This article reviews previous investigations into gully and badland research and discusses processes and definitions in the context of existing research in southeast Spain. The theory of badland development is summarized and definitions are proposed which draw on previous work and continuing studies. The processes influencing gully and channel head morphology are then discussed including overland flow, hillslope processes, pipe initiation and enlargement, mass failures and the magnitude and frequency distribution of storm events. Finally, modelling of badland landscapes is discussed. The article highlights that much detailed research has been carried out on badlands, but long-term rates of gully development are not well understood. There are also gaps in our understanding of pipe network formation and collapse. In the short term theoretical modelling may provide the way forward and a direction for more holistic investigations.