This study aims to investigate the complex phenomenon of erosion as a consequence of a flood event. The chosen case study is that of the Misa River basin in the Marche region, at whose outlet rises the city of Senigallia (AN) following the exceptional flood event of September 2022. The erosion phenomenon represents a critical geomorphic process, which produces the modification at the morphological level of the basin. In addition to having a strong environmental impact, this process also has strong implications on the level of human settlements, as many civil works are allocated near river courses and bank, such as roads, buildings, or bridges. The alterations can produce damage to structures. This thesis investigates the main causes of erosion, starting from an analysis of the characteristics of the riverbed by analyzing the solid transport due to the water current, which transfers sediments up to the closure section. It then moves on to an examination of the September 2022 flood event, which revealed a profound link to climate change since the storm examined was classified as V-shaped that usually characterizes tropical storms. In order to understand the reasons of this phenomenon, the rise of sea temperatures and the peculiar morphological setting of a costal basin enclosed by the Apennine Mountain range are considered. The analysis of these data enabled the study of the entire basin using the physically-based SWAT model. The software, which is supported by a QGIS interface, allows any basin to be hydrogeologically analyzed. Through it, it is possible to produce maps showing daily, monthly and annual trends of the main characteristics of the river network, such as mean and peak flow and eroded volumes, starting with total flow and declining into bank and bed erosion. For bank erosion, bank width shortening in meters was also evaluated. In conclusion, this thesis helps to demonstrate how SWAT can prove to be a very useful and versatile tool for the purpose of estimating and analyzing the relationship between inflows and outflows in any basin following a flood event. The greatest potential could also be revealed in the area of forecasting future scenarios, either through the use of hypothetical rainfall data or as a result of changes at the geologic level of the basin.
Questo studio si propone di indagare la complessità del fenomeno dell'erosione come conseguenza di un evento alluvionale. Il caso studio scelto è quello del bacino del fiume Misa nella regione Marche, alla cui foce sorge la città di Senigallia (AN), a seguito dell'eccezionale evento alluvionale del settembre 2022. Il fenomeno erosivo è classificato come processo geomorfico, ovvero che produce la modifica a livello morfologico del bacino. Oltre ad avere un forte impatto ambientale, questo processo ha anche forti implicazioni a livello degli insediamenti umani, in quanto molte opere civili sorgono in prossimità dei corsi e delle sponde fluviali, come strade, edifici o ponti. Tali alterazioni possono produrre danni alle strutture. Questa tesi indaga inoltre le principali cause dell'erosione, partendo dall'analisi delle caratteristiche dell'alveo, analizzando il trasporto solido dovuto alla corrente d'acqua, che trasporta i sedimenti fino alla sezione di chiusura. Si passa poi all'esame dell'evento alluvionale del settembre 2022, che ha rivelato un profondo legame con i cambiamenti climatici in quanto la tempesta esaminata è stata classificata come V-shaped che solitamente caratterizza le fasce tropicali. Per comprendere le ragioni di questo fenomeno si considerano l'innalzamento della temperatura del mare e il particolare contesto morfologico, che è un bacino costale racchiuso posteriormente dalla catena montuosa appenninica. L'analisi di tutti questi dati ha permesso di studiare l'intero bacino utilizzando il modello fisico SWAT. Il software, supportato da un'interfaccia QGIS, consente di analizzare idrogeologicamente qualunque bacino. Con questo è possibile produrre mappe che mostrano le tendenze giornaliere, mensili e annuali delle principali caratteristiche della rete fluviale, quali portata media e di picco e i volumi erosi, a partire dalla portata totale fino all'erosione delle sponde e del letto. Per l'erosione delle sponde è stato valutato anche l'accorciamento della larghezza delle sponde in metri. In conclusione, questa tesi contribuisce a dimostrare come SWAT possa rivelarsi uno strumento molto utile e versatile per stimare e analizzare la relazione tra afflussi e deflussi in qualsiasi bacino a seguito di un evento di piena. Il potenziale maggiore potrebbe rivelarsi anche nell'ambito della previsione di scenari futuri, sia attraverso l'utilizzo di dati pluviometrici ipotetici, sia come risultato di cambiamenti a livello geologico del bacino.
Analysis of the erosional processes following the september 2022 flood in the Misa basin
MATTAVELLI, RICCARDO
2022/2023
Abstract
This study aims to investigate the complex phenomenon of erosion as a consequence of a flood event. The chosen case study is that of the Misa River basin in the Marche region, at whose outlet rises the city of Senigallia (AN) following the exceptional flood event of September 2022. The erosion phenomenon represents a critical geomorphic process, which produces the modification at the morphological level of the basin. In addition to having a strong environmental impact, this process also has strong implications on the level of human settlements, as many civil works are allocated near river courses and bank, such as roads, buildings, or bridges. The alterations can produce damage to structures. This thesis investigates the main causes of erosion, starting from an analysis of the characteristics of the riverbed by analyzing the solid transport due to the water current, which transfers sediments up to the closure section. It then moves on to an examination of the September 2022 flood event, which revealed a profound link to climate change since the storm examined was classified as V-shaped that usually characterizes tropical storms. In order to understand the reasons of this phenomenon, the rise of sea temperatures and the peculiar morphological setting of a costal basin enclosed by the Apennine Mountain range are considered. The analysis of these data enabled the study of the entire basin using the physically-based SWAT model. The software, which is supported by a QGIS interface, allows any basin to be hydrogeologically analyzed. Through it, it is possible to produce maps showing daily, monthly and annual trends of the main characteristics of the river network, such as mean and peak flow and eroded volumes, starting with total flow and declining into bank and bed erosion. For bank erosion, bank width shortening in meters was also evaluated. In conclusion, this thesis helps to demonstrate how SWAT can prove to be a very useful and versatile tool for the purpose of estimating and analyzing the relationship between inflows and outflows in any basin following a flood event. The greatest potential could also be revealed in the area of forecasting future scenarios, either through the use of hypothetical rainfall data or as a result of changes at the geologic level of the basin.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/210954