Two small drainage networks were developed from an earth-fill model subjected to artificial rain. Evolution of the basins in time for both runs indicates an exponential growth of basin size, total stream length, and number of streams. When the basins attained a fixed size controlled by the dimensions of the container, these parameters reached a steady state that prevailed for the remainder of the experiment. Drainage density also increased exponentially, while the relative drainage density, measured from the area directly eroded, maintained uniform values throughout “youth” and “maturity.” The profile of the longest stream was exponential and retained an equilibrium form for the duration of the experiment, in spite of a marked decrease in stream gradient with time. The hypsometric integral decreased rapidly during the early stages of development, possibly changing to a linear function of slower rate after the basin had become areally fixed.
Although many natural conditions could not be simulated in the model, the quasi-equilibrium state reached in the parameters that were measured and the similarity between the empirical data and known geomorphic relations suggest that experimental models of drainage networks may provide a useful approach to the study of basin evolution.