Variazioni morfologiche dell'alveo del Fiume Brenta indotte da interventi antropici

Channel changes in the Brenta River due to human interventions

Abstract

Channel evolution was analysed along the Brenta River (Northern Italy) using historical maps, aerial photographs and cross sections. The study reach, from Bassano to S. Giorgio in Bosco, is in the Upper Venetian Plain and is 23 km long. The fluvial processes and channel adjustments that occurred in the Brenta River are strongly connected to various human interventions, such as sediment mining, which was very intense in the study reach between the 1950s and the beginning of the 1980s, dams and other interventions carried out both in the drainage basin and along the river. Notwithstanding some differences within the study reach, the following reconstruction can be drawn as for channel adjustments. During the first period, from the 1950s to the beginning of the 1980s, channel incision (up to 7-8 m) and narrowing (about 50%) were the dominant processes, whereas in the more recent period (approximately the last 20 years) bed-level changes have had a lower magnitude (besides aggradation has occurred more frequently than incision) and channel widening has taken place. From cross sections was estimated that 30.7 million m³ of sediments were removed/eroded from the river bed in the period 1932-1997, but most of that process took place from the early 1950s to early 1980s, when sediment mining was very intense.