Simulation of birdfoot delta formation with 1 application to the Mississippi

3 Recently a reduced complexity model which simulates the process of delta 4 formation on geological time scales has been proposed [Seybold et al., 2007]. 5 It includes subaerial and subaqueous growth in a three dimensional frame-6 work. In this paper we apply this model to the formation of a river domi-7 nated delta and compare the model dynamics with observations of the for-8 mation of the Balize Lobe of the Mississippi River Delta. We show that the 9 dimensionless parameters of the model may be consistently rescaled to match 10 the Balize lobe. This means that after rescaling, the subaerial geometry and 11 time, the deposited (subaqueous) lobe volume, the sediment and water flows, 12 the age, as well as the sediment capture ratio match the observed data. The 13 model generates both subaerial and subaqueous channels and lateral levee 14 formations as well as a profile morphology with steep drop offs and a flat delta 15 surface which is similar to natural ones. Finally we use detrended fluctua-16 tion analysis to show that the modeled long-term dynamics of the delta for-17 mation process shows a complex temporal correlation structure. A charac-18 teristic timescale separates periods of consistent delta growth by gradual sed-19 iment deposition at the mouths of distributary channels from periods at which 20 random large scale channel avulsions lead to rapid change and the forma-21 tion of new channels and subaqueous dominated deposition.