River configurations in plan view are highly variable. Under specific environmental and hydraulic conditions, the type of planform geometry of a river is controlled by the sediment transport and its capacity of the river. Alluvial river configurations are in general categorized as straight, meandering, and braided rivers. While long, straight rivers seldom occur in nature; meandering and braided rivers are common. This chapter focuses on the characteristics of meandering and braided rivers. Mathematical models of meandering rivers are presented. © 2014, Springer-Verlag Berlin Heidelberg.