This monograph discusses the mechanics of Meandering Rivers with the help of the mathematical and modeling tools built up in the previous monograph of the same Authors (monograph 1 of the present series). After introducing the reader to the ubiquitous character of meandering streams, we discuss the hydrodynamics of curved channels with fixed beds and banks. Next, we extend the analysis to account for the mobile character of the bed and show that it gives rise to the alternate sequence of riffles and pools that characterize river meanders. Allowing for the erodible character of the river banks then allows to build up a rational theory of meander formation able to explain most of the features observed in nature: meander growth, migration, skewing, multiple loops, cutoffs and meander belts.

This thesis examines the morphological changes of non-tidal meandering rivers at the spatial scale of several meanders. With this purpose, a physics-based mathematical model, MIANDRAS, has been developed for the simulation of the medium-term to long-term evolution of meandering rivers. Application to several real rivers shows that MIANDRAS can properly simulate both equilibrium river bed topography and planimetric changes. Three models of different complexity can be obtained by applying different degrees of simplification to the equations. These models, along with experimental tests and field data, constitute the tools for several analyses. At conditions of initiation of meandering, it is found that river bends can migrate upstream and downstream. This depends on meander wave length and width-to-depth ratio, irrespective of whether the parameters are in the subresonant or the superresonant range.

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.

The sinuous form and peculiar evolution of meandering rivers has long captured the imagination of people. Today, meandering rivers exist in some of the most densely populated areas in the World, where they provide environmental and economic wealth and opportunities, as well as posing hazards. Through geological time, the ancestors of these modern meanders built deposits that are now host to mineral resources, groundwater, and hydrocarbons. This Special Publication illustrates the breadth of current research on meandering rivers and their deposits. The collection of research papers demonstrates the state of science on fluvial process–product relationships. The articles cover fundamental and applied studies of both modern and ancient rivers, are based on state-of-the-art technology, include complementary philosophical approaches, and span a wide range of spatial and temporal scales. This book includes some of the most recent advances in the study of the morphodynamics and sedimentology of meandering rivers, and is an important resource for those who want to investigate fluvial systems and their deposits.

This thesis has been devoted to three different problems related to the morphodynamics of rivers. The first of them concerns sediment transport, for which a two-phase flow model has been proposed, valid in both viscous and turbulent regimes. As a main result, this model describes the transition from bed load to suspended load when the Shields number is increased. The second subject was the formation of bars. We revisited the linear stability analysis of these bedforms in order to emphasize the role played by the saturation length. We have shown that this saturation length controls the transition from ripples to bars. The third and most developed aspect of this PhD work was dedicated to the formation of meanders. By means of 3D RANS equations, we have performed a detailed description of hydrodynamics in a channel with both modulated bed and undulating banks. Coupled to sediment transport, the linear stability analysis of the problem gives predictions for the growth rate, the migration velocity and the shape of the bed for given meandering banks of wavenumber k. These predictions are in quantitative agreement with experimental data we obtained in a small flume: the entire dispersion relation is fitted with reasonable parameters of the modeling, but also the bed modulation is correctly reproduced. On the qualitative sicle, we have identified the mechanism responsible for this instability. This mechanism is different to thàt proposed by Einstein and it is also different to the resonance proposed by Blondeaux & Seminara. Finally, we have shown that depth-averaged (Saint-Venant) equations are not able to reproduce the instability.