Soil erosion has been divided traditionally into sheet, rill, and gully erosion. In rills and gullies, overland flow is concentrated, which markedly increases the erosivity of the flow, and can cause then significant incisions into the landscape. Usually rills occur on sloping surfaces, whereas gullies occur within swales or hollows. Concentrated flow erosion represents an important -if not the dominant- sediment source within watersheds, producing sizeable economic losses. It is also an important process for transient landscape evolution. These channels are effective links for transferring runoff, sediment and other materials thereby increasing landscape connectivity. The complex physical mechanisms involved in concentrated flow erosion still require more research for a better understanding, with the ultimate aim of developing prediction technology and effective management strategies.

Channel erosion plays a key role in the development of badlands. Many years have passed since different definitions stated the term “badlands” referring to “densely dissected areas that are severely degraded and within which soil has been removed or has lost most of its fertility” (Fairbridge, 1968), or to “intensely dissected natural landscapes within which vegetation is sparse or absent and that are unsuitable for agriculture” (Bryan and Yair, 1992), as well as to “areas of unconsolidated sediments or poorly consolidated bedrock that contain little or no vegetation” (Gallart et al., 2002). Many techniques and experimental procedures have been applied for years in these environments in order to investigate their origin and evolution, the geomorphic processes that occur, their hydrological and erosive response as well as soil erosion processes after different types of rainfall events, the difficulties of vegetation to colonize them, among others questions. Despite the term ‘badlands’ evokes the difficult exploitability of such territories, the impact of human activity on these landscapes, as well as their potential as geoheritage resources put them under the spotlight for future environmental investigations.

The session pretends to address mainly the following topics: rills and gullies monitoring, measurement techniques, controlling factors, processes, modelling, restoration and control, role in hydrological and sediment connectivity; recent findings and investigations on badland environments worldwide, applying all sort of techniques and procedures in field, laboratory and modelling, in order to discuss the state-of-art and shed light on the main milestones and challenges we should face in future investigations to widen the knowledge about them.


References

Bryan RB and Yair A (1982) Badland Geomorphology and Piping. Norwich: Geo Books, 408 pp.
Fairbridge RW (ed.) (1968) Encyclopaedia of Geomorphology. New York: Reinhold Book Corp., 1295 pp.
Gallart F, Solé A, Puigdefábregas J and Lázaro R (2002). Badland systems in the Mediterranean. In Bull JL and Kirkby MJ (eds) Dryland Rivers: Hydrology and Geomorphology of Semi-arid Channels. Chichester: Wiley, 299–326.