Rill and Gully Development Processes

Rills and gullies are common and generally companion geomorphological features on hillslopes, but they are different both morphologically and mechanically. By introducing the concepts and classifications of both rills and gullies, this chapter describes the physical processes causing the development of rills, followed by an overview of research methods for characterizing the mechanics of rill erosion and modeling rill development. Compared with rill erosion, gully initiation and erosion are more complex as they are controlled by both surface and subsurface processes. As a result, much more diverse approaches have been developed both to quantify gully headwall retreat and sidewall erosion and to characterize gully development.