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.

Libro de abstracts del congreso celebrado en Santander en junio de 2013.

A stream flowing in alluvium deforms its bed surface, forming ripples, dunes, bars, etc., and, in many instances, it deforms its channel entirely, thereby creating meandering or braiding patterns. It could be said that, in general, an alluvial stream and its deformable boundary undergo a variety of fluvial processes leading to the emergence of a multitude of alluvial forms. This book concerns the physics and analytical treatment of various fluvial processes and the associated alluvial bed and plan forms listed above. Following an introductory chapter on the basics of turbulent flow and sediment transport, the book covers the origin, geometric characteristics and effects of bed forms, from small- to meso-scale (ripples, dunes, alternate and multiple bars); the initiation, geometry and mechanics of meandering streams; the computation of flow, bed deformation and the planimetric evolution of meandering streams; and braiding and delta formation. The book also covers the regime concept, the time-development of a stream towards its regime state, and the formulation of stable, or equilibrium, morphology. The book distinguishes itself by its comprehensive analysis and discussion of key processes involved in large-scale river morphodynamics. The book was written primarily for researchers and graduate students of hydraulic engineering, water resources and related branches of earth sciences, but it will also prove useful for river engineers and managers.

Sediment transport dynamics, often heavily modified by river training, are not yet sufficiently considered as a significant factor in riparian environmental quality and river restoration strategies. Approaches for restoring a river's sediment in quantity and in grain size distribution, so that it is compatible with both ecological and human needs, are still under development. Furthermore, existing approaches such as direct sediment injection are often expensive and require human intervention. This thesis explores induced bank erosion, a more environmentally sustainable alternative. This approach involves increasing the potential for erosion at certain sites along the bank of a trained river, and allowing them to be eroded during high flow periods. Two modelling approaches, physical scaled models and numerical simulation, were used to study a site located on the Old Rhine downstream of Basle (Switzerland) where existing bank protection groynes will be modified to induce bank erosion. Firstly, different modification options were tested over a range of flow rates with a Froude-scaled undistorted movable-bed physical model. The physical model used a mixture of four grain sizes to reproduce the bank grain size distribution found at the site, and was scaled according to a specific method which accurately represents initiation of motion for each grain size. An effective bank erosion strategy was found that releases sediment without compromising the safety of an adjacent navigation channel through excessive bank retreat. Subsequently, the capability of the Telemac2D two-dimensional depth-averaged numerical modelling system to model bank erosion and failure processes was assessed, and the existing bank failure algorithm was modified in order to improve results. Algorithm developments were tested with two laboratory test cases. Then, the physical model tests were simulated at their same scale. Simulations reproduced the processes present in the physical model tests, and volumes of eroded and deposited sediment were of the same order of magnitude.

Bank erosion is a dominant river morphodynamic process resulting in encroaching valuable farming land and channel migration. Prediction of bank erosion and channel migration requires understanding of the morphodynamics of the entire river system. Numerical modeling is an ideal method for this task. However, models with full capabilities and applications on complex real-world problems are rare. In this study the finite element-based computational model, CCHE2D, and its flow, sediment transport, and bank erosion modules are introduced. The model is capable of simulating unsteady flows with nonuniform sediment transport and cohesive/non-cohesive material bank erosion. The effects of helical secondary current on sediment transport induced by flow curvatures are reflected in both bed load and suspended sediment formulations. This model is validated using multiple sets of experimental data and applied to bank erosion problems of the Chuoshui River, a real-world mountain river in Taiwan. Characterized by typhoon floods, steep channel slopes, and high sediment load and mobility, this river often exhibits a braided pattern consisting of multiple curved channels. Channel bed change and bank erosion caused by 10 years of typhoon floods in a selected reach have been simulated, and the computed bank erosion results agreed with the field observation.

Rivers form one of the lifelines in our society by providing essential services such as availability of fresh water, navigation, energy, ecosystem services, and flood conveyance. Because of this essential role, mankind has interfered continuously in order to benefit most and at the same time avoid adverse consequences such as flood risk and droughts. This has resulted in often highly engineered rivers with a narrow set of functions. In the last decades rivers are increasingly considered in a more holistic manner as a system with a multitude of interdependent processes. River research and engineering has therefore added to the river fundamentals also themes like ecohydraulics, consequences of climate change, and urbanisation. River Flow 2020 contains the contributions presented at the 10th conference on Fluvial Hydraulics, River Flow 2020, organised under the auspices of the Committee on Fluvial Hydraulics of the International Association for Hydro-Environment Engineering and Research (IAHR). What should have been a lively physical gathering of researchers, students and practitioners, was converted into an online event as the COVID-19 pandemic hindered international travelling and large gatherings of people. Nevertheless, the fluvial hydraulics community showed their interest and to be very much alive with a high number of participations for such event. Since its first edition in 2002, in Louvain-la-Neuve, this series of conferences has found a large and loyal audience in the river research and engineering community while being also attractive to the new researchers and young professionals. This is highlighted by the large number of contributions applying for the Coleman award for young researchers, and also by the number of applications and attendants to the Master Classes which are aimed at young researchers and students. River Flow 2020 aims to provide an updated overview of the ongoing research in this wide range of topics, and contains five major themes which are focus of research in the fluvial environment: river fundamentals, the digital river, the healthy river, extreme events and rivers under pressure. Other highlights of River Flow 2020 include the substantial number of interdisciplinary subthemes and sessions of special interest. The contributions will therefore be of interest to academics in hydraulics, hydrology and environmental engineering as well as practitioners that would like to be updated about the newest findings and hot themes in river research and engineering.