This chapter examines the dynamics of meandering rivers, including the initiation of meandering in straight channels; the development of bar units; and the relation of these units to pools, riffles, and point bars. It reviews theories of pool-riffle development and maintenance; flow through meander bends, including the influence of channel curvature and the point bar on flow structure; and the relation of the spatial pattern of shear stress in curved channels to patterns of erosion and deposition, to the development of bar unit topography, and to patterns of bank erosion. Mechanisms of bank erosion are introduced, emphasizing that bank erosion occurs in different types of rivers. Modes of planform deformation on meandering rivers are explored, as well as the factors that influence planform migration dynamics in meandering rivers. The discussion includes a basic introduction to numerical models of meandering rivers and attempts to integrate models of flow and sediment transport in curved channels with models capable of simulating bank erosion and lateral migration of meandering rivers. The chapter also briefly discusses meandering of mixed bedrock-alluvial rivers.

This chapter reviews general understanding of the factors that control planform characteristics of rivers. It first introduces the major planform types – straight, meandering, braided, and anabranching – and discusses the distinguishing characteristics of each type. Environmental domains of each planform type, particularly in relation to stream power and sediment characteristics, are then discussed. The chapter examines transitions between planform states and the notion of whether channel planform changes over a continuum or is governed by thresholds that separate distinct domains of planform behavior. It also discusses recent work suggesting that the largest rivers in the world exhibit planform characteristics that differ from those for small rivers. The chapter serves as the foundation for detailed discussions of the dynamics of different planform types in subsequent chapters.