New Research Sheds Light on River Dynamics and Cutoff Regimes
Boulder, Colo., USA: How are rivers characterized? Traditional methods rely on
plant forms and sedimentological techniques, focusing on deposits. Riccardo
Maitan, a Ph.D. candidate at the University of Padova, is developing a novel
approach based on river hydrological behavior, emphasizing morphodynamics.
His work aims to identify the signature of peak discharge variability—a key
hydrological metric—in meandering rivers. This research spans over 15 years
of USGS data and Google Earth image time series.
In a study recently published in
Geology, Maitan analyzes a global set of 22 rivers, totaling 5,500 km in
length, over time. This research, funded by the Italian Ministry for
Research (MIUR), is part of a larger project focused on geosciences for
sustainable development.
Bend cutoff plays a fundamental role in shaping rivers on an alluvial plain.
It buffers river sinuosity, modulates lateral migration, and affects the
surrounding stratigraphy. Most rivers exhibit one of two distinct types of
cutoffs: neck cutoffs and chute cutoffs. Neck cutoffs occur when the narrow
land bridge separating two adjacent bends is breached, a natural progression
in meander evolution. An example of a river with a neck cutoff regime is the
Purus River, an affluent of the Amazon River. Chute cutoffs, on the other
hand, occur when the river cuts a new bypass channel through its point bar,
prematurely ending the meander life cycle. The Powder River in Montana, an
affluent of the Yellowstone River, exemplifies a chute cutoff regime.
But what determines the cutoff regime of a river? Maitan et al. investigate
factors including climate and vegetation cover, concluding that the main
controlling factor is the variability of overbank discharges—the nature and
frequency of flood events. Neck cutoffs typically develop in rivers with
limited overbank discharge variability, while chute cutoffs are more common
in rivers experiencing intense, short-lived flooding.
A river’s cutoff regime leaves lasting footprints on the geomorphology of
its floodplain, making oxbow trace analysis across floodplains a potential
tool for reconstructing paleohydrologic regimes of meandering rivers based
on morphometric evidence.
The newfound correlation between a river’s hydrological variability and its
cutoff regime also underscores the need for heightened scrutiny of potential
anthropogenic impacts on river systems. Damming, for example, is often used
to reduce hydrological fluctuation for flood control. However, Maitan’s
research suggests that this practice might shift a river from a chute cutoff
regime to a neck cutoff regime, leading to more frequent bend cutoffs and a
less sinuous river. This shift also affects sediment residence time,
impacting carbon flux within the alluvial plain and potentially influencing
climate.
Maitan’s innovative research provides new insights into river dynamics and
their broader environmental implications, offering a fresh perspective on
managing and preserving riverine ecosystems.
FEATURED ARTICLE
Hydrologically driven modulation of cutoff regime in meandering rivers
Riccardo Maitan et al.
Contact: Riccardo Maitan, University of Padova, riccardo.maitan@phd.unipd.it
https://doi.org/10.1130/G51783.1
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