Toward a theory for step pools in stream channels

Over the past 10 to 15 years there has been a surge in interest in step-pool streams in fluvial geomorphological research. This reflects recognition of the geomorphic significance of step pools in high-gradient channels, and a growing interest in rivers in mountainous regions in general. This paper synthesizes the recent literature on step pools, with particular reference to theory construction and progress made over the past decade and a half. Four groups of contributions are identified. The first focuses on understanding morphological relations in order to seek causal mechanisms. The second emphasizes processes that result from the step-pool configuration. The third is a group of integrative studies that seek broader explanations for step-pool sequences. The fourth and growing body of literature applies what has been learned about step pools toward managing and restoring steep channels. We conclude by highlighting some future possible research directions toward gaining a complete explanation for step pools in stream channels.