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Jonathan W F Remo - One of the best experts on this subject based on the ideXlab platform.
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climatic control of mississippi River flood hazard amplified by River Engineering
Nature, 2018Co-Authors: Jonathan W F Remo, Samuel E Munoz, Liviu Giosan, Matthew D Therrell, Zhixiong Shen, Richard M Sullivan, C WimanAbstract:Over the past century, many of the world's major Rivers have been modified for the purposes of flood mitigation, power generation and commercial navigation. Engineering modifications to the Mississippi River system have altered the River's sediment levels and channel morphology, but the influence of these modifications on flood hazard is debated. Detecting and attributing changes in River discharge is challenging because instrumental streamflow records are often too short to evaluate the range of natural hydrological variability before the establishment of flood mitigation infrastructure. Here we show that multi-decadal trends of flood hazard on the lower Mississippi River are strongly modulated by dynamical modes of climate variability, particularly the El Nino-Southern Oscillation and the Atlantic Multidecadal Oscillation, but that the artificial channelization (confinement to a straightened channel) has greatly amplified flood magnitudes over the past century. Our results, based on a multi-proxy reconstruction of flood frequency and magnitude spanning the past 500 years, reveal that the magnitude of the 100-year flood (a flood with a 1 per cent chance of being exceeded in any year) has increased by 20 per cent over those five centuries, with about 75 per cent of this increase attributed to River Engineering. We conclude that the interaction of human alterations to the Mississippi River system with dynamical modes of climate variability has elevated the current flood hazard to levels that are unprecedented within the past five centuries.
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climatic control of mississippi River flood hazard amplified by River Engineering
Nature, 2018Co-Authors: Jonathan W F Remo, Samuel E Munoz, Liviu Giosan, Matthew D Therrell, Zhixiong Shen, Richard M Sullivan, C WimanAbstract:A suite of River discharge, tree-ring, sedimentary and climate data shows that the Mississippi’s flood magnitude has risen by about twenty per cent over the past half-century, largely owing to Engineering works. Instrumental records of River discharge do not go far enough back in time to place recent flood activity in a longer-term context, making it difficult to understand how climate variability and human activity might have affected flooding. Now, Samuel Munoz and colleagues reconstruct the past flood frequency of the Mississippi River from a compilation of River-discharge, tree-ring, sedimentary and climate data. The results show that the magnitude of the 100-year flood has gone up by about 20 per cent over the past 500 years. Climate cycles account for most of the variability in flooding on multidecadal timescales, but Engineering works account for about three-quarters of the long-term increase. Over the past century, many of the world’s major Rivers have been modified for the purposes of flood mitigation, power generation and commercial navigation1. Engineering modifications to the Mississippi River system have altered the River’s sediment levels and channel morphology2, but the influence of these modifications on flood hazard is debated3,4,5. Detecting and attributing changes in River discharge is challenging because instrumental streamflow records are often too short to evaluate the range of natural hydrological variability before the establishment of flood mitigation infrastructure. Here we show that multi-decadal trends of flood hazard on the lower Mississippi River are strongly modulated by dynamical modes of climate variability, particularly the El Nino–Southern Oscillation and the Atlantic Multidecadal Oscillation, but that the artificial channelization (confinement to a straightened channel) has greatly amplified flood magnitudes over the past century. Our results, based on a multi-proxy reconstruction of flood frequency and magnitude spanning the past 500 years, reveal that the magnitude of the 100-year flood (a flood with a 1 per cent chance of being exceeded in any year) has increased by 20 per cent over those five centuries, with about 75 per cent of this increase attributed to River Engineering. We conclude that the interaction of human alterations to the Mississippi River system with dynamical modes of climate variability has elevated the current flood hazard to levels that are unprecedented within the past five centuries.
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the use of retro and scenario modeling to assess effects of 100 years River of Engineering and land cover change on middle and lower mississippi River flood stages
Journal of Hydrology, 2009Co-Authors: Jonathan W F Remo, Nicholas Pinter, Reuben A. HeineAbstract:Summary Since the 19th century, the Middle and Lower Mississippi River (MMR and LMR) have been intensively modified for flood protection and commercial navigation. In order to quantify the effects of levee expansion, channel modification, and land-cover change upon flood stages, we have developed 1-D unsteady-flow models of multiple historical reference conditions (“retro-models”) for three large study reaches (225–315 km each): one along the MMR and two reaches along the LMR. For each reference condition, four 1-D unsteady-flow models were developed. These models include a calibrated model of actual conditions and three “scenario” models: (1) a model with levees of the next time step, (2) a model with the channel geometry of the next time step, and (3) a model with floodplain roughness (i.e., land cover) of the next time step. Comparison of the model for actual conditions and the scenario models provide a quantitative assessment of levee expansion, channel modification, and land-cover change on stage. Scenario modeling suggests that the majority (38–70%) of the changes in flood stage on the LMR and MMR study reaches can be attributed to changes in channel geometry and hydraulic roughness. Levees were the next largest contributor to changes in flood stage. For time steps with significant levee expansion, these structures increase stage up to 1.0 m. Observed changes in floodplain land cover were associated with little (or none) of the increase in flood stage. These result show changes in channel geometry and roughness related to River Engineering tools employed for improving navigation and flood protection are the principal dRivers of historic changes in flood stages along these investigated reaches.
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cumulative impacts of River Engineering mississippi and lower missouri Rivers
River Research and Applications, 2009Co-Authors: Nicholas Pinter, Abebe A. Jemberie, Jonathan W F Remo, Reuben A. Heine, Brian S. IckesAbstract:The goal of this study was to construct a large, data-rich model to test hydrological responses to Engineering modifications on over 3200 km of the Mississippi and Lower Missouri Rivers. We compiled model explanatory variables from a geospatial database quantifying construction of all bridges, wing dikes, bendway weirs, levees, artificial meander cutoffs, channel constriction and navigational dams over the past 100-150 years. Response variables were derived from 68 rated and un-rated hydrologic stations in the study area, with responses analysed across a range of discharges from within-channel flows up to moderate floods. Correlation analysis, multiple linear regression and stepwise regression analyses document strong and consistent responses to construction history, both in individual reach-scale models and systemwide. Meander cutoffs are associated with degradation and acceleration of flow that has reduced stages across the full discharge range. Navigational dams on the Upper Mississippi River increased low-flow stages and flood levels to a lesser extent, with little or no post-dam change. One of the strongest signals was the hydrologic response to wing-dike construction, which resulted in large back-water increases in stage upstream of wing dikes and mixed effects downstream, including the overlapping effects of incision and velocity losses. Levees were associated with local flow concentration, overbank storage loss and floodplain conveyance loss depending on reach-scale conditions. The results presented here (1) quantify incremental and cumulative hydrologic responses to a range of Engineering activities and (2) provide an empirical tool for verifying and assessing hydraulic and other models of River-system change. Copyright © 2009 John Wiley & Sons, Ltd.
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Flood trends and River Engineering on the Mississippi River system
Geophysical Research Letters, 2008Co-Authors: Nicholas Pinter, Abebe A. Jemberie, Jonathan W F Remo, Reuben A. Heine, Brian S. IckesAbstract:Along >4000 km of the Mississippi River system, we document that climate, land-use change, and River Engineering have contributed to statistically significant increases in flooding over the past 100–150 years. Trends were tested using a database of >8 million hydrological measurements. A geospatial database of historical Engineering construction was used to quantify the response of flood levels to each unit of Engineering infrastructure. Significant climate- and/or land use-driven increases in flow were detected, but the largest and most pervasive contributors to increased flooding on the Mississippi River system were wing dikes and related navigational structures, followed by progressive levee construction. In the area of the 2008 Upper Mississippi flood, for example, about 2 m of the flood crest is linked to navigational and flood-control Engineering. Systemwide, large increases in flood levels were documented at locations and at times of wing-dike and levee construction.
Nicholas Pinter - One of the best experts on this subject based on the ideXlab platform.
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the use of retro and scenario modeling to assess effects of 100 years River of Engineering and land cover change on middle and lower mississippi River flood stages
Journal of Hydrology, 2009Co-Authors: Jonathan W F Remo, Nicholas Pinter, Reuben A. HeineAbstract:Summary Since the 19th century, the Middle and Lower Mississippi River (MMR and LMR) have been intensively modified for flood protection and commercial navigation. In order to quantify the effects of levee expansion, channel modification, and land-cover change upon flood stages, we have developed 1-D unsteady-flow models of multiple historical reference conditions (“retro-models”) for three large study reaches (225–315 km each): one along the MMR and two reaches along the LMR. For each reference condition, four 1-D unsteady-flow models were developed. These models include a calibrated model of actual conditions and three “scenario” models: (1) a model with levees of the next time step, (2) a model with the channel geometry of the next time step, and (3) a model with floodplain roughness (i.e., land cover) of the next time step. Comparison of the model for actual conditions and the scenario models provide a quantitative assessment of levee expansion, channel modification, and land-cover change on stage. Scenario modeling suggests that the majority (38–70%) of the changes in flood stage on the LMR and MMR study reaches can be attributed to changes in channel geometry and hydraulic roughness. Levees were the next largest contributor to changes in flood stage. For time steps with significant levee expansion, these structures increase stage up to 1.0 m. Observed changes in floodplain land cover were associated with little (or none) of the increase in flood stage. These result show changes in channel geometry and roughness related to River Engineering tools employed for improving navigation and flood protection are the principal dRivers of historic changes in flood stages along these investigated reaches.
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cumulative impacts of River Engineering mississippi and lower missouri Rivers
River Research and Applications, 2009Co-Authors: Nicholas Pinter, Abebe A. Jemberie, Jonathan W F Remo, Reuben A. Heine, Brian S. IckesAbstract:The goal of this study was to construct a large, data-rich model to test hydrological responses to Engineering modifications on over 3200 km of the Mississippi and Lower Missouri Rivers. We compiled model explanatory variables from a geospatial database quantifying construction of all bridges, wing dikes, bendway weirs, levees, artificial meander cutoffs, channel constriction and navigational dams over the past 100-150 years. Response variables were derived from 68 rated and un-rated hydrologic stations in the study area, with responses analysed across a range of discharges from within-channel flows up to moderate floods. Correlation analysis, multiple linear regression and stepwise regression analyses document strong and consistent responses to construction history, both in individual reach-scale models and systemwide. Meander cutoffs are associated with degradation and acceleration of flow that has reduced stages across the full discharge range. Navigational dams on the Upper Mississippi River increased low-flow stages and flood levels to a lesser extent, with little or no post-dam change. One of the strongest signals was the hydrologic response to wing-dike construction, which resulted in large back-water increases in stage upstream of wing dikes and mixed effects downstream, including the overlapping effects of incision and velocity losses. Levees were associated with local flow concentration, overbank storage loss and floodplain conveyance loss depending on reach-scale conditions. The results presented here (1) quantify incremental and cumulative hydrologic responses to a range of Engineering activities and (2) provide an empirical tool for verifying and assessing hydraulic and other models of River-system change. Copyright © 2009 John Wiley & Sons, Ltd.
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Flood trends and River Engineering on the Mississippi River system
Geophysical Research Letters, 2008Co-Authors: Nicholas Pinter, Abebe A. Jemberie, Jonathan W F Remo, Reuben A. Heine, Brian S. IckesAbstract:Along >4000 km of the Mississippi River system, we document that climate, land-use change, and River Engineering have contributed to statistically significant increases in flooding over the past 100–150 years. Trends were tested using a database of >8 million hydrological measurements. A geospatial database of historical Engineering construction was used to quantify the response of flood levels to each unit of Engineering infrastructure. Significant climate- and/or land use-driven increases in flow were detected, but the largest and most pervasive contributors to increased flooding on the Mississippi River system were wing dikes and related navigational structures, followed by progressive levee construction. In the area of the 2008 Upper Mississippi flood, for example, about 2 m of the flood crest is linked to navigational and flood-control Engineering. Systemwide, large increases in flood levels were documented at locations and at times of wing-dike and levee construction.
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retro modeling the middle mississippi River
Journal of Hydrology, 2007Co-Authors: Jonathan W F Remo, Nicholas PinterAbstract:Summary A one-dimensional (1-D) unsteady-flow “retro-model” was developed using historic (c. 1900) hydrologic and geospatial data and implemented using HEC-RAS. The objective of this investigation was to create a 1-D unsteady-flow model for the Middle Mississippi River for the beginning of the 20th century in order to assess the magnitude and types of changes in flood stages associated with 20th century River Engineering. The retro-model was constructed from survey data dating to 1888–1889 and hydrologic data from 1900 to 1904. The late 19th century survey data was supplemented by a modern high-resolution DEM used to fill gaps in the historic data. Land-cover data recorded during this historic survey was used to establish floodplain roughness values based on published Manning’s n for the various land-cover types, and these roughness values were then adjusted to calibrate the model. Comparison of the retro-model results with the 2004 Upper Mississippi River System Flow Frequency Study (UMRSFFS) flood stages showed increases in flood stages of 2.3–4.7 m for large events (>50-year recurrence interval). These results confirm previous research results showing large-scale reductions in flood conveyance on the Middle Mississippi during the 20th century. Increased roughness of the floodway coupled with reduction in channel and floodplain area due to wing dike and levee construction are the likely explanation for the observed increases in flood stages. Between 1889 and 1998, channel widths through the study reach decreased ∼40%, and floodplain area for the 100-year flood decreased by ∼60%. In addition, Manning’s n values in the retro-model were lower than the values used in the UMRSFSS, suggesting that (1) the modern floodway is rougher than the historic floodway, (2) this increased roughness is not a result of explicit changes in land cover, but rather (3) the increase is a result of implicit roughness changes such as wing dike construction. The retro-model developed in this investigation provides a framework for modeling hydrodynamic and ecological responses to altered hydrologic regimes during more than a hundred years of channel modification.
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hydrodynamic and morphodynamic response to River Engineering documented by fixed discharge analysis lower missouri River usa
Journal of Hydrology, 2005Co-Authors: Nicholas Pinter, Reuben A. HeineAbstract:Abstract This research detects long-term trends in flow conveyance on the Lower Missouri River, and uses equal-discharge analysis of channel-gaging time series to assess the mechanisms driving these trends. Five long-term gaging stations along the Lower Missouri were examined using specific-gage analysis, which is a technique that holds discharge constant in order to observe trends in water-surface elevation (or stage) over time. This analysis reveals that for all flood conditions on the Lower Missouri River, stages have systematically risen for equal discharge volumes over the period of record. Flows that were fully contained within the Missouri channel in the early 20th century now create floods, and extreme high flows today are associated with stages as much as 3.7 m higher than at the start of the record. Equal-discharge analysis also can be used for analyzing time series of other parameters that co-vary strongly with discharge and that change systematically over time. On the Lower Missouri, long-term records of River gaging measurements, including cross-sectional area, flow velocity, and channel width, have been collected for the past ∼70 years. Equal-discharge analysis of these parameters illustrates the mechanisms of channel change driving flood magnification. At three stations, decreased flow velocity has been the dominant mechanism driving stage changes. At two other stations, constriction in channel cross-sectional area has increased flood stages. These changes in channel geometry and flow dynamics correlate with wing-dam construction and other Engineering of the Lower Missouri River, but the changes occur progressively over the duration of record as a gradual and reach-scale re-equilibration of the fluvial system. Magnification of flood stages should be recognized on the Missouri River and incorporated into current estimates of flood hazard and into strategies for River management and flood mitigation in the future.
Helmut Habersack - One of the best experts on this subject based on the ideXlab platform.
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insights into bedload transport processes of a large regulated gravel bed River
Earth Surface Processes and Landforms, 2018Co-Authors: Marcel Liedermann, Michael Tritthart, Philipp Gmeiner, Andrea Kreisler, Helmut HabersackAbstract:A comprehensive monitoring program focusing on bedload transport behaviour was conducted at a large gravel-bed River. Innovative monitoring strategies were developed during five years of preconstruction observations accompanying a restoration project. A bedload basket sampler was used to perform 55 cross-sectional measurements, which cover the entire water discharge spectrum from a 200-year flood event in 2013 to a rare low flow event. The monitoring activities provide essential knowledge regarding bedload transport processes in large Rivers. We have identified the initiation of motion under low flow conditions and a decrease in the rate of bedload discharge with increasing water discharge around bankfull conditions. Bedload flux strongly increases again during high flood events when the entire inundation area is flooded. No bedload hysteresis was observed. The effective discharge for bedload transport was determined to be near mean flow conditions, which is therefore at a lower flow discharge than expected. A numerical sediment transport model was able to reproduce the measured sediment transport patterns. The unique dataset enables the characterisation of bedload transport patterns in a large and regulated gravel-bed River, evaluation of modern River Engineering measures on the Danube, and, as a pilot project has recently been under construction, is able to address ongoing River bed incision, unsatisfying ecological conditions for the adjacent national park and insufficient water depths for inland navigation.
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Challenges of River basin management: Current status of, and prospects for, the River Danube from a River Engineering perspective.
Science of The Total Environment, 2015Co-Authors: Helmut Habersack, Adrian Stanica, Igor Liska, Raimund Mair, Elisabeth Jäger, Thomas Hein, Christoph Hauer, Chris BradleyAbstract:In the Danube River Basin multiple pressures affect the River system as a consequence of River Engineering works, altering both the River hydrodynamics and morphodynamics. The main objective of this paper is to identify the effects of hydropower development, flood protection and Engineering works for navigation on the Danube and to examine specific impacts of these developments on sediment transport and River morphology. Whereas impoundments are characterised by deposition and an excess of sediment with remobilisation of fine sediments during severe floods, the remaining five free flowing sections of the Danube are experiencing River bed erosion of the order of several centimetres per year. Besides the effect of interruption of the sediment continuum, River bed degradation is caused by an increase in the sediment transport capacity following an increase in slope, a reduction of River bed width due to canalisation, prohibition of bank erosion by riprap or regressive erosion following base level lowering by flood protection measures and sediment dredging. As a consequence, the groundwater table is lowered, side-arms are disconnected, instream structures are lost and habitat quality deteriorates affecting the ecological status of valuable floodplains. The lack of sediments, together with cutting off meanders, leads also to erosion of the bed of main arms in the Danube Delta and coastal erosion. This paper details the causes and effects of River Engineering measures and hydromorphological changes for the Danube. It highlights the importance of adopting a basin-wide holistic approach to River management and demonstrates that past management in the basin has been characterised by a lack of integration. To-date insufficient attention has been paid to the wide-ranging impacts of River Engineering works throughout the basin: from the basin headwaters to the Danube Delta, on the Black Sea coast. This highlights the importance of new initiatives that seek to advance knowledge exchange and knowledge transfer within the basin to reach the goal of integrated basin management.
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morphodynamic River processes and techniques for assessment of channel evolution in alpine gravel bed Rivers
Geomorphology, 2007Co-Authors: Erik Formann, Helmut Habersack, St SchoberAbstract:Abstract Over the past 10 years many restoration projects have been undertaken in Austria, and River Engineering measures such as spur dykes and longitudinal bank protection, which imposed fixed lateral boundaries on Rivers, have been removed. The EU-Life Project “Auenverbund Obere Drau” has resulted in extensive restoration on the River Drau, aimed to improve the ecological integrity of the River ecosystem, to arrest Riverbed degradation, and to ensure flood protection. An essential part of the restoration design involved the consideration of self-forming River processes, which led to new demands being imposed on River management. This paper illustrates how model complexity is adapted to the solution and evaluation of different aspects of River restoration problems in a specific case. Point-scale monitoring data were up-scaled to the whole investigation area by means of digital elevation models, and a scaling approach to the choice of model complexity was applied. Simple regime analysis methods and 1-D models are applicable to the evaluation of long-term and reach-scale restoration aims, and to the prediction of kilometre-scale processes (e.g. mean River bed aggradation or degradation, flood protection). 2-D models gave good results for the evaluation of hydraulic changes (e.g. transverse flow velocities, shear stresses, discharges at diffluences) for different morphological units at the local scale (100 m–10 m), and imposed an intermediate demand on calibration data and topographic survey. The study shows that complex 3-D numerical models combined with high resolution digital elevation models are necessary for detailed analysis of processes (1 m–0.01 m), but not for the evaluation of the restoration aims on the River Drau. In conclusion, model choice (complexity) will depend on both lower limits (determined by the complexity of processes to be analysed) and upper limits (field data quality and process understanding for numerical models).
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the integrated River Engineering project for the free flowing danube in the austrian alluvial zone national park contradictory goals and mutual solutions
River Systems, 2003Co-Authors: Walter Reckendorfer, Helmut Habersack, Roland Schmalfuss, Christian Baumgartner, Severin Hohensinner, M Jungwirth, F SchiemerAbstract:The Upper Danube River has been almost completely transformed into a chain of impoundments. For the major remaining free-flowing section, the 50 km stretch from Vienna to Bratislava (Alluvial Zone National Park), a large-scale Integrated River Engineering Project has been developed over the last two years. It aims to (1) stop Riverbed degradation, (2) improve navigation, (3) improve fluvial dynamics within the inshore zones, (4) enhance the lateral connectivity between the River and its floodplain and (5) reduce high water levels at flood periods. The decided planning principles focus on an adaptive, step by step implementation and should benefit both the nature values of the area and the navigation. This paper presents the expectations and cornerstones of the project, as well as outlining River Engineering strategies and ecological options. Benefits of the project, potential conflicts between the different stakeholders, and perspectives for the sustainable development of the main channel are discussed.
Reuben A. Heine - One of the best experts on this subject based on the ideXlab platform.
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the use of retro and scenario modeling to assess effects of 100 years River of Engineering and land cover change on middle and lower mississippi River flood stages
Journal of Hydrology, 2009Co-Authors: Jonathan W F Remo, Nicholas Pinter, Reuben A. HeineAbstract:Summary Since the 19th century, the Middle and Lower Mississippi River (MMR and LMR) have been intensively modified for flood protection and commercial navigation. In order to quantify the effects of levee expansion, channel modification, and land-cover change upon flood stages, we have developed 1-D unsteady-flow models of multiple historical reference conditions (“retro-models”) for three large study reaches (225–315 km each): one along the MMR and two reaches along the LMR. For each reference condition, four 1-D unsteady-flow models were developed. These models include a calibrated model of actual conditions and three “scenario” models: (1) a model with levees of the next time step, (2) a model with the channel geometry of the next time step, and (3) a model with floodplain roughness (i.e., land cover) of the next time step. Comparison of the model for actual conditions and the scenario models provide a quantitative assessment of levee expansion, channel modification, and land-cover change on stage. Scenario modeling suggests that the majority (38–70%) of the changes in flood stage on the LMR and MMR study reaches can be attributed to changes in channel geometry and hydraulic roughness. Levees were the next largest contributor to changes in flood stage. For time steps with significant levee expansion, these structures increase stage up to 1.0 m. Observed changes in floodplain land cover were associated with little (or none) of the increase in flood stage. These result show changes in channel geometry and roughness related to River Engineering tools employed for improving navigation and flood protection are the principal dRivers of historic changes in flood stages along these investigated reaches.
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cumulative impacts of River Engineering mississippi and lower missouri Rivers
River Research and Applications, 2009Co-Authors: Nicholas Pinter, Abebe A. Jemberie, Jonathan W F Remo, Reuben A. Heine, Brian S. IckesAbstract:The goal of this study was to construct a large, data-rich model to test hydrological responses to Engineering modifications on over 3200 km of the Mississippi and Lower Missouri Rivers. We compiled model explanatory variables from a geospatial database quantifying construction of all bridges, wing dikes, bendway weirs, levees, artificial meander cutoffs, channel constriction and navigational dams over the past 100-150 years. Response variables were derived from 68 rated and un-rated hydrologic stations in the study area, with responses analysed across a range of discharges from within-channel flows up to moderate floods. Correlation analysis, multiple linear regression and stepwise regression analyses document strong and consistent responses to construction history, both in individual reach-scale models and systemwide. Meander cutoffs are associated with degradation and acceleration of flow that has reduced stages across the full discharge range. Navigational dams on the Upper Mississippi River increased low-flow stages and flood levels to a lesser extent, with little or no post-dam change. One of the strongest signals was the hydrologic response to wing-dike construction, which resulted in large back-water increases in stage upstream of wing dikes and mixed effects downstream, including the overlapping effects of incision and velocity losses. Levees were associated with local flow concentration, overbank storage loss and floodplain conveyance loss depending on reach-scale conditions. The results presented here (1) quantify incremental and cumulative hydrologic responses to a range of Engineering activities and (2) provide an empirical tool for verifying and assessing hydraulic and other models of River-system change. Copyright © 2009 John Wiley & Sons, Ltd.
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Flood trends and River Engineering on the Mississippi River system
Geophysical Research Letters, 2008Co-Authors: Nicholas Pinter, Abebe A. Jemberie, Jonathan W F Remo, Reuben A. Heine, Brian S. IckesAbstract:Along >4000 km of the Mississippi River system, we document that climate, land-use change, and River Engineering have contributed to statistically significant increases in flooding over the past 100–150 years. Trends were tested using a database of >8 million hydrological measurements. A geospatial database of historical Engineering construction was used to quantify the response of flood levels to each unit of Engineering infrastructure. Significant climate- and/or land use-driven increases in flow were detected, but the largest and most pervasive contributors to increased flooding on the Mississippi River system were wing dikes and related navigational structures, followed by progressive levee construction. In the area of the 2008 Upper Mississippi flood, for example, about 2 m of the flood crest is linked to navigational and flood-control Engineering. Systemwide, large increases in flood levels were documented at locations and at times of wing-dike and levee construction.
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hydrodynamic and morphodynamic response to River Engineering documented by fixed discharge analysis lower missouri River usa
Journal of Hydrology, 2005Co-Authors: Nicholas Pinter, Reuben A. HeineAbstract:Abstract This research detects long-term trends in flow conveyance on the Lower Missouri River, and uses equal-discharge analysis of channel-gaging time series to assess the mechanisms driving these trends. Five long-term gaging stations along the Lower Missouri were examined using specific-gage analysis, which is a technique that holds discharge constant in order to observe trends in water-surface elevation (or stage) over time. This analysis reveals that for all flood conditions on the Lower Missouri River, stages have systematically risen for equal discharge volumes over the period of record. Flows that were fully contained within the Missouri channel in the early 20th century now create floods, and extreme high flows today are associated with stages as much as 3.7 m higher than at the start of the record. Equal-discharge analysis also can be used for analyzing time series of other parameters that co-vary strongly with discharge and that change systematically over time. On the Lower Missouri, long-term records of River gaging measurements, including cross-sectional area, flow velocity, and channel width, have been collected for the past ∼70 years. Equal-discharge analysis of these parameters illustrates the mechanisms of channel change driving flood magnification. At three stations, decreased flow velocity has been the dominant mechanism driving stage changes. At two other stations, constriction in channel cross-sectional area has increased flood stages. These changes in channel geometry and flow dynamics correlate with wing-dam construction and other Engineering of the Lower Missouri River, but the changes occur progressively over the duration of record as a gradual and reach-scale re-equilibration of the fluvial system. Magnification of flood stages should be recognized on the Missouri River and incorporated into current estimates of flood hazard and into strategies for River management and flood mitigation in the future.
Bo Wang - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation on the effects of bed slope and tailwater on dam-break flows
'Elsevier BV', 2021Co-Authors: Liu Wenjun, Guo Yakun, Bo Wang, Zhang Jianmin, Chen YunliangAbstract:YesUnderstanding of the characteristics of dam-break flows moving along a sloping wet bed can help to timely issue flood warning and risk mitigation. In this study, laboratory experiments are carried out in a large flume for a wide range of upstream water depth, bed slopes and tailwater depth. The water level is recorded and processed to calculate the mean velocity and wave celerity. Results show that the increase of the bed slope will significantly accelerate the wave-front celerity for the downstream dry bed, while the negative wave celerity will decrease. When water depth ratio α ≥ 0.3 (defined as the ratio of initial downstream water depth over the upstream water depth of dam), there are extra negative waves propagating towards the reservoir area after the flow has developed for a period of time. When α ≥ 0.6, there are the Favre waves propagating downstream. The water level and the mean velocity fluctuate due to the influence of the extra negative waves and the Favre waves. Such fluctuant frequency increases with the increase of the water depth ratio. The empirical formulas are obtained for the celerity of the first extra negative wave and the first downstream wave. The variation of wave-front height is very similar under three bed slopes investigated in this study, while the maximum wave-front height occurs when α = 0.2. The present study broadens the understanding of the effects of the bed slope and the tailwater level on the movement of the dam-break flows. Furthermore, experimental results are also compared with some analytical solutions. The validity of the assumptions made during the development of these analytical solutions and their limitations are discussed by comparing with the experimental measurements.The National Natural Science Foundation of China (Grant No: 51879179), the Open Fund from the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (SKHL1809) and Sichuan Science and Technology Program (No. 2019JDTD0007).The full-text of this article will be released for public view at the end of the publisher embargo on 4th Jul 2021
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SEDIMENT TRANSPORT AND CHANNEL MORPHOLOGY OF A NATURAL AND A LEVEED ALLUVIAL River
LSU Digital Commons, 2019Co-Authors: Bo WangAbstract:Alluvial Rivers are shaped by interactions of flow and sediment transport. Their lower reaches to the world’s oceans are highly dynamic, often presenting Engineering and management challenges. This thesis research aimed to investigate channel dynamics and sediment transport in a natural River and a highly engineered River in South Louisiana, in order to gain much-needed science information for helping develop sustainable practices in River Engineering, sediment management, and coastal restoration and protection. Especially, the thesis research examined (1) Riverbed deformation from bank to bank in the final 500-km reach of the Mississippi River, (2) bed material transport at the Mississippi-Atchafalaya River diversion, and (3) long-term and short-term flood effects on the morphological changes of the Amite-Comite River confluence. The research employed morphological, hydrodynamic, and geospatial modeling and analysis. The research found that from 1992 to 2013 the lowermost Mississippi River channel trapped 337 × 106 m3 sediment, equal to about 70% of Riverine sand input from the upstream channel. The finding rejects the initial hypothesis that the highly engineered Mississippi River acts as a conduit for sediment transport. Sediment deposition mainly occurred in the immediate channel downstream of the Mississippi-Atchafalaya River diversion and the reach between RK 386 and RK 163, reflecting flow reduction and backwater influences. The bed material transport assessment revealed that in the recent decade the Engineering-controlled Mississippi-Atchafalaya River diversion showed a slight disproportional transport of bed material loads. On average 24% of the Mississippi River was diverted into the Atchafalaya, but only 22% of bed material loads moved into the diversion outflow channel (i.e. 47 MT out of 215 MT). The confluence of Amite and Comite River continuously migrated about 55 m downstream between 2002 and 2017. Sediment deposition on the main channel side of the confluence mouth bar is the major dRiver for the confluence migration. Regression analysis shows that the increase rate of the vegetated area of the bar is highly related to the days of moderate floods. Short-term Laser scanning measurements reveal that a single flood with the intensity close to a moderate flood could double the projected surface area of the mouth bar and increased its volume by 68%. Overall, the thesis research shows the complexity of sediment transport in the lower reach of a large alluvial River, in that distinctive bed deformation can occur in different reaches because of flow deduction and backwater effects. Our study is the first try of estimating bed material load at a largely controlled bifurcation based on a simple, well-established bed material transport model. The study also highlights the importance of episodic floods on the evolution and migration of a River confluence
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dynamics of 30 large channel bars in the lower mississippi River in response to River Engineering from 1985 to 2015
Geomorphology, 2018Co-Authors: Bo WangAbstract:Abstract Channel bars are a major depositional feature in alluvial Rivers and their morphodynamics has been investigated intensively in the past several decades. However, relatively less is known about how channel bars in alluvial Rivers respond to River Engineering and regulations. In this study, we assessed 30-yr morphologic changes of 30 large emerged bars located in a 223 km reach of the highly regulated Lower Mississippi River from Vicksburg, Mississippi, to the Mississippi-Atchafalaya River diversion. Landsat imagery and River stage data between 1985 and 2015 were utilized to characterize bar morphologic features and quantify decadal changes. Based on bar surface areas estimated with the satellite images at different River stages, a rating curve was developed for each of the 30 bars to determine their volumes. Results from this study show that the highly regulated River reach favored the growth of mid-channel and attached bars, while more than half of the point bars showed degradation. Currently, the mid-channel and attached bars accounted for 38% and 34% of the total volume of the 30 bars. The average volume of a single mid-channel bar is over two times that of an attached bar and over four times that of a point bar. Overall, in the past three decades, the total volume of the studied 30 bars increased by 110,118,000 m3 (41%). Total dike length in a dike field was found mostly contributing to the bar volume increase. Currently, the emerged volume of the 30 bars was estimated approximately 378,183,000 m3. The total bar volume is equivalent to ~ 530 million metric tons of coarse sand, based on an average measured bulk density of 1.4 t/m3 for the bar sediment. The findings show that these bars are large sediment reservoirs.
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long term geomorphic response to flow regulation in a 10 km reach downstream of the mississippi atchafalaya River diversion
Journal of Hydrology: Regional Studies, 2016Co-Authors: Bo WangAbstract:Abstract A recent study reported considerable sediment trapping by three large channel bars downstream 18–28 km of the Mississippi–Atchafalaya River diversion (commonly known as the Old River Control Structure, ORCS) during the 2011 Mississippi River flood. In this study, we analyzed 3-decadal morphological changes of the 10-km River channel and the three bars to elucidate the long-term effects of River Engineering including diversion, revetment and dike constructions. Satellite images captured between 1985 and 2015 in approximate 5-year intervals were selected to estimate the change of channel morphology and bar surface area. The images were chosen based on River stage heights at the time when they were captured to exclude the temporal water height effect on channel and bar morphology. Using a set of the satellite images captured during the period of 1984–1986 and of 2013–2014, we developed rating curves of emerged bar surface area with the corresponding River stage height for determining the change in bar volume from 1985 to 2013. Two of the three bars have grown substantially in the past 30 years, while one bar has become braided and its surface area has shrunken. As a whole, there were a net gain of 4,107,000 m2 in surface area and a net gain of 30,271,000 m3 in volume, an equivalent of approximately 36 million metric tons of sediment assuming a bulk density of 1.2 t/m3. Sediment trapping on the bars was prevalent during the spring floods, especially during the period of 1990–1995 and of 2007–2011 when large floods occurred. The results suggest that although revetments and dikes have largely changed the morphology of the channel and the bars, they seem to have a limited impact on the overwhelming trend of sediment deposition caused by the River diversion.
