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.

This chapter reviews in detail the dynamics of anastomosing and anabranching river systems. The difference between anastomosing and anabranching rivers as well as the difference between anastomosing/anabranching and braided rivers is outlined in detail. Anastomosing rivers are examined as a distinctive form of low-energy fluvial systems and of the world’s largest rivers. Anabranching is introduced as a generic type of multichannel river form of which anastomosing is a distinct subcategory. Mechanisms of avulsion, the key process associated with dynamic change of anabranching rivers, are reviewed. The dynamics of wandering gravel-bed rivers, a distinctive type of anabranching river, are explored along with examples of other types of anabranching systems, including those in dryland environments.