Experimental Study on the Hydrodynamic Influence of River Flow Confluences to the Open Channel Stage-Discharge Relationship

Wang, Xiekang; Wang, Haizhou; Yan, Xu‐Feng; Liu, Xingnian; Duan, Huan‐Feng

doi:10.20944/preprints201610.0079.v1

Cited by 4 publications

(4 citation statements)

References 21 publications

(25 reference statements)

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“…This ratio in C1 would be nearly 60% lower than in C2 (Table ), thus giving rise to superelevations of water levels and subsequent stream velocity reduction and suspended sand deposition near C1. This fact would explain the recorded sandy patches and the resulting active bed assemblage of invertebrates at this junction (although water‐surface slopes were not measured in this study, superelevations of water levels upstream of confluences have been well known for a long time; e.g., Chow, , and Wang, Wang, Yan, Liu, & Duan, ). Despite the speculative nature of the previous reasoning, it has a solid hydraulic foundation as stated before.…”

Section: Discussionmentioning

confidence: 82%

Ecological relevance of anabranch confluences: Hydrological and morphological effects

et al. 2019

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The aim of the current study was to determine the ecological role of anabranch confluences at diverse hydrological regimes, taking into consideration the floodplain secondary channels of a large river as a case of study. In conducting this study, we used unpublished data from sampling campaigns performed in the past. Triplicate benthic sediment samples were taken at each station using a bottom grab and according to sampling protocols equal to the current ones. Benthic taxa were identified at the species and genus levels. According to our results, a protracted effect by the El Niño–Southern Oscillation (ENSO) phenomenon on benthic fauna structure was evident. This effect was observed not only in the confluences but also all along the rivers, reflecting its ecological effect at least 1.5 years after its occurrence. Thus, the ENSO effect on benthic organisms should not be treated like a “physical action–reaction” but rather as an ecological relationship with lag periods (“ecological inertia”) after its occurrence. On the other hand, one of the studied confluences was categorized as a “hydro‐geomorphic patch” along the river channel, resulting from shifts in hydraulic and sedimentological conditions, which are explained by local morphological features. This hydro‐geomorphic patch created a critical site of abrupt changes in ecological patterns, enhancing the biodiversity of the river system. However, this hydro‐geomorphic patch was not detected in another anabranch confluence, where the benthic assemblage was comparable with that recorded in straight sections. Accordingly, we concluded that the mere presence of an anabranch confluence is not a sufficient reason to assume enhancing local habitat heterogeneity or biodiversity.

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Section: Discussionmentioning

confidence: 82%

Ecological relevance of anabranch confluences: Hydrological and morphological effects

et al. 2019

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“…Similarly, Wang et al . [] investigated the same phenomena in laboratory experiments and field measurements. In brief, the flow configuration along the western branch (low momentum fluxes, water superelevations and decreasing velocities), explains the massive sedimentation of suspended sand and the resulting patches emergence at cross section B, particularly during floods when most sand is transported.…”

Section: Discussionmentioning

confidence: 99%

Linking hydro‐morphology with invertebrate ecology in diverse morphological units of a large river‐floodplain system

Blettler

Amsler

Eberle

et al. 2016

Water Resources Research

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Interdisciplinary research in the fields of ecohydrology and ecogeomorphology is becoming increasingly important as a way to understand how biological and physical processes interact with each other in river systems. The objectives of the current study were 1) to determine changes in invertebrate community due to hydrological stages, 2) to link local physical features [flow configuration, sediment composition and morphological feature) with the ecological structure between and within dissimilar morphological units (meander and confluence), and 3) to determine the existence and the origin of bed hydro‐geomorphic patches, determining their ecological structure. Results were discussed in the frame of prevailing ecological models and concepts. The study site extends over a floodplain area of the large Paraná River (Argentina), including minor and major secondary channels as well as the main channel. Overall results suggested that hydrodynamics was the driving force determining distribution patterns of benthic assemblages in the floodplain. However, while the invertebrates living in minor secondary channels seem to benefit from flooding, this hydrological phase had the opposite effect on organisms from the main and major secondary channels. We also found a clear linkage between physical features and invertebrate ecology, which caused a dissimilar fauna structure between and within the meander and the confluence. Furthermore, several sandy‐patches were recorded in the confluence. These patches were colonized by the particular benthic assemblage recorded in the main channel, supported the view of rivers as patchy discontinua, under uncertain ecological equilibrium.

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“…River capacity decreases due to sediment accumulation that finally results in the modification of morphodynamics in the river confluence zone (Julien et al 2010;Mohammed et al 2011). This reduced capacity and tributaries discharge intensify flood risks due to heavy precipitation (Wang et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Assessment of Morpho-Dynamics through Geospatial Techniques within the Padma-Meghna and Ganges-Jamuna River Confluences, Bangladesh

Gazi

Roy

Mia

et al. 2020

KN J. Cartogr. Geogr. Inf.

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Bangladesh is a low-lying riverine country with the mighty Ganges–Brahmaputra–Meghna (GBM) major river system including their abundant tributaries and distributaries. Land erosion–accretion is a very common phenomenon in this riverine country. This process extensively erodes huge productive landmasses at the river confluence zones every year. The main objective of this study was to understand the confluence morpho-dynamics and identify the vulnerable areas near the Padma–Meghna Confluence (PMC) and Ganges–Jamuna confluence (GJC) due to confluence shifting and erosion–accretion phenomenon of those rivers. The present study utilized multi-temporal Landsat satellite images from 1972 to 2019 approximately ten years of interval. Results showed that the PMC indicated frequent variation in migration trend towards NW from 1972 to 1980, SE from 1980 to 2010, and then reversed towards NW direction from 2010 to 2019. On the other hand, the GJC confluence point moved NW direction (2.37 km) from the year 1972 to 1980, but from 1980 to 2019, the confluence shifted towards the SE direction. Due to the migration dynamics, huge changes happened in width and sand bars area of both confluences. In PMC, confluence width increased remarkably indicating erosive flow during 1972–1980, then progressively shortened up to 2019, indicating accretion. In contrast, GJC shows a significant accretional trend over the 47 years. The sand bar area of the PMC increased about 147.09 km2 throughout the study period. But, GJC shows an opposite scenario where the total sand bar area decreased about 51.02 km2 in the same period. From the vulnerability study of erosion–accretion scenarios, it is predicted that Paturia Ferry Ghat area, Aricha Ferry Ghat area, Arua, Baruria, Dashkin Saljana, Bhadiakola, Masundia, Khanganj and Nyakandi areas near GJC and Chandpur sadar, Srimandi, Sakhua, Bilaspur and char Atra near PMC are highly vulnerable zones. The outputs of the study will enable policy makers to take necessary measures to reduce the erosional severity on both confluence zones and could also provide a basis for proper land management.

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Experimental Study on the Hydrodynamic Influence of River Flow Confluences to the Open Channel Stage-Discharge Relationship

Cited by 4 publications

References 21 publications

Ecological relevance of anabranch confluences: Hydrological and morphological effects

Ecological relevance of anabranch confluences: Hydrological and morphological effects

Linking hydro‐morphology with invertebrate ecology in diverse morphological units of a large river‐floodplain system

Assessment of Morpho-Dynamics through Geospatial Techniques within the Padma-Meghna and Ganges-Jamuna River Confluences, Bangladesh

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