Geomorphology and general systems theory

An appreciation of the value of operating within an appro priate general systematic model has emerged from the recogni tion that the interpretation of a given body of information depends as much upon the character of the model adopted as upon any inherent quality of the data itself. Fluvial geomor phic phenomena are examined within the two systematic models which have been found especially useful in physics and biology closed and open systems, for which simple analogies arei given. Certain qualities of classic closed systems, namely the progres sive increase in entropy, the irreversible character of operation, the importance of the initial system conditions, the absence of intermediate equilibrium states and the historical bias, permit comparisons to be made with the Davisian concept of cyclic erosion. The restrictions which were inherently imposed upon Davis' interpretation of landforms thus become more obvious. It is recognized, however, that no single theoretical model can adequately encompass the whole of a natural complex, and that the open system model is imperfect in that, while embracing the concept of grade, the progressive reduction of relief cannot be conveniently included within it. The open system characteris tic of a tendency toward a steady state by self-regulation is equated with the geomorphic concepts of grade and dynamic equilibrium which were developed by Gilbert and later "dy namic" workers and, despite continued relief reduction, it is suggested that certain features of landscape geometry, as well as certain phases of landscape development, can be viewed prof itably as partially or completely time-independent adjustments. In this latter respect the ratios forming the bases of the laws of morphometry, the hypsometric integral, drainage density, and valley-side slopes can be so considered. The relative values of the closed and open systematic frameworks of reference are recognized to depend upon the rapidity with which landscape features can become adjusted to changing energy flow, and a contrast is made between Schumm's (1956) essentially open system treatment of weak clay badlands and the historical ap proach which seems most profitable in treating the apparently ancient landscapes of the dry tropics. 1 Goethe, Fragment liber die Natur (1781-82) : Translated from Goethe's samtllche Werke, Jubilaumsausgabe, Stuttgart and Berlin, v. 39, p. 3-4, undated. Finally, seven advantages are suggested as accruing from attempts to treat landforms within an open system framework: