The study describes the geomorphological features of the Chiugena Creek basin, which is a left tributary of the Tiber River, in the proximity of the Corbara Dam (Central-Southern Umbria, Italy). In particular the fluvial dynamics processes of the riverbed, the ways of bedload transport and the related geological problems are analized. The stream flow of the Chiugena Creek is spasmodic, characterized by high variations of the discharge and by an high energy. The variability of the flow is related to lithological and structural factors: the low permeability of the bedrock and the straight main channel, controlled by a fault line, produce low runoff times and, during exceptional meteoric events, the mobilization of a large amount of clastic material in the channel. The grain size spreading into the riverbed is very high due to frequent rock falls from the slopes occurring along the middle-end reach, where the creek is enclosed between the miocenic turbiditic formations. Serious stability problems occur rather frequently along the end reach of the riverbed, where the confluence with Tiber River is characterized by a large alluvial fan. Often, in the recent past, the creek overflowed near the apex of the alluvial fan, threatening some existing buildings. The risk related to these events increases furtherly due to the Corbara Dam in the River Tiber: infact the level changes in the reservoir influence also the reach of Tiber-Chiugena confluence. The risk is particularly high when the events occur under conditions of maximum level of the reservoir: this precludes the possibility of a fast draining away of the bedload, and could involve risk conditions even for the Todi-Orvieto Road, located in the proximity of the confluence. Finally, recent stabilization works carried out along the riverbed of Chiugena Creek are considered: according to the authors they have not resulted into a significant improvement of the preexisting stability and risk conditions.
Caratteristiche geomorfologiche e dinamica fluviale del bacino del Torrente Chiugena (Umbria centro-meridionale, Italia).
CENCETTI, Corrado;CONVERSINI, Pietro;TACCONI, Paolo;
1995
Abstract
The study describes the geomorphological features of the Chiugena Creek basin, which is a left tributary of the Tiber River, in the proximity of the Corbara Dam (Central-Southern Umbria, Italy). In particular the fluvial dynamics processes of the riverbed, the ways of bedload transport and the related geological problems are analized. The stream flow of the Chiugena Creek is spasmodic, characterized by high variations of the discharge and by an high energy. The variability of the flow is related to lithological and structural factors: the low permeability of the bedrock and the straight main channel, controlled by a fault line, produce low runoff times and, during exceptional meteoric events, the mobilization of a large amount of clastic material in the channel. The grain size spreading into the riverbed is very high due to frequent rock falls from the slopes occurring along the middle-end reach, where the creek is enclosed between the miocenic turbiditic formations. Serious stability problems occur rather frequently along the end reach of the riverbed, where the confluence with Tiber River is characterized by a large alluvial fan. Often, in the recent past, the creek overflowed near the apex of the alluvial fan, threatening some existing buildings. The risk related to these events increases furtherly due to the Corbara Dam in the River Tiber: infact the level changes in the reservoir influence also the reach of Tiber-Chiugena confluence. The risk is particularly high when the events occur under conditions of maximum level of the reservoir: this precludes the possibility of a fast draining away of the bedload, and could involve risk conditions even for the Todi-Orvieto Road, located in the proximity of the confluence. Finally, recent stabilization works carried out along the riverbed of Chiugena Creek are considered: according to the authors they have not resulted into a significant improvement of the preexisting stability and risk conditions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
