scholarly journals Field data and regional modeling of sediment supply to Emilia-Romagna’s river mouths

2018 ◽  
Vol 40 ◽  
pp. 04002
Author(s):  
Silvia Cilli ◽  
Paolo Billi ◽  
Leonardo Schippa ◽  
Edoardo Grottoli ◽  
Paolo Ciavola
Keyword(s):  
Sediment Transport ◽  
Field Measurements ◽  
Sediment Supply ◽  
Shape Factors ◽  
Northern Adriatic ◽  
Load Transport ◽  
Adriatic Coast ◽  
Bed Load Transport ◽  
Bed Material ◽  
River Mouths

The Fiumi Uniti and Savio rivers are two small sandy-bed river systems which sediment yield contributes feeds part of the Emilia-Romagna beaches (Italy). Since the twentieth century the northern Adriatic coast has been affected by well-known beach retreat phenomena. As the sediment supply of these local rivers is not well known, an analysis of bed-load transport rates for the last 10 kilometres of the river has been done. Multiple analysis, supported by direct field measurements of the 2005-06 and 2017 years (still ongoing) have been realized. Complementary hydraulic investigation and modelling have been performed. Repeated bed-material samplings have been carried out during different flood conditions, obtaining a significant number of observations. Aiming at defining the behaviour of sediment-transport in these two rivers, this paper focuses on the analysis of threshold sediment transport condition. Several formulae available in literature were used to test the field measurements. All these criteria seem inappropriate to predict the threshold conditions for bed particle entrainment in terms of the value of bed shear stress. The inaccurate estimation given by these formulae is due to the fact that they do not consider natural grain-shape factors or are mainly suitable for gravel-bed rivers.

scholarly journals A reduced-complexity model for sediment transport and step-pool morphology

2016 ◽  
Author(s):  
Matteo Saletti ◽  
Peter Molnar ◽  
Marwan A. Hassan ◽  
Paolo Burlando
Keyword(s):  
Sediment Transport ◽  
Channel Morphology ◽  
Sediment Supply ◽  
Physically Based ◽  
Load Transport ◽  
Physically Based Models ◽  
Bed Load Transport ◽  
Transport Particle ◽  
Reduced Complexity ◽  
Complex Phenomena

Abstract. A new particle-based reduced-complexity model, CAST, to simulate sediment transport and channel morphology in steep streams is presented. CAST contains phenomenological parameterizations, deterministic or stochastic, of sediment supply, bed load transport, particle entrainment and deposition in a cellular-automaton space with uniform grain size. The model can reproduce a realistic bed morphology and typical fluctuations in transport rates observed in steep channels. Particle hop distances, from entrainment to deposition, are well-fitted by exponential distributions, in agreement with field data. The effect of stochasticity both in the entrainment and in the input rate is shown. A stochastic parameterization of the entrainment is essential to create and maintain a realistic channel morphology, while sediment transport in CAST shreds the input signal and its stochastic variability. A jamming routine has been added to CAST to simulate the grain-grain and grain-bed interactions that lead to particle jamming and step formation in a step-pool stream. The results show that jamming is effective in generating steps in unsteady conditions. Steps are created during high- flow periods and they survive during low flows only in sediment- starved conditions, in agreement with the jammed-state hypothesis of Church and Zimmermann (2007). Reduced-complexity models such as CAST can give new insight into the dynamics of complex phenomena (such as sediment transport and bedform stability) and be useful to test research hypotheses, being an effective complement to fully physically-based models.

scholarly journals A reduced-complexity model for sediment transport and step-pool morphology

2016 ◽  
Vol 4 (3) ◽  
pp. 549-566 ◽  
Author(s):  
Matteo Saletti ◽  
Peter Molnar ◽  
Marwan A. Hassan ◽  
Paolo Burlando
Keyword(s):  
Sediment Transport ◽  
Cellular Automaton ◽  
Channel Morphology ◽  
Sediment Supply ◽  
Physically Based ◽  
Load Transport ◽  
Physically Based Models ◽  
Bed Load Transport ◽  
Reduced Complexity ◽  
Complex Phenomena

Abstract. A new particle-based reduced-complexity model to simulate sediment transport and channel morphology in steep streams in presented. The model CAST (Cellular Automaton Sediment Transport) contains phenomenological parameterizations, deterministic or stochastic, of sediment supply, bed load transport, and particle entrainment and deposition in a cellular-automaton space with uniform grain size. The model reproduces a realistic bed morphology and typical fluctuations in transport rates observed in steep channels. Particle hop distances, from entrainment to deposition, are well fitted by exponential distributions, in agreement with field data. The effect of stochasticity in both the entrainment and the input rate is shown. A stochastic parameterization of the entrainment is essential to create and maintain a realistic channel morphology, while the intermittent transport of grains in CAST shreds the input signal and its stochastic variability. A jamming routine has been added to CAST to simulate the grain–grain and grain–bed interactions that lead to particle jamming and step formation in a step-pool stream. The results show that jamming is effective in generating steps in unsteady conditions. Steps are created during high-flow periods and they survive during low flows only in sediment-starved conditions, in agreement with the jammed-state hypothesis of Church and Zimmermann (2007). Reduced-complexity models like CAST give new insights into the dynamics of complex phenomena such as sediment transport and bedform stability and are a useful complement to fully physically based models to test research hypotheses.

scholarly journals A Shear Reynolds Number-Based Classification Method of the Nonuniform Bed Load Transport

Water ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 73 ◽  
Author(s):  
Gergely T. Török ◽  
János Józsa ◽  
Sándor Baranya
Keyword(s):  
Reynolds Number ◽  
Sediment Transport ◽  
Comparative Assessment ◽  
Bed Load ◽  
Laboratory Measurements ◽  
Strong Variation ◽  
Load Transport ◽  
Bed Load Transport ◽  
Novel Method ◽  
Bed Material

The aim of this study is to introduce a novel method which can separate sand- or gravel-dominated bed load transport in rivers with mixed-size bed material. When dealing with large rivers with complex hydrodynamics and morphodynamics, the bed load transport modes can indicate strong variation even locally, which requires a suitable approach to estimate the locally unique behavior of the sediment transport. However, the literature offers only few studies regarding this issue, and they are concerned with uniform bed load. In order to partly fill this gap, we suggest here a decision criteria which utilizes the shear Reynolds number. The method was verified with data from field and laboratory measurements, both performed at nonuniform bed material compositions. The comparative assessment of the results show that the shear Reynolds number-based method operates more reliably than the Shields–Parker diagram and it is expected to predict the sand or gravel transport domination with a <5% uncertainty. The results contribute to the improvement of numerical sediment transport modeling as well as to the field implementation of bed load transport measurements.

scholarly journals Validation of a Novel, Shear Reynolds Number Based Bed Load Transport Calculation Method for Mixed Sediments against Field Measurements

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2051 ◽  
Author(s):  
Gergely T. Török ◽  
János Józsa ◽  
Sándor Baranya
Keyword(s):  
Sediment Transport ◽  
Calculation Method ◽  
Field Measurements ◽  
Sand Transport ◽  
The Novel ◽  
Transport Models ◽  
Meaningful Improvement ◽  
Transport Calculation ◽  
Load Transport ◽  
Bed Material

In this study, the field measurement-based validation of a novel sediment transport calculation method is presented. River sections with complex bed topography and inhomogeneous bed material composition highlight the need for an improved sediment transport calculation method. The complexity of the morphodynamic features (spatially and temporally varied bed material) can result in the simultaneous appearance of the gravel and finer sand dominated sediment transport (e.g., parallel bed armoring and siltation) at different regions within a shorter river reach. For the improvement purpose of sediment transport calculation in such complex river beds, a novel sediment transport method was elaborated. The base concept of it was the combined use of two already existing empirical sediment transport models. The method was already validated against laboratory measurements. The major goal of this study was the verification of the novel method with a real river case study. The combining of the two sediment transport models was based on the implementation of a recently presented classification method of the locally dominant sediment transport nature (gravel or sand transport dominates). The results were compared with measured bed change maps. The verification clearly referred to the meaningful improvement in the sediment transport calculation by the novel manner in the case of spatially varying bed content.

scholarly journals A Shear Reynolds Number Based Investigation Method of the Bed Load Transport in Large Rivers with Complex Morphodynamics

2018 ◽  
Author(s):  
Gergely T. Török ◽  
János Józsa ◽  
Sándor Baranya
Keyword(s):  
Reynolds Number ◽  
Sediment Transport ◽  
Measurement Data ◽  
Large Rivers ◽  
Engineering Practice ◽  
Bed Load ◽  
Load Transport ◽  
Bed Load Transport ◽  
Novel Method ◽  
Bed Material

The aim of this study is to introduce a novel method which can separate sand or gravel dominated bed load transport in rivers with mixed-size bed material. In engineering practice, the Shields-Parker diagram could be used for such purposes, however, the method has certain applicability limits, due to the fact that it is based on uniform bed material and provides information rather on river-scale, instead of reach or local scale. When dealing with large rivers with complex hydrodynamics and morphodynamics the bed load transport modes can also indicate strong variation even locally, which requires a more suitable approach to estimate the locally unique behavior of the sediment transport. Here, we suggest that the decision criteria utilizes the shear Reynolds number (Re*). The method was verified against field and laboratory measurement data, both performed at non-uniform bed material compositions. The comparative assessment of the results show that the shear Reynolds number based method operates more reliably than the Shields-Parker diagram and it is expected to predict the sand or gravel transport domination with a &lt; 5% uncertainty. The introduced results can greatly contribute to the improvement of numerical sediment transport modeling as well as to the field implementation of bed load transport measurements.

scholarly journals A MULTIPLE-SIZED TRANSPORT FORMULA FOR NONUNIFORM SEDIMENTS UNDER CURRENT AND WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 34 ◽  
Author(s):  
Weiming Wu ◽  
Qianru Lin
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Size Composition ◽  
Suspended Load ◽  
Transport Rate ◽  
Bed Load ◽  
Nonuniform Sediment ◽  
Load Transport ◽  
Bed Load Transport ◽  
Bed Material

Nonuniform sediment transport exhibits difference from uniform sediment, even when the mean grain size is the same for both cases. The hiding, exposure, and armoring among different size fractions in the nonuniform bed material may significantly affect sediment transport, morphological change, bed roughness, wave dissipation, etc. It is necessary to develop multiple-sized sediment transport capacity formula to improve the accuracy and reliability of coastal analysis tools. The Wu et al. (2000) formula, which was developed for river sedimentation, is herein extended to calculate multiple-sized sediment transport under current and waves for coastal applications. This formula relates bed-load transport to the grain shear stress and suspended-load transport to the energy of the flow system. It considers the effect of bed material size composition in the hiding and exposure correction factor, which is omitted in many other existing formulas. Methods have been developed in this study to determine the bed shear stress due to waves only and combined current and waves, and in turn to compute the bed-load and suspended-load transport rates using the Wu et al. (2000) formula without changing its original formulation. The enhanced bed-load formula considers the effect of wave asymmetry on sediment transport, calculates the onshore and offshore bed-load transport rates separately and then derives the net transport rate, whereas the enhanced suspended-load formula calculates only the net transport rate due to the limit of available data. The formula has been tested using the single-sized and multiple-sized sediment transport data sets. The formula provides reliable predictions in both fractional and total transport rates. More than half of the test cases are predicted within a factor of 2 of the measured values, and more than 90% of the cases are within a factor of 5. This accuracy is generally reasonable for sediment transport under current and waves, which is very complex and little understood.

scholarly journals Regression analysis between sediment transport rates and stream discharge for the Nestos River, Greece

2013 ◽  
Vol 14 (3) ◽  
pp. 362-370
Keyword(s):  
Sediment Transport ◽  
Suspended Load ◽  
Bed Load ◽  
Regression Curve ◽  
Degree Polynomial ◽  
Stream Discharge ◽  
Nestos River ◽  
Polynomial Curve ◽  
Load Transport ◽  
Bed Load Transport

Systematic measurements of sediment transport rates and water discharge were conducted in the Nestos River (Greece), at a place located between the outlet of Nestos River basin and the river delta. This basin area is about 838 km2 and lies downstream of the Platanovrysi Dam. Separate measurements of bed load transport and suspended load transport were performed at certain cross sections of the Nestos River. In this study, relationships between sediment transport rates and stream discharge for the Nestos River are presented. A nonlinear regression curve (4th degree polynomial curve; r2 equals 0.62) between bed load transport rates and stream discharge, on the basis of 63 measurements, was developed. In addition, a nonlinear regression curve (5th degree polynomial curve; r2 equals 0.95) between suspended load transport rates and stream discharge, on the basis of 65 measurements, was developed. The relatively high r2 values indicate that both bed load transport rates and, especially, suspended load transport rates can be predicted as a function of the stream discharge in the Nestos River. However, the reliability of the regression equations would have been higher if more measured data were available.

scholarly journals Analisa Angkutan Sedimen Pada Hulu Bendung Aepodu Kabupaten Konawe Selatan

2021 ◽  
Vol 2 (1) ◽  
pp. 1-7
Author(s):  
Ramadhan Hidayat Putra ◽  
Amad Syarif Syukri ◽  
Catrin Sudarjat ◽  
Vickky Anggara Ilham
Keyword(s):  
Sediment Transport ◽  
River Flow ◽  
Suspended Load ◽  
Bedload Transport ◽  
Bed Load ◽  
Average Flow ◽  
Load Transport ◽  
Bed Load Transport ◽  
Transport Analysis

Research on Aepodu Weir Sediment Transport Analysis in South Konawe District, based on observations in the field, Aepodu Weir hasa sediment buildup that has now exceeded the height of the weirlight house. The purpose of the study was to analyze the magnitudeof Aepodu river flow and to analyze the amount of sedimenttransport that occurred in the Aepodu dam. The method used todetermine the amount of bed load transport uses stchoklitscht, whilefor transporting suspended load using forcheimer.The results of the analysis of the average flow of the Aepodu riverwere 3,604 m3/ second. Sediment transport that occurs in Aepoduweir is Bedload transport (Qb) of 291625.771 tons / year, andsuspended load transport (Qs) of 16972,423 tons / year, so that thetotal sediment transport (QT) is 308598,194 tons / year.

Test of selected bed-material load transport models: Nottawasaga River, Ontario

1994 ◽  
Vol 21 (5) ◽  
pp. 770-777 ◽  
Author(s):  
T. J. Chandler ◽  
R. A. Kostaschuk
Keyword(s):  
Sediment Transport ◽  
Engineering Application ◽  
Model Performance ◽  
Material Transport ◽  
Flow Strength ◽  
Transport Models ◽  
Data Scatter ◽  
Load Transport ◽  
Material Load ◽  
Bed Material

Predictions from 13 bed-material load sediment transport models are compared with 19 measurements of bed-material transport in Nottawasaga River, Ontario, using summary plots and geometric statistics. Model selection is based on recent engineering application and suitability for the flow and sediment conditions of the river. The models of Laursen (1958) and Yang (1979) perform best, followed by those of Ackers and White (1973). The models of Van Rijn (1984), Maddock (1976), Karim and Kennedy (1983), Brownlie (1981), and Yang (1973) have considerable data scatter. The models of Engelund and Hansen (1967) and Shen and Hung (1972) are the poorest predictors. Poor model performance is primarily due to overestimation of flow strength needed for particle entrainment and an excessively steep slope in the relations between flow strength and sediment transport. Key words: bed-material load transport models, test, Nottawasaga River.

scholarly journals SEDIMENT TRANSPORT UNDER SHEET FLOW CONDITION

1982 ◽  
Vol 1 (18) ◽  
pp. 82 ◽  
Author(s):  
Kiyoshi Horikawa ◽  
Akira Watanabe ◽  
Sadakazu Katori
Keyword(s):  
Sediment Transport ◽  
Flow Condition ◽  
Average Rate ◽  
Empirical Relationship ◽  
Sediment Concentration ◽  
Transport Rate ◽  
Sheet Flow ◽  
Load Transport ◽  
Bed Load Transport ◽  
Moving Layer

A series of laboratory experiments in an oscillatory tank was carried out to investigate the sheet flow of sediment. Objectives of the study were to determine the criterion for inception of sheet flow, and to evaluate the sediment transport rate under the sheet flow condition. In order to proceed with the investigation, it was necessary to develop devices appropriate for tracing the sediment particle movement, and for measuring the extremely dense sediment concentration in the moving layer of sheet flow. The chief results are: 1) the criteria for the inception of sheet flow given by Manohar C1955) and by Komar and Miller (1974) are both applicable to materials composed of spheroidal particles, and 2) the average rate of sediment transport for sheet flow is well described by an empirical relationship given by Madsen and Grant (1976) for the bed load transport rate on a plane bed in oscillatory flow.

Sign in / Sign up

Export Citation Format

Share Document