Fluxes of mass and energy in hydrological and geomorphological processes, and in environmental systems in general, preferentially select and reinforce the most efficient pathways. In doing so, they also tend to selectively preserve the most stable and resistant materials and structures, and remove the weaker and unstable ones. This suggests that Earth surface systems should generally evolve toward more efficient flux paths and networks, and a prevalence of stable and resistant forms. The purpose of this essay is to explore why the attractor condition of maximum efficiency and stability is not fully attained.
Numerous theories, hypotheses, and conceptual frameworks exist in geosciences that predict or seek to explain the development of flow paths in Earth surface systems (ESS). These include so-called “extremal” principles and the least action principle in hydrology and fluvial geomorphology, principles of preferential flow in hydrology, constructal theory, and various optimality principles in geophysics and ecology.