A test of equilibrium theory and a demonstration of its practical application for predicting the morphodynamics of the Yangtze River

摘要

Taking thewidth/depth ratio of a river channel as an independent variable, a variational analysis of basic flowrelationships shows that alluvial-channel flow adjusts channel geometry to achieve stationary equilibrium when the condition of maximum flow efficiency (MFE) is satisfied. As a test of the veracity of MFE and to examine if this theory of self-adjusting channel morphodynamics can be practically applied to large river systems, this study examines the degree of correspondence between theoretically determined equilibrium channel geometries and actual measurements along the middle and lower Yangtze River. Using four different forms of the Meyer-Peter and Müller bedload relation and relations of flowcontinuity and resistancewe showthat theMeyer-Peter andMüller bedload relation modified on the basis of MFE theory predicts channel dimensionsmost accuratelywhen applied to themiddle and lower Yangtze River. This provides convincing evidence supporting MFE equilibrium theory.