The Spatial Arrangement of River Systems

A diverse array of physical structures may exist between and within riverine landscapes. Broad-scale patterns in the spatial arrangement of riverine landscapes are observed despite variations in the influence of independent catchment and channel variables. Rivers are continually evolving in response to longer-term natural disturbances, shorter-term pulsed or ramped human interventions, and high magnitude, low-frequency episodic events. Responses may be cyclic, nonlinear, and/or lagged, and the effects of single or multiple disturbance may overlap and interact, thereby increasing the probability of alternative states in river systems. This view of riverine landscapes moves away from notions of equilibrium and cyclic behavior as a means to explain nonlinear relationships and stochasticity. Recent views of river systems emphasize the importance of scale and their hierarchical organization, acknowledging both top-down constraints and the emergent features of bottom up influences. Contrasting views of the clinal and patch approach to the spatial arrangement and behavior of riverine landscapes reflect the differences between Darwinian and Newtonian approaches to science in some way. The former embraces the principles of complexity, contingency, and interdependence, while the latter strives for simplification, ideal systems, and predictive understanding. This chapter discusses concepts and theoretical approaches to the spatial arrangement of riverine landscapes. Following this, a review of the river characterization is presented. In particular, the results of a meta-analysis of the more commonly used river characterization schemes are presented. A characterization scheme for riverine landscapes then presented, and its application demonstrated with two case studies: the Murray–Darling Basin, Australia, and some of the rivers in the Kingdom of Lesotho, Africa.