Meanders

Seminara, G.

doi:10.1017/s0022112006008925

Cited by 239 publications

(247 citation statements)

References 35 publications

Supporting

Mentioning

234

Contrasting

Order By: Relevance

“…However, unlike in other models, our flow paths are static once formed. We do not route flow around contortions in curvature (8,9) or explicitly treat means by which channel geometries evolve (17,23). Our simulations may be interpreted as initial flow paths, perhaps most readily applicable to fixed flow planforms like volcanic rilles.…”

Section: Resultsmentioning

confidence: 99%

Generic theory for channel sinuosity

Lazarus

Constantine

2013

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Sinuous patterns traced by fluid flows are a ubiquitous feature of physical landscapes on Earth, Mars, the volcanic floodplains of the Moon and Venus, and other planetary bodies. Typically discussed as a consequence of migration processes in meandering rivers, sinuosity is also expressed in channel types that show little or no indication of meandering. Sinuosity is sometimes described as "inherited" from a preexisting morphology, which still does not explain where the inherited sinuosity came from. For a phenomenon so universal as sinuosity, existing models of channelized flows do not explain the occurrence of sinuosity in the full variety of settings in which it manifests, or how sinuosity may originate. Here we present a generic theory for sinuous flow patterns in landscapes. Using observations from nature and a numerical model of flow routing, we propose that flow resistance (representing landscape roughness attributable to topography or vegetation density) relative to surface slope exerts a fundamental control on channel sinuosity that is effectively independent of internal flow dynamics. Resistance-dominated surfaces produce channels with higher sinuosity than those of slope-dominated surfaces because increased resistance impedes downslope flow. Not limited to rivers, the hypothesis we explore pertains to sinuosity as a geomorphic pattern. The explanation we propose is inclusive enough to account for a wide variety of sinuous channel types in nature, and can serve as an analytical tool for determining the sinuosity a landscape might support.geopatterns | landscape controls | threadlike flows S inuous, threadlike flows are ubiquitous features of landscapes on Earth and other planetary bodies (Fig. 1). Sinuosity is typically discussed as a consequence of channel migration processes in meandering rivers (1-9), where flow through a channel with modifiable boundaries and a curved planform sets up internal flow instabilities that drive spatial patterns of bank erosion and accretion, which change planform curvature. The physical mechanisms by which a nearly straight channel evolves into a freely meandering planform have been studied intensively and with great success. Strath terraces and meander bend cutoffs are evidence that even bedrock river channels can migrate, adjusting their sinuosity over time (10,11). Despite their prominence, rivers with migrating meanders are a subset of the sinuous channel types that exist: lunar and Venusian rilles (12, 13) are sinuous, static patterns in lava channels; drainage channels in tidal mudflats that show little or no morphologic evidence of migration behavior can be characterized as quasi-static sinuous patterns (14-16). Sinuosity in some channels is described has having been "inherited" from a preexisting morphology (10,14), but the nature of the antecedence tends to be unspecific or unexplained.If not all sinuous, threadlike flows evolve from effectively straight initial planforms, then planform sinuosity as a geomorphic trait is not inherently contingent upon a capacity ...

show abstract

Section: Resultsmentioning

confidence: 99%

Generic theory for channel sinuosity

Lazarus

Constantine

2013

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Channel planform classification based on field observations qualitatively suggests that meandering depends strongly on channel slope, grain size, bank strength, and sediment supply (2,3). Theoretical models of river meandering (2)(3)(4)(5)(6)(7)(8), however, assume that the inner and outer banks migrate at the same rate during meandering no matter the bank strength and sediment supply. The processes by which inner bank deposition keeps pace with outer bank erosion are poorly known.…”

mentioning

confidence: 99%

Experimental evidence for the conditions necessary to sustain meandering in coarse-bedded rivers

Braudrick

Dietrich

Leverich

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

315

353

View full text Add to dashboard Cite

Meandering rivers are common on Earth and other planetary surfaces, yet the conditions necessary to maintain meandering channels are unclear. As a consequence, self-maintaining meandering channels with cutoffs have not been reproduced in the laboratory. Such experimental channels are needed to explore mechanisms controlling migration rate, sinuosity, floodplain formation, and planform morphodynamics and to test theories for wavelength and bend propagation. Here we report an experiment in which meandering with near-constant width was maintained during repeated cutoff and regeneration of meander bends. We found that elevated bank strength (provided by alfalfa sprouts) relative to the cohesionless bed material and the blocking of troughs (chutes) in the lee of point bars via suspended sediment deposition were the necessary ingredients to successful meandering. Varying flood discharge was not necessary. Scaling analysis shows that the experimental meander migration was fast compared to most natural channels. This high migration rate caused nearly all of the bedload sediment to exchange laterally, such that bar growth was primarily dependent on bank sediment supplied from upstream lateral migration. The high migration rate may have contributed to the relatively low sinuosity of 1.19, and this suggests that to obtain much higher sinuosity experiments at this scale may have to be conducted for several years. Although patience is required to evolve them, these experimental channels offer the opportunity to explore several fundamental issues about river morphodynamics. Our results also suggest that sand supply may be an essential control in restoring self-maintaining, actively shifting gravel-bedded meanders.channel patterns ͉ fluvial geomorphology ͉ river meandering R iver meandering-the lateral bank shifting that produces sinuous, single-thread channels-is inherent to coupled flow and sediment transport in gravel-and sand-bedded channels within a broad range of channel width-to-depth ratios (1). Channel planform classification based on field observations qualitatively suggests that meandering depends strongly on channel slope, grain size, bank strength, and sediment supply (2, 3). Theoretical models of river meandering (2-8), however, assume that the inner and outer banks migrate at the same rate during meandering no matter the bank strength and sediment supply. The processes by which inner bank deposition keeps pace with outer bank erosion are poorly known. This is a fundamental gap in our understanding of meandering rivers.Laboratory experiments have demonstrated that channels with sand or gravel bed and banks will develop bars and planform curvature but will inevitably braid (9-11), because the weak outer banks erode faster than bars can grow and accrete to the inner bank. Braiding often develops due to flow diversion down chutes that form between the bar and the floodplain. Chutes occur because the area of maximum coarse sediment deposition is not located at the boundary between the bar and floodplain, but rather t...

show abstract

“…In general, the direction of such propagation can be both up-and downstream and is independent of the landscape's uplift/subsidence regime [Allen, 2008]. Specific examples include the up-and downstream migration of meanders (depending on the channel aspect ratio and meander wave number) [Seminara, 2006;Zolezzi and Seminara, 2001;Zolezzi et al, 2005], upstream migration of erosional fronts [Tucker and Slingerland, 1994], and upstream-propagating waves of deposition [Hoyal and Sheets, 2009]. In contrast, the spatial convolution integrals at the core of the emerging non-local models of landscape dynamics [Schumer et al, 2009;Foufoula-Georgiou et al, 2010;Voller and Paola, 2010] imply that conditions at a point may depend intrinsically on conditions elsewhere in the landscape, without the need for a wave-like propagation.…”

Section: Introductionmentioning

confidence: 99%

Does the flow of information in a landscape have direction?

Voller

Ganti

Paola

et al. 2012

Geophysical Research Letters

View full text Add to dashboard Cite

There is an emerging viewpoint that the sediment flux at a given point on the landscape may be influenced by landscape properties in a region extending away from the point of interest. Using a general sediment transport model that incorporates this non‐local nature via fractional derivatives, we find a strong asymmetry in the direction in which the non‐locality affects a given point: For erosional landscapes, physically plausible elevation profiles are obtained only when the spatial influence is restricted to the region upstream of the point of interest. By contrast, in depositional landscapes, the non‐local model is guaranteed to produce physically plausible topographic profiles only when the spatial influence is restricted to the region downstream of the point of interest. These results suggest that information flows downstream in an erosional landscape and upstream in depositional landscapes.

show abstract

Meanders

Cited by 239 publications

References 35 publications

Generic theory for channel sinuosity

Generic theory for channel sinuosity

Experimental evidence for the conditions necessary to sustain meandering in coarse-bedded rivers

Does the flow of information in a landscape have direction?

Contact Info

Product

Resources

About