Evolution of an anthropogenic desert gully system.

Studies of an unusual quasi-stationary desert gully permit the description of a system attractor which may be inherent, if rarely physically expressed, in many gully systems. Measurements made in a desert gully system (controlled by the seepage of irrigation waters towards a stable base level) suggested a character for the attractor's equilibrium manifold. This was modelled mathematically as an hysteresis or limit cycle in phase space. Overall, the phenomenon is seen to belong to a kind of hierarchical process associated with the Scheidegger 'principle of instability/saturation effect". It reflects a dynamic balance between two hierarchical levels inside a single system. The system includes a singularity which is an example of an hierarchical jump caused by the reintegration of a self-assertive holon. (A)