of non-linear interaction between waves and coastal structures. Laboratory experiments have been carried out to study the transformations of both monochromatic and random waves during the propagation over a submerged obstacle. The free surface measurements have been elaborated by means of spectral and bispectral analyses and the influence of different wave parameters on the non-linear wave interactions has been evaluated, in particular the effects of the wave period and the wave breaking. The bispectral analysis is used to examine the spatial variation in intensity of the non-linear couplings between harmonic components in a wave field propagating over and beyond the bar. In the protected area, a different behaviour for random and monochromatic waves is observed. For random waves the bound harmonics are released and the wave field can still be described as a superposition of statistically independent waves, without memory of the phase locks which existed over the bar. Unlike irregular waves, the harmonic components of monochromatic waves continue to interact and the asymmetry parameters vary significantly as a result of the varying phase lags between the freely propagating component waves. The evolution of the wave spectrum behind submerged obstacles also affects the run-up on the beach. A second experimental campaign has been carried out to evaluate the wave run-up over a 1:20 impermeable slope in presence of the submerged bar. The observed run-up is better correlated to the incident wave characteristics for regular monochromatic waves and to the characteristics of the transmitted spectra for random waves. In fact, for random waves the non-linear interactions induced by the submerged bar also generate long waves that affect the infragravity band swash. This does not happen for regular monochromatic waves, where the first harmonic remains the main forcing of the run-up.

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Dissertations / Theses on the topic 'Costruzioni idrauliche'

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