The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
P. Breil - One of the best experts on this subject based on the ideXlab platform.
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Test of three methods to detect the Overbank Flow from water level time-series analysis
Hydrological Processes, 2010Co-Authors: O. Navratil, M.b. Albert, P. BreilAbstract:In this study, we propose to identify morphological and hydraulic characteristics related to Overbank Flows in the water level time-series available at many gauged stations. The results obtained at 13 river stations (the catchment sizes vary from 10 to 1700 km2 with contrasted geology, land use and rainfalls regime) show that overFlow mechanisms at the river-reach scale can be systematically identified in the water level frequency distribution estimated with the peaks-over-threshold (POT) method. A first level (Lts1) was in the range of the incipient flooding onto the floodplain. Even if the definition of this level is variable in terms of flooded area at the reach scale, this method can be useful in providing a first estimation of the bankfull level for many gauged stations, without complex and costly field surveys. A second level (Lts2) was systematically detected on average 38 cm above the topographic flat floodplain elevation. The Lts2 inflection in the water-level frequency distribution is assumed to reflect a composite effect of catchment hydrology and local hydraulics and channel geometry, without possibility to make a clear distinction between both processes at the moment. The local or reach scale effect would probably play an essential role in the frequency distribution as flood attenuation at catchment scale may explain the inflection Lts2 at only three sites. In light of the knowledge acquired in laboratory flumes with compound channels, most of the time Lts2 level would correspond to the level of resumption of Flow both in the main channel and the floodplain. Once this method is validated in various physiographic contexts, it should apply to many hydrometric stations for both synchronic (e.g. regional analysis) and diachronic analysis (e.g. evolution over time of the bankfull discharge) to evaluate anthropic impacts on river morphology. Copyright © 2010 John Wiley & Sons, Ltd.
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Test of three methods to detect the Overbank Flow from water level time-series analysis
Hydrological Processes, 2010Co-Authors: O. Navratil, M.b. Albert, P. BreilAbstract:International audienceIn this study, we propose to identify morphological and hydraulic characteristics related to Overbank Flows in the water level time-series available at many gauged stations. The results obtained at 13 river stations (the catchment sizes vary from 10 to 1700 km2 with contrasted geology, land use and rainfalls regime) show that overFlow mechanisms at the river-reach scale can be systematically identified in the water level frequency distribution estimated with the peaks-over-threshold (POT) method. A first level (Lts1) was in the range of the incipient flooding onto the floodplain. Even if the definition of this level is variable in terms of flooded area at the reach scale, this method can be useful in providing a first estimation of the bankfull level for many gauged stations, without complex and costly field surveys. A second level (Lts2) was systematically detected on average 38 cm above the topographic flat floodplain elevation. The Lts2 inflection in the water-level frequency distribution is assumed to reflect a composite effect of catchment hydrology and local hydraulics and channel geometry, without possibility to make a clear distinction between both processes at the moment. The local or reach scale effect would probably play an essential role in the frequency distribution as flood attenuation at catchment scale may explain the inflection Lts2 at only three sites. In light of the knowledge acquired in laboratory flumes with compound channels, most of the time Lts2 level would correspond to the level of resumption of Flow both in the main channel and the floodplain. Once this method is validated in various physiographic contexts, it should apply to many hydrometric stations for both synchronic (e.g. regional analysis) and diachronic analysis (e.g. evolution over time of the bankfull discharge) to evaluate anthropic impacts on river morphology. Copyright © 2010 John Wiley & Sons, Ltd
José-miguel Sanchez-pérez - One of the best experts on this subject based on the ideXlab platform.
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Spatially distributed modelling of surface water-groundwater exchanges during Overbank flood events – a case study at the Garonne River
Advances in Water Resources, 2016Co-Authors: Léonard Bernard-jannin, David Brito, Xiaoling Sun, Eduardo Jauch, Ramiro Neves, Sabine Sauvage, José-miguel Sanchez-pérezAbstract:Exchanges between surface water (SW) and groundwater (GW) are of considerable importance to flood- plain ecosystems and biogeochemical cycles. Flood events in particular are important for riparian water budget and element exchanges and processing. However SW-GW exchanges present complex spatial and temporal patterns and modelling can provide useful knowledge about the processes involved at the scale of the reach and its adjacent floodplain. This study used a physically-based, spatially-distributed mod- elling approach for studying SW-GW exchanges. The modelling in this study is based on the MOHID Land model, combining the modelling of surface water Flow in 2D with the Saint-Venant equation and the modelling of unsaturated groundwater Flow in 3D with the Richards’ equation. Overbank Flow dur- ing floods was also integrated, as well as water exchanges between the two domains across the entire floodplain. Conservative transport simulations were also performed to study and validate the simulation of the mixing between surface water and groundwater. The model was applied to the well-monitored study site of Monbéqui (6.6 km ²) in the Garonne floodplain (south-west France) for a five-month period and was able to represent the hydrology of the study area. Infiltration (SW to GW) and exfiltration (SW to GW) were characterised over the five-month period. Results showed that infiltration and exfiltration exhibited strong spatiotemporal variations, and infiltration from Overbank Flow accounted for 88% of the total simulated infiltration, corresponding to large flood periods. The results confirmed that Overbank flood events played a determinant role in floodplain water budget and SW-GW exchanges compared to smaller (below bankfull) flood events. The impact of floods on water budget appeared to be similar for flood events exceeding a threshold corresponding to the five-year return period event due to the study area’s topography. Simulation of Overbank Flow during flood events was an important feature in the ac- curate assessment of exchanges between surface water and groundwater in floodplain areas, especially when considering large flood events.
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Spatially distributed modelling of surface water-groundwater exchanges during Overbank flood events – a case study at the Garonne River
Advances in Water Resources, 2016Co-Authors: Léonard Bernard-jannin, David Brito, Xiaoling Sun, Eduardo Jauch, Ramiro Neves, Sabine Sauvage, José-miguel Sanchez-pérezAbstract:Exchanges between surface water (SW) and groundwater (GW) are of considerable importance to flood- plain ecosystems and biogeochemical cycles. Flood events in particular are important for riparian water budget and element exchanges and processing. However SW-GW exchanges present complex spatial and temporal patterns and modelling can provide useful knowledge about the processes involved at the scale of the reach and its adjacent floodplain. This study used a physically-based, spatially-distributed mod- elling approach for studying SW-GW exchanges. The modelling in this study is based on the MOHID Land model, combining the modelling of surface water Flow in 2D with the Saint-Venant equation and the modelling of unsaturated groundwater Flow in 3D with the Richards’ equation. Overbank Flow dur- ing floods was also integrated, as well as water exchanges between the two domains across the entire floodplain. Conservative transport simulations were also performed to study and validate the simulation of the mixing between surface water and groundwater. The model was applied to the well-monitored study site of Monbequi (6.6 km ²) in the Garonne floodplain (south-west France) for a five-month period and was able to represent the hydrology of the study area. Infiltration (SW to GW) and exfiltration (SW to GW) were characterised over the five-month period. Results showed that infiltration and exfiltration exhibited strong spatiotemporal variations, and infiltration from Overbank Flow accounted for 88% of the total simulated infiltration, corresponding to large flood periods. The results confirmed that Overbank flood events played a determinant role in floodplain water budget and SW-GW exchanges compared to smaller (below bankfull) flood events. The impact of floods on water budget appeared to be similar for flood events exceeding a threshold corresponding to the five-year return period event due to the study area’s topography. Simulation of Overbank Flow during flood events was an important feature in the ac- curate assessment of exchanges between surface water and groundwater in floodplain areas, especially when considering large flood events.
O. Navratil - One of the best experts on this subject based on the ideXlab platform.
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Test of three methods to detect the Overbank Flow from water level time-series analysis
Hydrological Processes, 2010Co-Authors: O. Navratil, M.b. Albert, P. BreilAbstract:In this study, we propose to identify morphological and hydraulic characteristics related to Overbank Flows in the water level time-series available at many gauged stations. The results obtained at 13 river stations (the catchment sizes vary from 10 to 1700 km2 with contrasted geology, land use and rainfalls regime) show that overFlow mechanisms at the river-reach scale can be systematically identified in the water level frequency distribution estimated with the peaks-over-threshold (POT) method. A first level (Lts1) was in the range of the incipient flooding onto the floodplain. Even if the definition of this level is variable in terms of flooded area at the reach scale, this method can be useful in providing a first estimation of the bankfull level for many gauged stations, without complex and costly field surveys. A second level (Lts2) was systematically detected on average 38 cm above the topographic flat floodplain elevation. The Lts2 inflection in the water-level frequency distribution is assumed to reflect a composite effect of catchment hydrology and local hydraulics and channel geometry, without possibility to make a clear distinction between both processes at the moment. The local or reach scale effect would probably play an essential role in the frequency distribution as flood attenuation at catchment scale may explain the inflection Lts2 at only three sites. In light of the knowledge acquired in laboratory flumes with compound channels, most of the time Lts2 level would correspond to the level of resumption of Flow both in the main channel and the floodplain. Once this method is validated in various physiographic contexts, it should apply to many hydrometric stations for both synchronic (e.g. regional analysis) and diachronic analysis (e.g. evolution over time of the bankfull discharge) to evaluate anthropic impacts on river morphology. Copyright © 2010 John Wiley & Sons, Ltd.
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Test of three methods to detect the Overbank Flow from water level time-series analysis
Hydrological Processes, 2010Co-Authors: O. Navratil, M.b. Albert, P. BreilAbstract:International audienceIn this study, we propose to identify morphological and hydraulic characteristics related to Overbank Flows in the water level time-series available at many gauged stations. The results obtained at 13 river stations (the catchment sizes vary from 10 to 1700 km2 with contrasted geology, land use and rainfalls regime) show that overFlow mechanisms at the river-reach scale can be systematically identified in the water level frequency distribution estimated with the peaks-over-threshold (POT) method. A first level (Lts1) was in the range of the incipient flooding onto the floodplain. Even if the definition of this level is variable in terms of flooded area at the reach scale, this method can be useful in providing a first estimation of the bankfull level for many gauged stations, without complex and costly field surveys. A second level (Lts2) was systematically detected on average 38 cm above the topographic flat floodplain elevation. The Lts2 inflection in the water-level frequency distribution is assumed to reflect a composite effect of catchment hydrology and local hydraulics and channel geometry, without possibility to make a clear distinction between both processes at the moment. The local or reach scale effect would probably play an essential role in the frequency distribution as flood attenuation at catchment scale may explain the inflection Lts2 at only three sites. In light of the knowledge acquired in laboratory flumes with compound channels, most of the time Lts2 level would correspond to the level of resumption of Flow both in the main channel and the floodplain. Once this method is validated in various physiographic contexts, it should apply to many hydrometric stations for both synchronic (e.g. regional analysis) and diachronic analysis (e.g. evolution over time of the bankfull discharge) to evaluate anthropic impacts on river morphology. Copyright © 2010 John Wiley & Sons, Ltd
Léonard Bernard-jannin - One of the best experts on this subject based on the ideXlab platform.
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Spatially distributed modelling of surface water-groundwater exchanges during Overbank flood events – a case study at the Garonne River
Advances in Water Resources, 2016Co-Authors: Léonard Bernard-jannin, David Brito, Xiaoling Sun, Eduardo Jauch, Ramiro Neves, Sabine Sauvage, José-miguel Sanchez-pérezAbstract:Exchanges between surface water (SW) and groundwater (GW) are of considerable importance to flood- plain ecosystems and biogeochemical cycles. Flood events in particular are important for riparian water budget and element exchanges and processing. However SW-GW exchanges present complex spatial and temporal patterns and modelling can provide useful knowledge about the processes involved at the scale of the reach and its adjacent floodplain. This study used a physically-based, spatially-distributed mod- elling approach for studying SW-GW exchanges. The modelling in this study is based on the MOHID Land model, combining the modelling of surface water Flow in 2D with the Saint-Venant equation and the modelling of unsaturated groundwater Flow in 3D with the Richards’ equation. Overbank Flow dur- ing floods was also integrated, as well as water exchanges between the two domains across the entire floodplain. Conservative transport simulations were also performed to study and validate the simulation of the mixing between surface water and groundwater. The model was applied to the well-monitored study site of Monbéqui (6.6 km ²) in the Garonne floodplain (south-west France) for a five-month period and was able to represent the hydrology of the study area. Infiltration (SW to GW) and exfiltration (SW to GW) were characterised over the five-month period. Results showed that infiltration and exfiltration exhibited strong spatiotemporal variations, and infiltration from Overbank Flow accounted for 88% of the total simulated infiltration, corresponding to large flood periods. The results confirmed that Overbank flood events played a determinant role in floodplain water budget and SW-GW exchanges compared to smaller (below bankfull) flood events. The impact of floods on water budget appeared to be similar for flood events exceeding a threshold corresponding to the five-year return period event due to the study area’s topography. Simulation of Overbank Flow during flood events was an important feature in the ac- curate assessment of exchanges between surface water and groundwater in floodplain areas, especially when considering large flood events.
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Spatially distributed modelling of surface water-groundwater exchanges during Overbank flood events – a case study at the Garonne River
Advances in Water Resources, 2016Co-Authors: Léonard Bernard-jannin, David Brito, Xiaoling Sun, Eduardo Jauch, Ramiro Neves, Sabine Sauvage, José-miguel Sanchez-pérezAbstract:Exchanges between surface water (SW) and groundwater (GW) are of considerable importance to flood- plain ecosystems and biogeochemical cycles. Flood events in particular are important for riparian water budget and element exchanges and processing. However SW-GW exchanges present complex spatial and temporal patterns and modelling can provide useful knowledge about the processes involved at the scale of the reach and its adjacent floodplain. This study used a physically-based, spatially-distributed mod- elling approach for studying SW-GW exchanges. The modelling in this study is based on the MOHID Land model, combining the modelling of surface water Flow in 2D with the Saint-Venant equation and the modelling of unsaturated groundwater Flow in 3D with the Richards’ equation. Overbank Flow dur- ing floods was also integrated, as well as water exchanges between the two domains across the entire floodplain. Conservative transport simulations were also performed to study and validate the simulation of the mixing between surface water and groundwater. The model was applied to the well-monitored study site of Monbequi (6.6 km ²) in the Garonne floodplain (south-west France) for a five-month period and was able to represent the hydrology of the study area. Infiltration (SW to GW) and exfiltration (SW to GW) were characterised over the five-month period. Results showed that infiltration and exfiltration exhibited strong spatiotemporal variations, and infiltration from Overbank Flow accounted for 88% of the total simulated infiltration, corresponding to large flood periods. The results confirmed that Overbank flood events played a determinant role in floodplain water budget and SW-GW exchanges compared to smaller (below bankfull) flood events. The impact of floods on water budget appeared to be similar for flood events exceeding a threshold corresponding to the five-year return period event due to the study area’s topography. Simulation of Overbank Flow during flood events was an important feature in the ac- curate assessment of exchanges between surface water and groundwater in floodplain areas, especially when considering large flood events.
Koji Shiono - One of the best experts on this subject based on the ideXlab platform.
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Modelling of Overbank Flow structures in meandering channels
2011Co-Authors: Ponnambalam Rameshwaran, Koji ShionoAbstract:Overbank Flow in a meandering channel displays a complex coherent Flow structure resulting from the interplay between the floodplain and main channel Flows. Understanding and modeling such coherent Flow structure are of great importance for addressing river engineering and management issues where the design solutions are required to retain natural channel features and to maintain a balance between environmental, ecological and amenity issues. In recent years, numerical models have increasingly been used for river Flow modeling in order to understand their Flow behavior. The main aim of this paper is to predict and investigate the Overbank Flow behavior in the physical model of meandering channels using three-dimensional (3D) numerical model. The performance of the model is first assessed by comparing predicted results with the limited experimental data. The experiment data were obtained from a 1:5 scale physical model of the River Blackwater and a flume study in Loughborough University. The predicted distributions of the streamwise velocity, secondary vectors, turbulent parameters and bed shear stress are used to investigate the coherent Flow structures along the channel, in both the horizontal and inclined floodplain cases and main channel mobile sand bed case. The results show that the three-dimensional model predicts the coherent Flow structures reasonably well.
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The effect of floodplain roughness on Flow structures, bedforms and sediment transport rates in meandering channels with Overbank Flows: Part I
Journal of Hydraulic Research, 2009Co-Authors: Koji Shiono, Jake Spooner, Ponnambalam Rameshwaran, Tony L. Chan, Jim H. ChandlerAbstract:Studies were carried out to understand the effect of floodplain roughness on Flow structures, sediment transport rates and bedforms in a mobile meandering channel with Overbank Flows. Three floodplain roughnesses were examined in this study. Flow structures and bedforms were measured using a three component laser Doppler anemometer (LDA) system and digital photogrammetry, respectively. Comparisons of Flow structures and bedforms between different floodplain rougheness are made. Considerable changes in the Flow structure and bed form were observed. In particular, multiple secondary Flow cells along the meandering channel occur at deeper water depths as the floodplain roughness increases. These cells also cause a series of wavy bedforms along the meandering channel. This paper is separated into two parts. Part I concentrates, in detail, on the Flow structure with bedforms in the meandering channel for Overbank Flow as to change of floodplain roughness. The sister paper, Part II, concentrates on bed form for...
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Flow characteristics in meandering channels with non-mobile and mobile beds for Overbank Flows
Journal of Hydraulic Research, 2008Co-Authors: Koji Shiono, Jake Spooner, Ponnambalam Rameshwaran, Tony L. Chan, Jim H. ChandlerAbstract:Experiments were conducted in meandering channels with non-mobile and mobile beds to measure Flow rates, velocities, turbulent kinetic energies, bedforms and sediment transport rates for Overbank Flows. The behaviour of bedform in meandering channels with Overbank Flows was observed using digital photogrammetry, with velocity measurements taken with a Laser Doppler Anemometer. The bedform structure and velocity distributions along the meandering channel were obtained for bank full Flow and three Overbank Flow depths. Important interactions between the Flow structure and bedform were observed along the meandering channel. The sediment transport rates collected during the experiment showed three phases; an increase in the sediment transport rate up to the bankfull level, a small decrease as the Flow goes Overbank up to a relative depth ratio of 0.3 and then an increase again for higher Flow depths. The regions of higher turbulent kinetic energy were identified. The total energy losses due to friction, secon...
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Modelling of meandering channels for Overbank Flow
Proceedings of the Institution of Civil Engineers - Water and Maritime Engineering, 2003Co-Authors: Jake Spooner, Koji ShionoAbstract:The depth-averaged equation of motion in the stream-wise direction with curvilinear coordinates was considered. Its application to a meandering channel for over-bank Flow was investigated using velocity and boundary shear stress. The velocity and boundary shear stress were measured using a laser Doppler anemometer and Preston tube respectively. The advection and bed friction terms in the equation of motion were found to be significant, but the transverse turbulence was found to be insignificant at the apex section. As a result the equation of motion was considerably simplified. The calibrating advection term with the data gave two equations. These gave a good prediction of velocity across the apex section for different scales of meandering channels. The investigation of the advection term with varying scaled flume data suggested that it is important for a small flume, but tends to be less significant in a large flume.
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Computer modelling of two-stage meandering channel Flows
Proceedings of the Institution of Civil Engineers - Water and Maritime Engineering, 2003Co-Authors: Ponnambalam Rameshwaran, Koji ShionoAbstract:Prediction of Flow in two-stage meandering channels for Overbank Flow was undertaken using a commercially available computer model. The software, TELEMAC-2D, solves the depth-averaged Navier–Stokes equations with non-structured grids for free surface Flow. The model results are compared with the experimental data obtained from the UK Flood Channel Facility. Advection schemes offered in TELEMAC-2D are examined for their influence upon a bed friction coefficient. The effect of mesh resolution on solution accuracy is also investigated. The simulated distributions of depth-averaged velocity and boundary shear stress are also used to investigate the accuracy of the TELEMAC-2D prediction by comparison with the experimental data. The 1D and local Manning coefficients calculated using the experimental data are compared with the calibrated Manning coefficient. The results show that the choice of Manning coefficient is vital for an accurate prediction of Overbank Flow in two-stage meandering channels, and that tran...
