scholarly journals Sediment dynamics of mountain streams as a function of variation in sediment deposition

2018 ◽  
Vol 55 (1) ◽  
pp. 23-29
Author(s):  
Ryunosuke Nakanishi ◽  
Yuki Okajima ◽  
Akira Baba ◽  
Yasuhiro Mitani ◽  
Hiro Ikemi
Keyword(s):  
Sediment Transport ◽  
Catchment Area ◽  
Heavy Rain ◽  
Sediment Dynamics ◽  
Sediment Deposition ◽  
Observation Data ◽  
Sediment Discharge ◽  
Regional Geology ◽  
Sediment Volume ◽  
Dam Reservoirs

 In Japan, the management of sediment in dam reservoirs has become challenging owing to heavy rain. Unexpected increase of sediment volume in dam reservoirs can increase flood risk owing to a rise in the level of the riverbed. It is therefore necessary to conduct sediment management to clarify the area of sediment production to control the amount of sediment transported and the timing of its movement. Sediment discharge from tributaries is often calculated based on catchment area and the deposited sediment volume already present in the dam reservoir. However, our preliminary surveys have implied that it is also necessary to consider regional geology in the evaluation of sediment transport. Moreover, variations in sediment deposition should be evaluated for each site where the geology changes. In this study, we observe in detail changes in the riverbed in two tributaries with different regional geologies. Changes in the shape of the riverbed were analyzed from unmanned aerial vehicle observation data, following which the effects of erosion and sedimentation on the riverbed were quantitatively evaluated. Finally, sediment discharge was calculated by a one-dimensional numerical model of sediment transport. These results indicate that the tributary that is mostly composed of mudstone produced considerably more sediment than the tributary composed mainly of sandstone. This suggests that an understanding of regional geology is necessary in the evaluation of sediment dynamics and should be considered in addition to the catchment area.

scholarly journals Large-scale suspended sediment transport and sediment deposition in the Mekong Delta

2014 ◽  
Vol 18 (8) ◽  
pp. 3033-3053 ◽  
Author(s):  
N. V. Manh ◽  
N. V. Dung ◽  
N. N. Hung ◽  
B. Merz ◽  
H. Apel
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Large Scale ◽  
Transport Model ◽  
Mekong Delta ◽  
Sediment Dynamics ◽  
Sediment Deposition ◽  
Mineral Fertilizers ◽  
Suspended Sediment Transport ◽  
Extreme Flood

Abstract. Sediment dynamics play a major role in the agricultural and fishery productivity of the Mekong Delta. However, the understanding of sediment dynamics in the delta, one of the most complex river deltas in the world, is very limited. This is a consequence of its large extent, the intricate system of rivers, channels and floodplains, and the scarcity of observations. This study quantifies, for the first time, the suspended sediment transport and sediment deposition in the whole Mekong Delta. To this end, a quasi-2D hydrodynamic model is combined with a cohesive sediment transport model. The combined model is calibrated using six objective functions to represent the different aspects of the hydraulic and sediment transport components. The model is calibrated for the extreme flood season in 2011 and shows good performance for 2 validation years with very different flood characteristics. It is shown how sediment transport and sediment deposition is differentiated from Kratie at the entrance of the delta on its way to the coast. The main factors influencing the spatial sediment dynamics are the river and channel system, dike rings, sluice gate operations, the magnitude of the floods, and tidal influences. The superposition of these factors leads to high spatial variability of sediment transport, in particular in the Vietnamese floodplains. Depending on the flood magnitude, annual sediment loads reaching the coast vary from 48 to 60% of the sediment load at Kratie. Deposited sediment varies from 19 to 23% of the annual load at Kratie in Cambodian floodplains, and from 1 to 6% in the compartmented and diked floodplains in Vietnam. Annual deposited nutrients (N, P, K), which are associated with the sediment deposition, provide on average more than 50% of mineral fertilizers typically applied for rice crops in non-flooded ring dike floodplains in Vietnam. Through the quantification of sediment and related nutrient input, the presented study provides a quantitative basis for estimating the benefits of annual Mekong floods for agriculture and fishery, and is an important piece of information with regard to the assessment of the impacts of deltaic subsidence and climate-change-related sea level rise on delta morphology.

scholarly journals Prediction of Shoreline Change for the Calculation of the Integrated Littoral Sediment Budget

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 232
Author(s):  
Yeon-Joong Kim ◽  
Jong-Sung Yoon
Keyword(s):  
Sediment Transport ◽  
Coastal Erosion ◽  
Evaluation System ◽  
Shoreline Change ◽  
Sediment Budget ◽  
Prediction Performance ◽  
Sediment Supply ◽  
Sediment Runoff ◽  
Observation Data ◽  
Sediment Volume

The severe coastal erosions are being accelerated along the east coast of South Korea owing to the intermittent erosions and depositions caused by the imbalance between the effective sediment volume supplied from coasts and rivers and the sediment transport rate. Consequently, many studies are being conducted to develop coastal-erosion reduction measures. To accurately determine the cause of coastal erosion, the causes of the erosion and deposition should be accurately diagnosed, and a comprehensive evaluation system for the sediment transport mechanism in the watershed and sea while considering regional characteristics is required. In particular, realizing the evaluation of the effective sediment volume that flows from the river to the sea through observations is a highly challenging task, and various research and developments are required to realize it, as it is still in the basic research stage. The purpose of this study was to systematically analyze the comprehensive sediment budget for coastal areas. First, an analytical system was developed. Then, a shoreline model was constructed by considering the size of the mixed particles. The parameters required for developing the model were determined using the observation data to improve the shoreline model. A sediment runoff model was applied to evaluate the effective sediment volume supplied from the river to the sea, and the applicability of this model was evaluated by comparing it with the sediment supply volume according to the soil and water assessment tool model. The representative wave and the input parameters of the model were set using the observation data of several years. It was found that the prediction performance of the shoreline change model improved when the effective sediment volume was considered, and the particles of the sediment on the shore were assumed to comprise multiple sizes. In particular, the prediction performance improved when the balance of the sediment budget was adjusted by applying a groin having a structurally similar performance to take into consideration the geographic features of the Deokbongsan (island) in front of the river mouth bar. The model demonstrated a good performance in reproducing long-term shoreline changes when the characteristics of the sea waves and the effective sediment volume were considered.

scholarly journals Estimasi Volume Sedimentasi Waduk Sermo Menggunakan Metode RUSLE, Batimetri dan Angkutan Sedimen

2020 ◽  
Vol 3 (1) ◽  
pp. 39
Author(s):  
Annisa Wulandari ◽  
Bambang Kun Cahyono
Keyword(s):  
Sediment Transport ◽  
Catchment Area ◽  
Flood Control ◽  
Volume Estimation ◽  
Rainfall Erosivity ◽  
Water Runoff ◽  
Water Catchment Area ◽  
Sediment Volume ◽  
Water Catchment ◽  
Precision Test

Sermo Reservoir is a reservoir which was built by Indonesian Government and supported by Asian Development Bank in program Integrated Irrigation Sector Project (IISP) in 1996. Sermo Reservoir functions as a flood control, raw water source and irrigation. Changes that occur to water catchment area of the Sermo Reservoir affects its condition. Especially changes that occur in aspects of water runoff, sediment production and watershed deposition of watershed aspects which are caused by erosion in water catchment area resulting in sedimentation. Long term sedimentation causes a decrease in reservoir capacity. To overcome this problem it is necessary to estimate the sedimentation volume to determine the latest condition of the Sermo Reservoir. In this activity, volume estimation of sedimentation was conducted using RUSLE, bathymetry and sediment transport methods. The data used in this activity are the data in 2016, 2017 and 2018. In this activity, the analysis of the RUSLE method in the Ngrancah Watershed includes the factors of rainfall erosivity, soil erodibility, length and slope and land cover and preservation. In addition to RUSLE, an analysis was carried out using the bathymetry method. This method calculates sedimentation based on reservoir baseline DTM data of 2017 and 2018. From the difference between both DTM epochs, obtained sediment volume and spread of Sermo Reservoir. Besides, analysis of the sediment transport method was conducted using water soil content data of 2016 which is assumed static until 2018. While analyzing with RUSLE, bathymetry and sediment transport methods using ArcGIS Software. The results of volume estimation of sedimentation using RUSLE, sediment transport and bathymetry consecutively yields 184.158,580 m3/year, 163.151,173 m3/year and 149.959,800 m3/year. Thus the estimation results of sediment thickness velocity of Sermo Reservoir using RUSLE, bathymetry and sediment transport are 8,687 mm/year, 7,790 mm/year and 7,074 mm/year. Generated volume from the methods was tested by using precision test yielding RSD 8,407 % thus classified as low accuracy. From the precision test can be concluded that sediment transport was the most precise because it has a percentage difference of -0,766 % of the average sediment volume.

scholarly journals Sediment Variation Characteristics of Major Rivers in the Middle Reaches of the Yellow River

2021 ◽  
Vol 5 (5) ◽  
pp. 20-26
Author(s):  
Yaxi Cai ◽  
Xiaodong Yang
Keyword(s):  
Sequence Analysis ◽  
Sediment Transport ◽  
River Basin ◽  
Yellow River ◽  
The Yellow River ◽  
Sediment Discharge ◽  
Variation Characteristics ◽  
Major River ◽  
Kendall Method ◽  
Hydrological Station

The sediment sequence analysis of Mann-Kendall method based on major rivers of 10 hydrological station in the middle reaches of the Yellow River [1]. The results show that: The main rivers in the middle reaches of the Yellow River hydrologic station sediment overall showed a trend of decreased significantly. Sediment discharge of all stations except Gao Jiachuan station have reached the maximum in 1956-1969s [2-3]. Among various hydrologic station sediment discharge of inter-generational are generally shows the tendency of reducing year by year. Calculate the sediment transport of major river basin of Yellow River, which average is 0.63.

scholarly journals Establishing a sediment budget in the newly created “Kleine Noordwaard” wetland area in the Rhine–Meuse delta

2018 ◽  
Vol 6 (1) ◽  
pp. 187-201 ◽  
Author(s):  
Eveline Christien van der Deijl ◽  
Marcel van der Perk ◽  
Hans Middelkoop
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Budget ◽  
Sediment Dynamics ◽  
Sediment Deposition ◽  
Created Wetlands ◽  
Intertidal Area ◽  
Soil Subsidence ◽  
Elevation Data ◽  
Marsh Erosion

Abstract. Many deltas are threatened by accelerated soil subsidence, sea-level rise, increasing river discharge, and sediment starvation. Effective delta restoration and effective river management require a thorough understanding of the mechanisms of sediment deposition, erosion, and their controls. Sediment dynamics has been studied at floodplains and marshes, but little is known about the sediment dynamics and budget of newly created wetlands. Here we take advantage of a recently opened tidal freshwater system to study both the mechanisms and controls of sediment deposition and erosion in newly created wetlands. We quantified both the magnitude and spatial patterns of sedimentation and erosion in a former polder area in which water and sediment have been reintroduced since 2008. Based on terrestrial and bathymetric elevation data, supplemented with field observations of the location and height of cut banks and the thickness of the newly deposited layer of sediment, we determined the sediment budget of the study area for the period 2008–2015. Deposition primarily took place in channels in the central part of the former polder area, whereas channels near the inlet and outlet of the area experienced considerable erosion. In the intertidal area, sand deposition especially takes place at low-lying locations close to the channels. Mud deposition typically occurs further away from the channels, but sediment is in general uniformly distributed over the intertidal area, due to the presence of topographic irregularities and micro-topographic flow paths. Marsh erosion does not significantly contribute to the total sediment budget, because wind wave formation is limited by the length of the fetch. Consecutive measurements of channel bathymetry show a decrease in erosion and deposition rates over time, but the overall results of this study indicate that the area functions as a sediment trap. The total contemporary sediment budget of the study area amounts to 35.7×103 m3 year−1, which corresponds to a net area-averaged deposition rate of 6.1 mm year−1. This is enough to compensate for the actual rates of sea-level rise and soil subsidence in the Netherlands.

scholarly journals Development of a Submerged Aquatic Vegetation Growth Model in a Coupled Wave-Current-Sediment-Transport Modeling System (COAWST v3.4)

2019 ◽  
Author(s):  
Tarandeep S. Kalra ◽  
Neil K. Ganju ◽  
Jeremy M. Testa
Keyword(s):  
Sediment Transport ◽  
Nutrient Cycling ◽  
Water Column ◽  
Submerged Aquatic Vegetation ◽  
Aquatic Vegetation ◽  
Dissolved Inorganic Carbon ◽  
Sediment Dynamics ◽  
Velocity Sedimentation ◽  
Ecosystem Change ◽  
Deterministic Modelling

Abstract. The coupled biophysical interactions between submerged aquatic vegetation (SAV), hydrodynamics (currents and waves), sediment dynamics, and nutrient cycling have long been of interest in estuarine environments. Recent observational studies have addressed feedbacks between SAV meadows, current velocity, sedimentation, and nutrient cycling and suggest SAV are ecosystem engineers whose growth can be self-reinforcing. To represent these dynamic processes in a numerical model, the presence of SAV and its effect on hydrodynamics (currents and waves) and sediment dynamics was incorporated into the open source model COAWST. In this study, we extend the COAWST modelling framework to account for dynamic changes of SAV and associated epiphyte biomass. Modelled SAV biomass is represented as a function of temperature, light, and nutrient availability and exchanges nutrients, detritus, dissolved inorganic carbon, and dissolved oxygen with the water-column biogeochemistry model. The dynamic simulation of SAV biomass allows the plants to both respond to and cause changes in water column and sediment bed properties, hydrodynamics, and sediment transport (i.e., a two-way feedback). We demonstrate the behavior of these modelled processes through application to an idealized domain, then apply the model to a eutrophic harbour where SAV dieback is a result of anthropogenic nitrate loading and eutrophication. These cases demonstrate an advance in the deterministic modelling of coupled bio-physical processes and will further our understanding of future ecosystem change.

scholarly journals Examination of Sediment Dynamics Based on the Distribution of Silica Fluxes and Flood Sediments in the Otoishi River Related to the Northern Kyushu Heavy Rain Disaster, July 2017

Geosciences ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 75
Author(s):  
Ryunosuke Nakanishi ◽  
Akira Baba ◽  
Takahiro Tsuyama ◽  
Hiro Ikemi ◽  
Yasuhiro Mitani
Keyword(s):  
Water Flow ◽  
Heavy Rain ◽  
Sediment Dynamics ◽  
The Other ◽  
Left Bank ◽  
Disaster Prevention ◽  
Dissolved Silica ◽  
Sediment Transportation ◽  
The Right ◽  
Silica Flux

The heavy rain disaster occurred in July 2017, in northern Kyushu, Japan. The river environment greatly changed due to sediment moving accompanied by erosion. It is important regarding disaster prevention to localize watersheds where sediment transportation is active. In this study, the sediment dynamics were discussed on the basis of our investigation about the stored sediment, water-flow, and silica fluxes from sub-basins. As a result, the sediment survey revealed that many sediments consist of sand or gravel and were moved secondarily by water-flow. By the hydrological survey, it was confirmed that the trend of the dissolved silica concentrations varied between the right and the left bank tributaries. It was suggested that the left bank tributaries have a various process of water-flow. Considering the distribution of collapsed slopes, the right bank tributaries have more collapsed slopes than the left bank tributaries. As suggested by the results, the range of the silica flux is wider at the left bank tributaries because the sedimentation shows various distributions. On the other hand, the right bank tributaries were estimated topographically stable since the value of the silica flux is about the same.

scholarly journals Non-Negligible Lag of Groundwater Infiltration Recharge: A Case in Mu Us Sandy Land, China

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 561 ◽  
Author(s):  
Ze-Yuan Yang ◽  
Kai Wang ◽  
Yue Yuan ◽  
Jinting Huang ◽  
Zhi-Jun Chen ◽  
...  
Keyword(s):  
Groundwater Recharge ◽  
Heavy Rain ◽  
Observation Data ◽  
Sandy Land ◽  
Mu Us Sandy Land ◽  
Recharge Sources ◽  
Matrix Flow ◽  
Lag Times ◽  
Rain Events ◽  
Storm Rainfall

Groundwater is often the main source of available water, and precipitation is one of the main recharge sources of groundwater in arid and semi-arid regions. This paper studies a fixed dune in Mu Us Sandy Land in China, establishes a numerical model, acquires hydraulic parameters and heat parameters of the vadose zone, and calculates the recharge coefficient based on field observation data and numerical modelling. These measurement results show that the response depths of storm rain are more than 90 cm, while those of small rain events are less than 10 cm. The numerical results show that infiltration depths are 10 cm for small rain and more than 90 cm for middle rain respectively. The lag time of the water content at 90 cm below the surface was 25 h following a middle rain, 18–19 h following a heavy rain, and 16–18 h following a storm rainfall. Groundwater recharge lag times (matrix flow) varied from 11 h to 48 h. Excluded precipitation for groundwater recharge was 11.25–11.75 mm in 1 h when groundwater depth was 120 cm and 15–15.5 mm when 140 cm, showing significant influence in groundwater resource evaluation.

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