scholarly journals Development of a Numerical Model to Analyze the Formation and Development Process of River Mouth Bars

2021 ◽  
Vol 33 (6) ◽  
pp. 308-320
Author(s):  
Yeon-Joong Kim ◽  
Joung-Woon Woo ◽  
Jong-Sung Yoon ◽  
Myoung-Kyu Kim
Keyword(s):  
Formation Process ◽  
Numerical Models ◽  
Sediment Supply ◽  
Management Approach ◽  
Sediment Discharge ◽  
Duration Of Action ◽  
Sand Bars ◽  
Tidal Sand ◽  
Sand Bar ◽  
Bar Formation

An integrated sediment management approach that includes the recovery of the amount of declined sediment supply is effective as a fundamental solution to coastal erosion. During planning, it is essential to analyze the transfer mechanism of the sediments generated from estuaries (the junction between a river and sea) to assess the amount and rate of sediment discharge (from the river to sea) supplied back to the coast. Although numerical models that interpret the tidal sand bar flushing process during flooding have been studied, thus far, there has been no study focusing on the formation and development processes of tidal sand bars. Therefore, this study aims to construct wave deformation, flow regime calculation, and topographic change analysis models to assess the amount of recovered sediment discharge and reproduce the tidal sand bar formation process through numerical analysis for integrated littoral drift management. The tidal sand bar formation process was simulated, and the wave energy and duration of action concepts were implemented to predict the long-term littoral movement. The river flux and wave conditions during winter when tidal sand bars dominantly develop were considered as the external force conditions required for calculation. The initial condition of the topographic data directly after the Maeupcheon tidal sand bar flushing during flooding was set as the initial topography. Consequently, the tidal sand bar formation and development due to nearshore currents dependent on the incident wave direction were reproduced. Approximately 66 h after the initial topography, a sand bar formation was observed at the Maengbang estuary.

scholarly journals The Sand Bar Formation and Its Impact on the Mangrove Ecosystem:A Case Study of Kadalundi Estuary of Kadalundi River Basin in Kerala, India

2016 ◽  
Vol 11 (1) ◽  
pp. 65-71 ◽  
Author(s):  
K B. Bindu ◽  
G Jayapal
Keyword(s):  
Avicennia Marina ◽  
Mangrove Ecosystem ◽  
Urban Waste ◽  
Sand Bars ◽  
Mangrove Ecosystems ◽  
Mangrove Vegetation ◽  
Sand Bar ◽  
Kerala State ◽  
Bar Formation

Mangrove ecosystems are prone to die due to both anthropogenic and natural effects. The present study is a case study of how the formation of sand bars affects the natural mangrove ecosystem and becoming a threat to its rich biodiversity of flora and fauna. The Kadalundi – Vallikkunnu Community Reserve located in Kozhikode and Malappuram Districts in Kerala State is the first community reserve of Kerala, declared in 2007 which spread across 1.5 sq. km. andthis area includes Kadalundi bird sanctuary, mangroves and estuarine. These area mainly affected by numerous biotic interferences like over fishing, collection of oyster and mussels, mining of sand and lime and also retting of coconut. The formation of sand bars at the mouth of the river has resulted in the massive die back of the mangrove vegetation, especially that of Avicennia Marina which is one of the five species of mangroves found in the Kadalundi – Vallikunnu community reserve. The illegal utilization of land for coconut plantation, urbanization and dumping of urban waste near the mouth of the river had made the problem highly complicated. The present study highlights the need for urgent measures to be adopted from the authorities to ensure community participation for restoration of community reserve.

scholarly journals Process-Based Model Prediction of Coastal Dune Erosion through Parametric Calibration

2021 ◽  
Vol 9 (6) ◽  
pp. 635
Author(s):  
Hyeok Jin ◽  
Kideok Do ◽  
Sungwon Shin ◽  
Daniel Cox
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Model Performance ◽  
Coastal Dunes ◽  
Wave Transformation ◽  
Storm Event ◽  
Face Model ◽  
Dune Erosion ◽  
Simulation Performance ◽  
Sand Bar

Coastal dunes are important morphological features for both ecosystems and coastal hazard mitigation. Because understanding and predicting dune erosion phenomena is very important, various numerical models have been developed to improve the accuracy. In the present study, a process-based model (XBeachX) was tested and calibrated to improve the accuracy of the simulation of dune erosion from a storm event by adjusting the coefficients in the model and comparing it with the large-scale experimental data. The breaker slope coefficient was calibrated to predict cross-shore wave transformation more accurately. To improve the prediction of the dune erosion profile, the coefficients related to skewness and asymmetry were adjusted. Moreover, the bermslope coefficient was calibrated to improve the simulation performance of the bermslope near the dune face. Model performance was assessed based on the model-data comparisons. The calibrated XBeachX successfully predicted wave transformation and dune erosion phenomena. In addition, the results obtained from other two similar experiments on dune erosion with the same calibrated set matched well with the observed wave and profile data. However, the prediction of underwater sand bar evolution remains a challenge.

scholarly journals THE EFFECT OF THE INITIAL BED PERTURBTION TO THE SAND BAR FORMATION AND EVOLUTION PROCESS

2007 ◽  
Vol 51 ◽  
pp. 1045-1050
Author(s):  
Kensuke KOBAYASHI ◽  
Yasuyuki SHIMIZU ◽  
Sanjay GIRI ◽  
Yasuharu WATANABE
Keyword(s):  
Evolution Process ◽  
Formation And Evolution ◽  
Sand Bar ◽  
Bar Formation

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

2020 ◽  
Vol 70 (3) ◽  
pp. 127-139
Author(s):  
Md. Yousuf Gazi ◽  
Himel Roy ◽  
Md. Bodruddoza Mia ◽  
Syed Humayun Akhter
Keyword(s):  
River System ◽  
Policy Makers ◽  
Geospatial Techniques ◽  
Sand Bars ◽  
Multi Temporal ◽  
Migration Dynamics ◽  
Major River ◽  
River Confluences ◽  
Sand Bar ◽  
Landsat Satellite

Abstract 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.

EXPERIMENTAL STUDY OF BAR FORMATION IN SAND BED CHANNEL

2016 ◽  
Vol 78 (5-3) ◽  
Author(s):  
Duratul Ain Tholibon ◽  
Junaidah Ariffin ◽  
Jazuri Abdullah ◽  
Juliana Idrus
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
Experimental Work ◽  
Large Scale ◽  
Sediment Supply ◽  
Hydraulic Characteristics ◽  
Flow Rates ◽  
Physical Mechanisms ◽  
Bed Slope ◽  
Bar Formation

A large number of studies both theoretical and experimental have been devoted to understand the physical mechanisms underlying the bar formation. This can be investigated by carrying out an experimental work in an erodible sand bed channel using a large-scale physical river model. The study included the various hydraulic characteristics with steady flow rates and sediment supply. An experimental work consists of four matrices of flow rate and channel width with other variables namely grains size and bed slope were kept constant. Details of bar profile development that generated using Surfer, a software used for 3D elevation plots are included.

scholarly journals How do basin margins record long-term tectonic and climatic changes?

Geology ◽  
2020 ◽  
Vol 48 (9) ◽  
pp. 893-897
Author(s):  
Jinyu Zhang ◽  
Zoltán Sylvester ◽  
Jacob Covault
Keyword(s):  
Sea Level ◽  
Numerical Models ◽  
Source Area ◽  
Climatic Changes ◽  
Steady States ◽  
Sediment Supply ◽  
Relative Sea Level ◽  
Continental Scale ◽  
Sediment Routing ◽  
Basin Margin

Abstract A long-standing goal of sedimentary geoscience is to understand how tectonic and climatic changes are reflected in basin fill. Here, we use 14 numerical models of continental-scale sediment-routing systems spanning millions of years to investigate the responses of sediment supply and basin sedimentation to changes in uplift and precipitation in the source area. We also investigate the extent to which these signals can be altered by relative sea level (the sum of subsidence and eustasy). In cases of constant relative sea level, sediment supply and margin progradation have similar responses because nearly all of the sediment is transported beyond the coastal plain and continental shelf to the basin margin. Thus, margin progradation can be used as a proxy for sediment supply. However, changes in uplift and precipitation result in different erosional patterns in the source area and different basin-margin depositional patterns. Changes in uplift result in gradual (over several million years) adjustment to new steady states of source-area erosion and margin progradation, whereas changes in precipitation result in abrupt changes in erosion and progradation followed by a return to the initial steady states. In cases of changing relative sea level, sediment storage on the shelf attenuates signals of uplift, but signals of precipitation change can be interpreted in the basin-margin record because climate-induced sediment supply changes are large enough to influence margin progradation. Understanding the relationship between sediment supply and basin-margin progradation, and their linked responses to forcings, improves our ability to interpret signals of environmental change in the stratigraphic record.

scholarly journals Numerical simulation of bedload tracer transport associated with sand bar formation, bank erosion, and channel migration

2018 ◽  
Vol 40 ◽  
pp. 02013
Author(s):  
Toshiki Iwasaki ◽  
Satomi Yamaguchi ◽  
Hiroki Yabe
Keyword(s):  
Numerical Model ◽  
Bank Erosion ◽  
Bedload Transport ◽  
Transport Processes ◽  
Tracer Transport ◽  
Channel Migration ◽  
River Systems ◽  
Sand Bars ◽  
Tracer Particles ◽  
Bar Formation

An understanding of bedload transport processes is an essential research goal for better prediction of river morphology and morphodynamics as well as the transport and fate of sediment-bound materials in river systems. Passive tracer particles have been used widely to monitor bedload transport processes in rivers by measuring the spatiotemporal distribution of the bedload tracers. Here, we propose a numerical model for reproducing the transport of bedload tracers in river systems, more specifically, the behaviours of bedload tracers under the influence of complex river morphodynamics. A two-dimensional morphodynamic model is combined with a flux-based bedload tracer model with use of the active layer approach. The model is applied to a laboratory experiment that demonstrates the transport processes within the channel of bedload tracers supplied from the floodplain. The numerical model effectively reproduces the main features of the experiment, namely, the bedload tracers supplied from the floodplain due to bank erosion deposit onto sand bars developed within the channel. Because the sand bars cause a very long residence time of the bedload tracers within the bed, the transport speed of the tracers is slowed significantly under the influence of bar formation and channel migration.

scholarly journals Morphological Changes of the Lower Ping and Chao Phraya Rivers, North and Central Thailand: Flood and Coastal Equilibrium Analyses

2019 ◽  
Vol 11 (1) ◽  
pp. 152-171 ◽  
Author(s):  
Nikhom Chaiwongsaen ◽  
Parisa Nimnate ◽  
Montri Choowong
Keyword(s):  
Morphological Changes ◽  
River Mouth ◽  
Sediment Supply ◽  
Gulf Of Thailand ◽  
River Bank ◽  
Water Storage Capacity ◽  
Rainfall Condition ◽  
Sand Bar ◽  
Geomorphological Changes ◽  
Chao Phraya River

Abstract The Chao Phraya River flows in the largest river basin of Thailand and represents one of the important agricultural and industrial areas in Southeast Asia. The Ping River is one major upstream branch flowing down slope southwardly, joining the Chao Phraya River in the low-lying central plain and ending its course at the Gulf of Thailand. Surprisingly, the overflow occurs frequently and rapidly at the Lower Ping River where channel slope is high, and in particular area, sand-choked is extensively observed, even in normal rainfall condition. In contrary, at the downstream part, the erosion of river bank and shoreline around the mouth of Chao Phraya River has been spatially increasing in place where there should be a massive sediment supply to form a delta. Here we use Landsat imageries taken in 1987, 1997, 2007 and 2017 to analyze geomorphological changes of rivers. Results show that both rivers have undergone the rapid decreasing of water storage capacity and increasing of sand bar areas in river embayment. The total emerged sand bar area in the Lower Ping River increases from 1987 to 2017 up to 28.8 km2. The excessive trapped bed sediments deposition along the upper reaches is responsible for the shallower of river embankment leading to rapid overflow during flooding. At the Chao Phraya River mouth, a total of 18.8 km2 of the coastal area has been eroded from 1987 to 2017.This is caused by the reducing of sediment supply leading to non-equilibrium in the deltaic zone of the upper Gulf of Thailand. There are several possibility implications from this study involving construction of weir, in-channel sand mining, reservoir sedimentation and coastal erosion management.

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