New Closure Schemes in 3D SedFlux for the Simulation of Deltas

Syvitski, James P. M.¹, Eric W. H. Hutton¹ (1) INSTAAR CU-Boulder, Boulder, CO

Quantitative forward models used to simulate basin evolution are accounting systems able to track an evolving accommodation space (e.g. base level, sea level, tectonics) during which sediment is delivered, dispersed and accumulated within a basin. However there remain sedimentary environments where the conservation equations cannot be adequately closed due to a lack of understanding of the underlying processes. Relationships developed from global databases provide an opportunity to test new approaches at closure, but also provide formulations to employ as closure schemes when all else fails. For example, the basin fill model Sedflux is used to predict a delta's area through a series of model runs with varying discharge, sediment supply, marine power and accommodation space (shelf depth). Model predictions are compared to predictive statistical relationships obtained from observations of 60 Holocene deltas as a test of Sedflux's delta module closure scheme. Examples of using global relationships for closure within the delta module of Sedflux include formulae to predict the number of distributary channels and the width of these various distributary channels. The channel number closure is based on bankfull discharge and marine power. The channel width closure use a lognormal distribution, with the total width a function of bankfull discharge, tidal and wave energy. These various closure experiments also employ the new BQART model to initialize the sediment delivery into Sedflux, as conditioned by geomorphic and tectonic influences (basin area and relief), geography (temperature, discharge), geology (lithology, ice cover), and basin perturbations (reservoir trapping, anthropogenic-caused erosion).