[PDF] Comparison Of The Morphological Development Of Unconfined Skewed Alluvial Laboratory Meandering Streams In Response To Low And High Flow Rate Conditions eBook

Author : David Nguyen
Publisher :
Page : pages
File Size : 50,84 MB
Release : 2020
Category :
ISBN :

GET BOOK

Past research on meandering rivers with skewed planform geometries has shown that skewness orientation impacts patterns of hydraulic conditions and morphological changes. The purpose of this work was to expand on that knowledge by testing different degrees of skewness and discharge conditions. A laboratory flume was used to test two unconfined skewed alluvial meandering river channels with opposite skewness orientations. Values of skewness were chosen to be different from past research for later comparisons. Experiments began at a low flow condition until equilibrium was achieved, at which time the discharge was increased to a higher value until equilibrium was reached again. Data was collected for flow rate, flow depth, and bedload transport, while elevation data was obtained using photogrammetric techniques. Results showed evidence for increased stability in the upstream skewed orientation with larger flow resistance, while the downstream skewed orientation adjusted towards a more symmetric (ex. non-skewed) channel over time.

Author : Ryan Good
Publisher :
Page : pages
File Size : 43,41 MB
Release : 2018
Category :
ISBN :

GET BOOK

Rivers typically follow a meandering pattern where, over time, the river adjusts its morphology to minimize the channel slope. The purpose of the research is to better understand the morphological patterns associated with skewed meander bends in an unconfined alluvial channel. Physical modelling of meandering streams with three different skewness coefficients was conducted in a laboratory flume. Sediment was collected at the outlet to quantify transport rates, the bed was monitored using Structure-from-Motion photogrammetry, and flow rates were monitored with an ultrasonic flowmeter. The flow was stopped periodically to quantify the morphological development of the stream with time. The results provide insight into the time to development of morphological changes as well as the physical processes that dictate the scale and pattern of the changes observed. The results included channel geometry adjustments to reduce the bed shear stress and energy grade line slope, as well as observations on morphological patterns.

Author : Christopher Sullivan
Publisher :
Page : pages
File Size : 41,40 MB
Release : 2018
Category :
ISBN :

GET BOOK

Understanding fluvial processes in rivers and streams and their interactions with each other enable for more effective channel designs, improved erosion control measures, and more resilient systems. The use of an unconfined river basin flume (5.6 m in length x 1.9 m in width) allowed for analysis of the interactions between sediment transport rates, bed development, and planform morphological adjustments in an unconfined alluvial meandering stream. Three tests were completed including one quasi-unsteady hydrograph experiment. It was found that the largest bank morphological adjustments coincided with considerable bed development and sediment transport rates; agreeing with previous field and laboratory observations. Morphological evolution appears to follow an exponential growth profile, with the majority of bed development and bank erosion occurring during the early stages of a run or during the rising limb of the hydrograph. Results from this research proposed relationships between discharge, sediment transport and channel morphology in alluvial meandering streams.

Author : Kirstie A. Fryirs
Publisher : John Wiley & Sons
Page : 650 pages
File Size : 31,38 MB
Release : 2012-09-26
Category : Science
ISBN : 1118305442

GET BOOK

Filling a niche in the geomorphology teaching market, this introductory book is built around a 12 week course in fluvial geomorphology. ‘Reading the landscape’ entails making sense of what a riverscape looks like, how it works, how it has evolved over time, and how alterations to one part of a catchment may have secondary consequences elsewhere, over different timeframes. These place-based field analyses are framed within their topographic, climatic and environmental context. Issues and principles presented in the first part of this book provide foundational understandings that underpin the approach to reading the landscape that is presented in the second half of the book. In reading the landscape, detective-style investigations and interpretations are tied to theoretical and conceptual principles to generate catchment-specific analyses of river character, behaviour and evolution, including responses to human disturbance. This book has been constructed as an introductory text on river landscapes, providing a bridge and/or companion to quantitatively-framed or modelled approaches to landscape analysis that are addressed elsewhere. Key principles outlined in the book emphasise the importance of complexity, contingency and emergence in interpreting the character, behaviour and evolution of any given system. The target audience is second and third year undergraduate students in geomorphology, hydrology, earth science and environmental science, as well as river practitioners who use geomorphic understandings to guide scientific and/or management applications. The primary focus of Kirstie and Gary’s research and teaching entails the use of geomorphic principles as a tool with which to develop coherent scientific understandings of river systems, and the application of these understandings in management practice. Kirstie and Gary are co-developers of the River Styles® Framework and Short Course that is widely used in river management, decision-making and training. Additional resources for this book can be found at: www.wiley.com/go/fryirs/riversystems.

Author : Adrian M. Harvey
Publisher : Geological Society of London
Page : 258 pages
File Size : 31,87 MB
Release : 2005
Category : Science
ISBN : 9781862391895

GET BOOK

Alluvial fans are important sedimentary environments. They trap sediment delivered from mountain source areas, and exert an important control on the delivery of sediment to downstream environments, to axial drainages and to sedimentary basins. They preserve a sensitive record of environmental change within the mountain source areas. Alluvial fan geomorphology and sedimentology reflect not only drainage basin size and geology, but change in response to tectonic, climatic and base-level controls. One of the challenges facing alluvial fan research is to resolve how these gross controls are reflected in alluvial fan dynamics and to apply the results of studies of modern fan processes and Quaternary fans to the understanding of sedimentary sequences in the rock record. This volume includes papers based on up-to-date research, and focuses on three themes: alluvial fan processes, dynamics of Quaternary alluvial fans and fan sedimentary sequences. Linking the papers is an emphasis on the controls of fan geomorphology, sedimentology and dynamics. This provides a basis for integration between geomorphological and sedimentological approaches, and an understanding how fluvial systems respond to tectonic, climatic and base-level changes.

Author : Bruce L. Rhoads
Publisher : Cambridge University Press
Page : 544 pages
File Size : 44,50 MB
Release : 2020-04-29
Category : Science
ISBN : 1108173780

GET BOOK

Rivers are important agents of change that shape the Earth's surface and evolve through time in response to fluctuations in climate and other environmental conditions. They are fundamental in landscape development, and essential for water supply, irrigation, and transportation. This book provides a comprehensive overview of the geomorphological processes that shape rivers and that produce change in the form of rivers. It explores how the dynamics of rivers are being affected by anthropogenic change, including climate change, dam construction, and modification of rivers for flood control and land drainage. It discusses how concern about environmental degradation of rivers has led to the emergence of management strategies to restore and naturalize these systems, and how river management techniques work best when coordinated with the natural dynamics of rivers. This textbook provides an excellent resource for students, researchers, and professionals in fluvial geomorphology, hydrology, river science, and environmental policy.

Author : Etta Haley Gunsolus
Publisher :
Page : 316 pages
File Size : 32,19 MB
Release : 2015
Category :
ISBN :

GET BOOK

Changes in riverine discharge, such as those due to reservoir flushing, seasonal variation or extreme precipitation, can alter sediment transport rates and morphology of the stream bed. Experimental laboratory research investigated the effect of unsteady flow event hydrographs on stream bed morphological response. Laboratory experiments were conducted in a 5.0 mlong sediment transport flume with a bed comprised of a medium sand. Experimental hydrographs were composed of antecedent (base-flow), unsteady event (flood) and post-flood (return to base-flow) stages. Three distinct series of experimental laboratory runs were conducted to systematically investigate the effect of three characteristics of unsteady flow event hydrographs. Series A investigated the effect of the magnitude of the unsteady flow event hydrograph; Series B investigated the effect of the duration of the event; and Series C investigated the effect of the hydrograph shape (i.e., time-to-peak flow). Bed morphological adjustments, sediment transport rates and the composition of the sediment in transport were measured throughout all stages of the experimental runs. Measured values were compared to predicted values calculated using traditional sediment transport and bed form geometry equations assuming steady flow conditions. In general, predicted values greatly underestimated both measured values of sediment transport and bed form geometry. Results show that systematic changes in the magnitude, duration and time-to-peak flow of the unsteady hydrograph cause varying types of hysteresis (clockwise or counter-clockwise) of the sediment transport rates which has a considerable effect on the subsequent bed morphological adjustments. Shorter duration and symmetrical hydrographs exhibit counter-clockwise hysteresis while longer duration and asymmetrical hydrographs exhibit clockwise hysteresis. Results from this thesis have made considerable contributions towards evaluating the effects of unsteady flow event hydrograph characteristics to improve numerical modelling capabilities and accuracies, as well as river and dam management, engineering and restoration.