Developments in Dynamic Modelling of Meandering Fluvial Systems

Numerical modelling of meandering rivers has been of rising interest for the oil companies facing heterogeneous reservoirs associated with such fluvial systems. Thirty years ago, an original migration model for meandering rivers was proposed by Ikeda, Parker and Sawai. Arising from the Saint-Venant equations for shallow water, it was based upon a curvature-induced transverse perturbation in the velocity field. Several simplifying assumptions were made, especially channel width and streamwise slope considered as constant. Following this pioneering work, several authors have extended the model to include small variations of width or slope. However no simple model was proposed until now to simulate a meandering flow over an irregular topography while loosening the unchanging width constraint.

The starting point of the present development is a process-based model able to simulate the long-term evolution of the floodplain associated to a meandering river. The part related to the bed evolution greatly inherits from mentioned historical models. In order to enlarge the domain of application of the model and to improve its physical basis, two major developments were made. First the flow module was adapted by using Saint-Venant equations in curvilinear coordinates that inherently contain the channel curvature and its width variations. Secondly a multi-class sediment transport model was included, based on a transverse splitting of the river section to determine eroded or deposited sediment quantity in parts of each section. Therefore, a method is used, that determines which variations of the sections parameters (migration, width, mean bed elevation and transverse inclination) match the computed transport.

As a result, the final floodplain model gives simulations that have a better physical basis in hydrology and sedimentology, including grain-size variations of the deposits. Therefore, the simulations can now include allogenic parameters, sedimentary supply and base-level variations, that constrains river behavior in a realistic geological context.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California