scholarly journals A flume study to investigate the contribution of main-channel bedforms on levee formation

2018 ◽  
Vol 40 ◽  
pp. 02018 ◽  
Author(s):  
Till Branß ◽  
Francisco Núñez-González ◽  
Andreas Dittrich ◽  
Jochen Aberle
Keyword(s):  
Main Channel ◽  
Variable Geometry ◽  
Ultrasonic Sensors ◽  
River Systems ◽  
Flume Experiments ◽  
Natural Levee ◽  
Level Elevation ◽  
Bed Material ◽  
The Relationship ◽  
Flume Study

Natural levees can be observed worldwide in nearly all river systems characterized by frequent flooding in combination with the transport of suspended bed material. Several parameters and processes have been suggested to explain the formation and the highly variable geometry of natural levees. However, the effect of bedforms migrating in the main-channel has not been amongst the studied parameters and processes. To fill this gap, this study investigates the relationship between bedforms and natural levee formation by flume experiments. Experiments were conducted in a 2 m wide and 30 m long sediment recirculating flume, monitoring the bed level elevation in the main channel by ultrasonic sensors as well as recording the levee development on the floodplain by a camera. The effect of different bed configurations on the developed levees is compared, and discussed, showing that bedforms could enhance levee formation.

scholarly journals The Development of a 1-D Integrated Hydro-Mechanical Model Based on Flume Tests to Unravel Different Hydrological Triggering Processes of Debris Flows

Water ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 950 ◽  
Author(s):  
Theo van Asch ◽  
Bin Yu ◽  
Wei Hu
Keyword(s):  
Debris Flow ◽  
Mechanical Model ◽  
Debris Flows ◽  
Overland Flow ◽  
Slope Angle ◽  
Great Influence ◽  
Flume Experiments ◽  
Triggering Mechanisms ◽  
Bed Material ◽  
Triggering Process

Many studies which try to analyze conditions for debris flow development ignore the type of initiation. Therefore, this paper deals with the following questions: What type of hydro-mechanical triggering mechanisms for debris flows can we distinguish in upstream channels of debris flow prone gullies? Which are the main parameters controlling the type and temporal sequence of these triggering processes, and what is their influence on the meteorological thresholds for debris flow initiation? A series of laboratory experiments were carried out in a flume 8 m long and with a width of 0.3 m to detect the conditions for different types of triggering mechanisms. The flume experiments show a sequence of hydrological processes triggering debris flows, namely erosion and transport by intensive overland flow and by infiltrating water causing failure of channel bed material. On the basis of these experiments, an integrated hydro-mechanical model was developed, which describes Hortonian and saturation overland flow, maximum sediment transport, through flow and failure of bed material. The model was calibrated and validated using process indicator values measured during the experiments in the flume. Virtual model simulations carried out in a schematic hypothetical source area of a catchment show that slope angle and hydraulic conductivity of the bed material determine the type and sequence of these triggering processes. It was also clearly demonstrated that the type of hydrological triggering process and the influencing geometrical and hydro-mechanical parameters may have a great influence on rainfall intensity-duration threshold curves for the start of debris flows.

scholarly journals An 1-D Integrated Hydro-Mechanical Model to Unravel Different Hydrological Triggering Processes of Debris Flows

2018 ◽  
Author(s):  
Theo W.J. van Asch ◽  
Bin Yu ◽  
Wei Hu
Keyword(s):  
Mechanical Model ◽  
Debris Flows ◽  
Overland Flow ◽  
Model Simulation ◽  
Slope Angle ◽  
Great Influence ◽  
Source Area ◽  
Material Model ◽  
Flume Experiments ◽  
Bed Material

Many studies, which try to analyze the meteorological threshold conditions for debris flows ignore the type of initiation. This paper focuses on the differences in hydrological triggering processes of debris flows in channel beds of the source areas. The different triggering processes were studied in the laboratory and by model simulation on the field scale. The laboratory experiments were carried out in a flume, 8 m long and a width of 0.3 m. An integrated hydro-mechanical model was developed, describing Hortonian and Saturation overland flow, through flow, maximum sediment transport and failure of bed material. The model was tested on the processes observed in the flume. The flume experiments show a sequence of hydrological processes triggering debris flows, namely erosion and transport by intensive overland flow and by infiltrating water causing failure of channel bed material. Model simulations carried out on a schematic hypothetical source area of a catchment show that the type and sequence of these triggering processes are determined by slope angle and the hydraulic conductivity of the bed material. It was also clearly demonstrated that the type of initiation process and the geometrical and hydro-mechanical parameters may have a great influence on rainfall intensity-duration threshold curves, indicating the start of debris flows.

scholarly journals Geo-tourism Potential of Sand Bars and Oxbow lake at Buluh Cina, Kampar – Riau, Indonesia

2016 ◽  
Vol 1 (1) ◽  
pp. 59
Author(s):  
Yuniarti Yuskar
Keyword(s):  
Rain Forest ◽  
Field Survey ◽  
Main Channel ◽  
Oxbow Lake ◽  
Tourist Attraction ◽  
Natural Levee ◽  
Sand Bars ◽  
The Government ◽  
Tourism Potential ◽  
The Village

Buluh Cina Village is located at Siak Hulu District, Kampar Regency, Riau Province and its about 25 km from Pekanbaru City. This Village is designated as Tourism Village by The Government of Riau Province. This research aims to optimize the potential Geo-tourism by understanding the strengths and weaknesses aspect which is owned by Buluh China Village. So it can increase the number of tourists who visit Buluh Cina Village. The method used is the field survey and literature review. The village is surrounded by a tropical rain forest with an area of over 100 hectares and it divided by the Kampar Kanan River. Fluvial Meandering System of this river form the main channel (river), sandbars, natural levee, floodplain and oxbow lake. Geo-tourism potential that can be developed are sand bars and oxbow lake. Buluh China Village has had a tourist attraction, but there are still some weaknesses, such as floods in the rainy season and some support facilities are not optimal.

scholarly journals Analysis of sediment particle velocity in wave motion based on wave flume experiments

2012 ◽  
Vol 34 (2) ◽  
pp. 41-50
Author(s):  
Adam Krupiński
Keyword(s):  
Sediment Transport ◽  
Wave Motion ◽  
Steady Motion ◽  
Field Analysis ◽  
Flume Experiments ◽  
Mean Velocity ◽  
Single Wave ◽  
Wave Flume ◽  
Dynamic Velocity ◽  
Bed Material

Abstract The experiment described was one of the elements of research into sediment transport conducted by the Division of Geotechnics of West-Pomeranian University of Technology. The experimental analyses were performed within the framework of the project “Building a knowledge transfer network on the directions and perspectives of developing wave laboratory and in situ research using innovative research equipment” launched by the Institute of Hydroengineering of the Polish Academy of Sciences in Gdańsk. The objective of the experiment was to determine relations between sediment transport and wave motion parameters and then use the obtained results to modify formulas defining sediment transport in rivers, like Ackers-White formula, by introducing basic parameters of wave motion as the force generating bed material transport. The article presents selected results of the experiment concerning sediment velocity field analysis conducted for different parameters of wave motion. The velocity vectors of particles suspended in water were measured with a Particle Image Velocimetry (PIV) apparatus registering suspended particles in a measurement flume by producing a series of laser pulses and analysing their displacement with a high-sensitivity camera connected to a computer. The article presents velocity fields of suspended bed material particles measured in the longitudinal section of the wave flume and their comparison with water velocity profiles calculated for the definite wave parameters. The results presented will be used in further research for relating parameters essential for the description of monochromatic wave motion to basic sediment transport parameters and „transforming” mean velocity and dynamic velocity in steady motion to mean wave front velocity and dynamic velocity in wave motion for a single wave.

scholarly journals The Prediction of Fine Sediment Distribution in Gravel-Bed Rivers Using a Combination of DEM and FNN

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1515
Author(s):  
Van Hieu Bui ◽  
Minh Duc Bui ◽  
Peter Rutschmann
Keyword(s):  
Feedforward Neural Networks ◽  
Fine Sediment ◽  
Sediment Distribution ◽  
Gravel Bed ◽  
Fine Sediments ◽  
Porosity Variation ◽  
Sediment Sorting ◽  
Gravel Bed Rivers ◽  
Bed Material ◽  
The Relationship

Large amounts of fine sediment infiltration into void spaces of coarse bed material have the ability to alter the morphodynamics of rivers and their aquatic ecosystems. Modelling the mechanisms of fine sediment infiltration in gravel-bed is therefore of high significance. We proposed a framework for calculating the sediment exchange in two layers. On the basis of the conventional approaches, we derived a two-layer fine sediment sorting, which considers the transportation of fine sediment in the form of infiltration into the void spaces of the gravel-bed. The relationship between the fine sediment exchange and the affected factors was obtained by using the discrete element method (DEM) in combination with feedforward neural networks (FNN). The DEM model was validated and applied for gravel-bed flumes with different sizes of fine sediments. Further, we developed algorithms for extracting information in terms of gravel-bed packing, grain size distribution, and porosity variation. On the basis of the DEM results with this extracted information, we developed an FNN model for fine sediment sorting. Analyzing the calculated results and comparing them with the available measurements showed that our framework can successfully simulate the exchange of fine sediment in gravel-bed rivers.

scholarly journals Characterization of artisanal fisheries in Nepal and potential implications for the conservation and management of Ganges River Dolphin (Platanista gangetica gangetica)

2015 ◽  
Author(s):  
Shambhu Paudel ◽  
Juan C Levesque ◽  
Camilo Saavedra ◽  
Cristina Pita ◽  
Prabhat Pal
Keyword(s):  
Anthropogenic Activities ◽  
Fishing Effort ◽  
Main Channel ◽  
Artisanal Fisheries ◽  
Ganges River ◽  
River Systems ◽  
River Dolphin ◽  
Main River ◽  
Local Species ◽  
The Ganges

The Ganges River dolphin (Platanista gangetica gangetica) (GRD) is classified as one of the most endangered of all cetaceans in the world and the second scarcest freshwater cetacean. The population is estimated to be less than 2,000 individuals. In Nepal’s Narayani, Sapta Koshi, and Karnali river systems, survival of GRD continues to be threatened by various anthropogenic activities, such as dam construction and interactions with artisanal fisheries. A basic description of the geographic scope, economics, and types of gear used in these fisheries would help managers understand the fishery-dolphin interaction conflict and assist with developing potential solutions to reduce interactions between GRD and local fisheries in Nepal. The main purpose of the study was to collect fishery and socio-economic information by conducting interviews with local fishermen in the Narayani, Sapta Koshi, and Karnali river systems. Based on interviews (n = 163), 79 percent of Nepalese fishermen indicated fishing for local species (e.g., mullet [Rhinomugil corsula] or siloroid catfish [Bagarius bagarius]) was their primary form of income. Fishermen reported fishing effort was greater in summer than winter; greatest in the afternoon (1430 hrs ± 0.27) and during low water level conditions; and gear was set 4.8 ± 0.2 days/week. Fishermen reported using eight different types of monofilament nets (gillnets and cast nets). Sixty percent used gillnets less than 10 m long, and less than one third preferred gillnets between 10 and 100 m long; a few used gillnets longer than 100 m. Fishermen usually set their gear close to their village, and about 50 percent preferred to fish in tributaries followed by the main channel behind sandbars and islands, and the main channel near a bank. Fishermen reported seeing more GRD in the main river stem in winter. In summer, fishermen spotted more GRD in tributaries. Most fishermen told us they believed education, awareness, and changing occupations were important for GRD conservation, but they indicated that occupational options were currently limited in Nepal. Nepalese fishermen acknowledged that fisheries posed a risk to GRD, but they believed water pollution, and dam/irrigation development were the greatest threats.

scholarly journals Hydrologiczne uwarunkowania morfogenezy wybranych erozyjnych form rzeźby równi zalewowej na przykładzie doliny Bugu

2018 ◽  
Vol 27 (1) ◽  
pp. 57-70
Author(s):  
Piotr Ostrowski ◽  
Marta Utratna
Keyword(s):  
Flow Direction ◽  
Main Channel ◽  
River Valley ◽  
Oxbow Lakes ◽  
Hydrological Conditions ◽  
Ice Storms ◽  
Overbank Flow ◽  
The Relationship

The aim of the study was to analyze the relationship between hydrological conditions and morphogenesis of erosional landforms on the floodplain of the Bug river valley. It was found that forms such as side arms and oxbow lakes as a result of cyclical floods are subject to secondary erosion. The main reason for this phenomenon is the fact that they combine strings of overbank flow direction. In the case of ice storms, these forms take on the role of the main channel limiting the effects of floods.

scholarly journals Hazards due to large wood accumulations: Local scour and backwater rise

2018 ◽  
Vol 40 ◽  
pp. 02003 ◽  
Author(s):  
Isabella Schalko ◽  
Lukas Schmocker ◽  
Volker Weitbrecht ◽  
Robert M. Boes
Keyword(s):  
Shear Stress ◽  
Flood Hazard ◽  
Local Scour ◽  
Bridge Piers ◽  
Bed Shear Stress ◽  
Large Wood ◽  
Flume Experiments ◽  
Governing Parameter ◽  
Bed Material ◽  
Movable Bed

Large wood (LW) in rivers increases the flow variability and provides habitats for various species. During flood events, transported logs can accumulate at river infrastructures and increase the flood hazard. LW accumulations result in an upstream backwater rise and may increase local scour, for instance at bridge piers. Consequently, estimates of the resulting backwater rise and local scour are necessary to improve the flood hazard assessment. This study presents the findings of flume experiments with a movable bed on local scour and backwater rise due to LW accumulations. The approach flow conditions and the bed material were varied systematically for a specific LW accumulation volume. For all experiments, the initial condition for the bed material was defined as weak transport, since the bed shear stress was slightly below the critical bed shear stress for incipient motion. The inflow Froude number was identified as the governing parameter for backwater rise due to LW accumulations. The present study confirms the hypothesis that the resulting local scour reduces backwater rise. For the local scour, the unit discharge and the grain size diameter are the decisive parameters.

Comprehensive Research and Outlook of Loose Solid Materials on the Gully System under Hydrodynamic Conditions

2012 ◽  
Vol 212-213 ◽  
pp. 40-45 ◽  
Author(s):  
Shun Yang ◽  
Guo Qiang Ou ◽  
Xian Jun Ji ◽  
Jun Wang
Keyword(s):  
Debris Flow ◽  
Hydrodynamic Effect ◽  
Initial Condition ◽  
Hydrodynamic Conditions ◽  
Slope Surface ◽  
Flume Experiments ◽  
Solid Materials ◽  
Flow Process ◽  
Artificial Rainfall ◽  
The Relationship

The paper reviewed the research and progress of solid materials on the gully system in the world and pointed out the shortage of it. On the condition of hydrodynamics, many papers available concentrated on the relationship between rainfall parameters and debris flow occurrence, rainfall infiltration and surface runoff; while on the solid materials on the gully or slope surface, a lot of researches focused on the flume experiments to analyses the initial condition and debris flow process under hydrodynamic effect together with artificial rainfall. Base on the reviews previous, paper give some prospects of research under hydrodynamic conditions in the futures.

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