A SIMULATION-MODEL FOR MEANDERING RIVERS

A computer model for the dynamics of meandering rivers has been used t o study the interplay between the migrating river and the changing sed imentary environment created by the meandering river itself. The model is based on. the theory of Ikeda et al. [1981] and is closely related to that proposed by Howard [1983]. Coarser sands, which are often ass ociated with high erodibility, are deposited in the point bars formed when the river migrates away from its former bank. Fine-grained materi al eventually fills the oxbow lakes created by cutoff processes and fo rms erosion-resistant plugs. In the simulations, geometric forms of in dividual meanders observed in different natural sedimentary environmen ts have been reproduced by changing the erodibility of the correspondi ng sedimentary materials, such as point bar deposits, flood plain depo sits, and oxbow lake deposits. The simulations indicate that the typic al meander wavelength is determined mainly by hydraulic factors such a s the flow in the channel and the inclination of the underlying flood plain and is independent of the difference in the erodibilities of sed imentary deposits. The computational approach permits exploration of l ong-term changes in the floodplain geology, mediated by the meandering river. As an initial demonstration, the formation of meander belts is investigated using the model. The results suggest that a meander belt will be formed by a river's own cutooff loops only if the characteris tic time of deposition and solidification of an oxbow lake is longer t han the typical time that it takes the river to migrate downstream ove r the distance of a meander-loop wavelength.