MODELING OF MEANDERING AND BRANDING IN RIVERS.

THE RESULTS OF STABILITY ANALYSES OF MEANDER- AND BRAID-LIKE PERTURBATIONS IN STRAIGHT RIVERS ARE USED TO CONSTRUCT A DIAGRAM DIVIDING RIVERS INTO STRAIGHT, MEANDERING, AND BRAIDED REGIMES.THE SAME ANALYSIS PROVIDES ORDER-OF-MAGNITUDE ESTIMATES OF MEANDER AND BRAID LONGITUDINAL WAVELENGTH AND BRAID NUMBER.THE RELATIONS INDICATE THAT IF THE GEOMETRIC AND FROUDE CRITERIA ARE APPLIED TO RIVER MODELS, AND IF SEDIMENT TRANSPORT EXISTS IN BOTH THE MODEL AND THE PROTOTYPE, THE OCCURRENCE OF MEANDERING AND BRAIDING AND INCIPIENT MEANDER AND BRAID WAVELENGTHS ARE MODELLED TO THE CORRECT ORDER OF MAGNITUDE.SEDIMENT TRANSPORT ITSELF NEED NOT BE MODELLED AS LONG AS IT EXISTS.THE ANALYSIS JUSTIFIES THE USE OF LIGHT BED MATERIAL SUCH AS COAL OR PLASTIC RATHER THAN SAND IN RIVER MODELS AS A MEANS OF ENSURING THE EXISTENCE OF SEDIMENT TRANSPORT, IN THAT THE INITIAL TENDENCIES TOWARD MEANDERING OR BRAIDING ARE NOT GREATLY ALTERED.THE MODELING METHOD IS USEFUL FOR TESTING THE EROSIVE TENDENCIES OF STREAMS THAT HAVE BEEN CHANNELIZED IN A STRAIGHT ALIGNMENT; SUCH STREAMS OFTEN SHOW A TENDENCY TO RETURN TO THE ORIGINAL MEANDERING OR BRAIDING STATE.(A).