アイテム詳細

要旨

The organization of drainage basins shows some
reproducible phenomena, as exemplified by self-similar fractal
river network structures and typical scaling laws, and
these have been related to energetic optimization principles,
such as minimization of stream power, minimum energy expenditure
or maximum “access”. Here we describe the organization
and dynamics of drainage systems using thermodynamics,
focusing on the generation, dissipation and transfer
of free energy associated with river flow and sediment
transport. We argue that the organization of drainage basins
reflects the fundamental tendency of natural systems to deplete
driving gradients as fast as possible through the maximization
of free energy generation, thereby accelerating the
dynamics of the system. This effectively results in the maximization
of sediment export to deplete topographic gradients
as fast as possible and potentially involves large-scale feedbacks
to continental uplift. We illustrate this thermodynamic
description with a set of three highly simplified models related
to water and sediment flow and describe the mechanisms
and feedbacks involved in the evolution and dynamics
of the associated structures. We close by discussing how
this thermodynamic perspective is consistent with previous
approaches and the implications that such a thermodynamic
description has for the understanding and prediction of subgrid scale organization of drainage systems and preferential flow structures in general.