Simulation of birdfoot delta formation with application to the Mississippi Delta

Recently, Seybold et al. (2007) proposed a reduced complexity model which simulates the process of delta formation on geological time scales. It includes subaerial and subaqueous growth in a three-dimensional framework. In this paper we apply this model to the formation of a river-dominated delta and compare the model dynamics with observations of the formation of the Balize Lobe of the Mississippi River Delta. The model generates both subaerial and subaqueous channels and lateral levee formations as well as a profile morphology with steep drop-offs and a flat delta surface which is similar to natural ones. We show that the dimensionless parameters of the model may be consistently rescaled to match the Balize Lobe. This means that after rescaling the water flows, the subaerial geometry and time, the deposited (subaqueous) lobe volume, the sediment and water flows, the age, as well as the sediment capture ratio match the observed data. Finally, we use detrended fluctuation analysis to show that the modeled long-term dynamics of the delta formation process shows a complex temporal correlation structure. A characteristic time scale separates periods of consistent delta growth by gradual sediment deposition at the mouths of distributary channels from periods during which random large-scale channel avulsions lead to rapid change and the formation of new channels and subaqueous-dominated deposition.