Biomorphodynamic modelling of inner bank advance in migrating meander bends

Zen, Simone; Zolezzi, Guido; Toffolon, Marco; Gurnell, Angela M.

doi:10.1016/j.advwatres.2015.11.017

Cited by 45 publications

(31 citation statements)

References 76 publications

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“…In particular, our data and similar measurements from other river systems can contribute to the refinement and testing of numerical models that are increasingly incorporating physically based vegetation/morphology feedbacks and could provide important means of forecasting likely evolutionary trajectories of vegetated landforms under different environmental conditions (e.g. Van Oorschot et al, ; Zen et al, ).…”

Section: Discussionmentioning

confidence: 99%

Understanding processes of island development on an island braided river over timescales from days to decades

Gurnell

Bertoldi

Francis

et al. 2018

Earth Surf Processes Landf

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Bar colonization by vegetation and subsequent island formation is a key bio‐geomorphological process in fluvial landscape evolution. Here we investigate morphological and ecological evolution of river islands over timescales from single floods to decades, focusing on islands initiated by deposited trees that sprout to form vegetated patches. On a braided reach of the high‐energy Tagliamento River, Italy, we monitored 30 pioneer islands of 1 to 17 years age in comparison with unvegetated bar surfaces, open areas between islands, and established island surfaces. We integrated morphological, surface sediment and vegetation properties of islands initiated by different flood events, combining evidence from remotely‐sensed and ground observations, flow and climate time series. At a decadal timescale, pioneer islands aggrade rapidly to the elevation of the mean annual flood, showing a steady increase in vegetation canopy height, fining of surface sediments from predominantly gravel to silty‐sand with a notable clay and organic fraction. The standing vegetation included over 130 species, with the largest number on island surfaces of intermediate elevation and flood disturbance. As islands age, standing vegetation becomes comprised mainly of competitor species with transient seed banks and typical of woodland, scrub, pasture and wetland habitats, whereas the winter seedbank is dominated on all surfaces by ruderal species with persistent seedbanks, mainly associated with aquatic, wetland, pasture, arable and wasteland habitats. At shorter timescales, the biogeomorphological trajectory of pioneer islands is initiated by large flood events that control the elevation of deposited trees, and subsequent flows that control tree survival and establishment. Island morphological evolution depends on the frequency‐magnitude of sediment and seed delivery and redistribution by flood and possibly wind events, whereas island ability to retain sediments reflects the degree of vegetation establishment, which in the short‐term may vary with seasonal to annual moisture supply, substrate characteristics and climatic growth conditions. © 2018 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Understanding processes of island development on an island braided river over timescales from days to decades

Gurnell

Bertoldi

Francis

et al. 2018

Earth Surf Processes Landf

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“…Three sites were located at the Mocajuba settlement (M1, M2, M3) and two at the Arimbu settlement (A1, A2), distributed along a stretch of almost 7 km ( Figure 1c). The outer meander margin is typically high flow, although, in active meandering rivers, such as the Caet e, it can also be low flow, where the water depth decreases during the dry season, promoting greater river bed stability (Zen, Zolezzi, Toffolon, & Gurnell, 2016). The first zone, the meander margin (MM), was located on the outer meander margin, has a lower current velocity, between 0.01 and 0.06 m/s, an average depth of 0.99 AE 0.26 m (range 0.75-1.2 m) and 0.45 AE 0.14 m (range 0.15-0.65 m), in the wet and dry seasons, respectively, and deposition of fine sediments and a mussel bed was present.…”

Section: Study Areamentioning

confidence: 99%

Greater macroinvertebrate diversity and freshwater mussel density in meander margins of an Amazon river

et al. 2018

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Meanders are complex aquatic environments exhibiting different flow and sediment characteristics that influence macroinvertebrate distribution. Differences in macroinvertebrate composition, freshwater mussel density (mainly Castalia ambigua Lamarck, 1819) and habitat variables were investigated, using uni‐ and multivariate analyses, in two zones, the margin and thalweg, of the meanders of a 7‐km stretch of a morphologically unaltered tropical alluvial lowland river. Clear differences were found between meander zones, with greater taxonomic and functional diversity of macroinvertebrates and greater freshwater mussel densities in the meander margin. A total of 12 families of macroinvertebrates were exclusive to the meander margin, and macroinvertebrate indicators of zones were Philopotamidae and Leptoceridae (meander margin) and Chironomidae and Elmidae (meander thalweg). In the meander margin, there were no differences in macroinvertebrate abundance, and taxonomic and functional group diversity among areas with low, medium and high mussel density. Macroinvertebrate abundance did not vary between zones, but in both, abundance was associated with lower pH and higher electrical conductivity. Low shear velocity, which stabilises the river bed, high organic matter content and percentage silt in the meander margin were associated with higher taxonomic and functional macroinvertebrate diversity, as well as the presence of freshwater mussels. Natural unaltered meanders are spatially heterogeneous in both habitat and biodiversity and, similar to restored meanders, support greater macroinvertebrate taxonomic and functional diversity, as well as maintain freshwater mussel beds, mainly by stabilising the river bed. The meander margin may also be important for attracting mussel host fish that feed on macroinvertebrates and aid mussel dispersal. Thus, the meander margins, and other similar riparian habitats with low shear velocity, for example, side channels and pools, have potentially high conservation value and should be afforded due protection.

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“…The outcomes of this integrated historical and modelling analysis provide both site‐specific and more general understanding of the impacts of particular human stressors, that support biomorphodynamic modelling that addresses the mutual interplay among river morphology and riparian vegetation (e.g. Camporeale et al ., , Zen et al ., ) and contribute to future management decision‐making within regulated, channelized rivers where such interaction occurs.…”

Section: Introductionmentioning

confidence: 99%

Biomorphodynamics of alternate bars in a channelized, regulated river: An integrated historical and modelling analysis

Serlet

Gurnell

Zolezzi

et al. 2018

Earth Surf Processes Landf

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The development of alternate bars in channelized rivers can be explained theoretically as an instability of the riverbed when the active channel width to depth ratio exceeds a threshold. However, the development of a vegetation cover on the alternate bars of some channelized rivers and its interactions with bar morphology have not been investigated in detail. Our study focused on the co‐evolution of alternate bars and vegetation along a 33 km reach of the Isère River, France. We analysed historical information to investigate the development of alternate bars and their colonization by vegetation within a straightened, embanked river subject to flow regulation, sediment mining, and vegetation management. Over an 80 year period, bar density decreased, bar length increased, and bar mobility slowed. Vegetation encroachment across bar surfaces accompanied these temporal changes and, once established, vegetation cover persisted, shifting the overall system from an unvegetated to a vegetated dynamic equilibrium state. The unvegetated morphodynamics of the impressively regular sequence of alternate bars that developed in the Isère following channelization is consistent with previous theoretical morphodynamic work. However, the apparent triggering dynamics of vegetation colonization needs to be investigated, based on complex biophysical instability processes. If instability related to vegetation colonization is confirmed, further work needs to focus on the relevance of initial conditions for this instability, and on related feedback effects such as how the morphodynamics of bare‐sediment alternate bars may have affected vegetation development and, in turn, how vegetation has created a new dynamic equilibrium state. Copyright © 2018 John Wiley & Sons, Ltd.

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Biomorphodynamic modelling of inner bank advance in migrating meander bends

Cited by 45 publications

References 76 publications

Understanding processes of island development on an island braided river over timescales from days to decades

Understanding processes of island development on an island braided river over timescales from days to decades

Greater macroinvertebrate diversity and freshwater mussel density in meander margins of an Amazon river

Biomorphodynamics of alternate bars in a channelized, regulated river: An integrated historical and modelling analysis

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