TY - JOUR

T1 - Human impact and channel dynamics of a low sinuosity pseudomeandering river

AU - Billi, Paolo

AU - Bartholdy, Jesper

N1 - Funding Information: The authors are grateful to Fabrizio Vannacci and Liliana Teruggi for their valuable and restless help during the field campaigns and the grain-size analysis of the very many bed material samples collected. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Publisher Copyright: © 2024 Elsevier B.V.

PY - 2024

Y1 - 2024

N2 - Typically, pseudomeandering rivers are gravel-bed streams considered unstable and prone to turning into braided or meandering channels under the effect of external forcings. Channel changes of pseudomeandering rivers have not been investigated in detail so far. This paper analyses the response of a pseudomeandering river (the Cecina River in western central Italy) to variations of sediment supply resulting from streambed material mining and land use change throughout the last two centuries. Old maps and 11 sets of aerial images from 1954 to the present of four representative sites were used to measure the variation through time of bankfull width and channel sinuosity. The changes in the number of bends, chute channels, bank erosion, bend extension, migration and retraction were recorded and the main processes which favoured pseudomeandering river channel changes were investigated. The old maps indicate that in the first half of the XIX century, the study river had probably a braided morphology in response to the increase in sediment supply following the liberalization of deforestation. From the beginning of the XX century to the present, the river had a predominantly single thread, pseudomeandering morphology which did not change during about 20 years of intense gravel mining (the 1960s – mid-1980s) when the main response of the river was channel incision and narrowing. A few years after bed material extraction stopped the river started to widen, to increase channel sinuosity and consolidate its pseudomeandering morphology. The study confirms that marked variations in sediment supply are more effective than floods in triggering river channel changes. The study also shows that the pseudomeandering configuration is less unstable than previously highlighted in other scientific works.

AB - Typically, pseudomeandering rivers are gravel-bed streams considered unstable and prone to turning into braided or meandering channels under the effect of external forcings. Channel changes of pseudomeandering rivers have not been investigated in detail so far. This paper analyses the response of a pseudomeandering river (the Cecina River in western central Italy) to variations of sediment supply resulting from streambed material mining and land use change throughout the last two centuries. Old maps and 11 sets of aerial images from 1954 to the present of four representative sites were used to measure the variation through time of bankfull width and channel sinuosity. The changes in the number of bends, chute channels, bank erosion, bend extension, migration and retraction were recorded and the main processes which favoured pseudomeandering river channel changes were investigated. The old maps indicate that in the first half of the XIX century, the study river had probably a braided morphology in response to the increase in sediment supply following the liberalization of deforestation. From the beginning of the XX century to the present, the river had a predominantly single thread, pseudomeandering morphology which did not change during about 20 years of intense gravel mining (the 1960s – mid-1980s) when the main response of the river was channel incision and narrowing. A few years after bed material extraction stopped the river started to widen, to increase channel sinuosity and consolidate its pseudomeandering morphology. The study confirms that marked variations in sediment supply are more effective than floods in triggering river channel changes. The study also shows that the pseudomeandering configuration is less unstable than previously highlighted in other scientific works.

KW - Channel planform changes

KW - Gravel mining

KW - Land use change

KW - Pseudomeandering river

KW - Sediment supply

U2 - 10.1016/j.catena.2024.107895

DO - 10.1016/j.catena.2024.107895

M3 - Journal article

AN - SCOPUS:85186752100

VL - 239

JO - Advances in Geoecology

JF - Advances in Geoecology

SN - 0722-0723

M1 - 107895

ER -