Recent channel adjustments in alluvial rivers of Tuscany, central Italy

Abstract

Drastic channel adjustments have affected the main alluvial rivers of Tuscany (central Italy) during the 20th century. Bed-level adjustments were identified both by comparing available topographic longitudinal profiles of different years and through field observations. Changes in channel width were investigated by comparing available aerial photographs (1954 and 1993-98).Bed incision represents the dominant type of vertical adjustment, and is generalized along all the fluvial systems investigated. The Arno River system is the most affected by bed-level lowering (up to 9 m), whereas lower incision (generally less than 2 m) is observed along the rivers of the southern part of the region. Human disturbances appear to be the dominant factors of adjustments: the main phase of vertical change occurred during the period 1945-80, in concomitance with the phase of maximum sediment mining activity at the regional scale.The second dominant type of adjustment that involved most of the rivers in the region consists of a narrowing of the active channel. Based on measurements of channel width conducted on aerial photographs, 38% of the reaches analysed experienced a narrowing greater than 50% of the initial channel width. The largest values of channel narrowing were observed along initially braided or sinuous with alternate bars morphologies in the southern portion of the region.A regional scheme of channel adjustments is derived, based on initial channel morphology and on the amounts of incision and narrowing. Different styles of channel adjustments are described. Rivers that were originally sinuous with alternate bars to braided generally became adjusted by a moderate incision and a moderate to intense narrowing; in contrast, sinuous-meandering channels mainly adjusted vertically, with a minor amount of narrowing.

Geomorphological Approaches for River Management and Restoration in Italian and French Rivers

“…In Italy, systematic studies on channel adjustments were carried out from the end of the 1990s [Rinaldi and Simon, 1998;Surian, 1999;Rinaldi, 2003;Surian and Rinaldi, 2003]. More recent studies [i.e., Surian et al, 2009a] have involved a systematic analysis of channel changes over the last 200 years, on a larger number of study cases, with the aims of reconstructing the channel changes and understanding the relationship between channel adjustments and various human interventions.…”

Evolución morfo-sedimentaria del tramo medio del río Segre

“…trenzada) a ríos de cauce único y de menor sinuosidad; esta actividad facilita el acorazamiento del lecho y produce incisión y, consecuentemente, elimina además hábitats acuáticos CIG 41 (1), 2015, p. 23-62, ISSN 0211-6820 y riparios de gran interés (por ej. Piégay et al, 2009;Rinaldi, 2003). El impacto no se limita al tramo original de la extracción sino que los efectos pueden desplazarse aguas arriba y abajo (por ej.…”

Riverbank changes along the Mekong River: Remote sensing detection in the Vientiane–Nong Khai area

“…However, developments like sand mining, infrastructure building on the riverbank, artificial cutoffs, bank revetment, construction of reservoirs and land use alterations have changed the natural geomorphological dynamics of rivers (Lane and Richards, 1997;Surian, 1999;Fuller et al, 2003;Rinaldi, 2003;Li et al, 2007). As a consequence, channel stability is often threatened (Fuller et al, 2003;Grant et al, 2003;Kesel, 2003;Rinaldi, 2003). Such human activities could be stronger forces for change than natural events such as floods, droughts and landslides (Surian and Rinaldi, 2003).…”