Study on Dynamics of River Channel and Vegetation in Gravel Bed River

Nagata, Tomonori; Watanabe, Yasuharu; Shimizu, Yasuyuki; Inoue, Takuya; Funaki, Jungo

doi:10.2208/jscejhe.72.i_1081

Cited by 8 publications

(5 citation statements)

References 3 publications

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“…Each flood had a typical duration for a mountainous region. Maximum discharge was 300 m 3 /s, which matched the average peak of the Satsunai River in Japan (Nagata et al 2016). Related parameters for the numerical simulation are summarized in Table 2.…”

Section: Simulation Scenarios and Parametersmentioning

confidence: 76%

Effects of vegetation distribution along river transects on the morphology of a gravel bed braided river

2023

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The interaction between vegetation, sediment, and water flow creates various fluvial landscapes. Hydrological conditions and flood disturbances, as well as the habitat preference of vegetation, regulate its spatial distribution. To describe the spatial distribution of vegetation cover, here, we focus on vegetation distributions along river transverse transects that define vertical and horizontal distances from water areas during low flow periods. As one of the most dynamic river types, braided rivers can be significantly influenced by vegetation encroachment. However, the effects of vegetation distributions along river transects on braided river morphology remain unknown. To study the potential influence of vegetation distribution along river transects, a depth-averaged, hydro-morphodynamic model was employed. Using the model, we investigated a medium-sized, braided river with a gravel bed affected by riparian vegetation. The following scenarios of vegetation transect distributions were examined: (1) vegetation established near or covering the low water channel, and (2) vegetation established on bar tops and kept at a distance from the low water channel. The model successfully reproduced a reduction in the braiding index for a vegetated braided river. Depending on the transect distribution scenarios employed, significantly different effects for river morphology were obtained. For example, compared to vegetation on bar tops, vegetation located near the low water channel played a more critical role for changing river morphology, redirecting water flow, and changing the statistical characteristics of the riverbed elevation distribution. Vegetation near the low water channel not only concentrated water flow to low water channels but also redirected flow to the high elevation area by reducing low water channel flow capacity. The revealed effects of the vegetation transect distribution on river morphology development helped to determine effective management protocols for reducing the negative impact of vegetation encroachment.

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Section: Simulation Scenarios and Parametersmentioning

confidence: 76%

Effects of vegetation distribution along river transects on the morphology of a gravel bed braided river

2023

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“…The authors have reported several ways for estimating the dynamic vegetation effects (i.e. Asahi et al ., ; Uchida et al ., ; Nagata et al ., ; Kang et al ., ), although this approach has not yet been incorporated into the iRIC Nays2DH model.…”

Section: Macroscale: Channelsmentioning

confidence: 96%

“…The authors have reported several ways for estimating the dynamic vegetation effects (i.e. Asahi et al, 2013;Uchida et al, 2015;Nagata et al, 2016;Kang et al, 2018), although this approach has not yet been incorporated into the iRIC Nays2DH model. Jang and Shimizu (2007) compared channel evolution without and with vegetation by means of the laboratory experiments and computational simulation as shown in Figures 27 and 28.…”

Section: Vegetation Effects On Channel Morphologymentioning

confidence: 99%

Advances in computational morphodynamics using the International River Interface Cooperative (iRIC) software

Shimizu

Nelson

Ferrel

et al. 2019

Earth Surf Processes Landf

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Results from computational morphodynamics modeling of coupled flow-bed-sediment systems are described for 10 applications as a review of recent advances in the field. Each of these applications is drawn from solvers included in the publicdomain International River Interface Cooperative (iRIC) software package. For mesoscale river features such as bars, predictions of alternate and higher mode river bars are shown for flows with equilibrium sediment supply and for a single case of oversupplied sediment. For microscale bed features such as bedforms, computational results are shown for the development and evolution of two-dimensional bedforms using a simple closure-based two-dimensional model, for two-and three-dimensional ripples and dunes using a three-dimensional large-eddy simulation flow model coupled to a physics-based particle transport model, and for the development of bed streaks using a three-dimensional unsteady Reynolds-averaged Navier-Stokes solver with a simple sedimenttransport treatment. Finally, macroscale or channel evolution treatments are used to examine the temporal development of meandering channels, a failure model for cantilevered banks, the effect of bank vegetation on channel width, the development of channel networks in tidal systems, and the evolution of bedrock channels. In all examples, computational morphodynamics results from iRIC solvers compare well to observations of natural bed morphology. For each of the three scales investigated here, brief suggestions for future work and potential research directions are offered.

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“…Where, 𝐴: The projected area of the tree, which is assumed to be (0.75 × 𝐻 3 × canopy width). 𝐶 𝑑𝑓 : the drag coefficient of the tree under the water load, which is assumed to be 1.0 10) . 𝐶 𝑑𝑤 : the drag coefficient of the tree under the wind, which is assumed to be 1.0 when the wind speed is less than 5.25m/s 12) .…”

Section: Calculating the Displacement Of Treementioning

confidence: 99%

“…Therefore, it is urgently necessary to study the mechanism of riparian destruction during the simultaneous occurrence of floods and storms. As for the relevant studies, wind damage to the tree was discussed in the forestry field [4][5][6] , and flood damage to the tree was discussed in river engineering [7][8][9][10] , there is few research about the simultaneous effect of flood and wind on the destruction of the riparian tree.…”

Section: Introductionmentioning

confidence: 99%

A Mechanical Analysis of Riparian Tree Destruction During the Simultaneous Effect of Flood and Storm

ZHOU,

TODA

2024

Journal of JSCE

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The destruction of trees in the river (riparian trees) has been mainly analyzed with consideration of flood loading recently, and the decreasing of the critical resistive moment used to evaluate the destruction condition was not analyzed in those studies though the actual resistive moment may decrease with substrate scouring by the heavy flood. In the context of climate change, which increases the likelihood of simultaneous floods and storms, the mechanism of riparian tree destruction under both flood and wind load and the change of critical resistive moment with riverbed erosion should be investigated. We established a mechanical model and analyzed the criteria for the destruction of riparian trees under flood and wind loads. One simple model was also proposed with considerations of root-soil plate radius and erosion depth of river bed to analyze the decreasing of the critical resistive moment. The taller and smaller trees are more vulnerable to be destructed than medium trees, with the consideration of both flood and storm. The critical resistive moment decreased as compared to the previous study, and the usefulness of the established model was verified to some extent.

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Study on Dynamics of River Channel and Vegetation in Gravel Bed River

Cited by 8 publications

References 3 publications

Effects of vegetation distribution along river transects on the morphology of a gravel bed braided river

Effects of vegetation distribution along river transects on the morphology of a gravel bed braided river

Advances in computational morphodynamics using the International River Interface Cooperative (iRIC) software

A Mechanical Analysis of Riparian Tree Destruction During the Simultaneous Effect of Flood and Storm

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