The Lafourche Delta network in the Mississippi Delta Complex

Abstract:

The formation of the branching channel network is controlled mainly by water discharge and the boundary shape of receiving basin. The understanding of channel morphology is important because it controls the sediment diversion in a river delta, and determines the sustainability of coastal zones. Numerical models of river deltas have improved remarkably over the past two decades. However, the long-term (millennial scale) simulation of real delta systems remains rare. Here, we attempt to reconstruct the Lafourche Delta channel network, active 1600-600 years before present, with a numerical model (Moving Boundary Model for Distributary Channel Networks MB_DCN). Basin shape scenarios were set up on the basis of paleo-shoreline and channel structure, and water discharge scenarios were estimated based on the reconstruction of North American basin river discharge rate after the Last Glacial Maximum period. Runs with 6 boundary shapes and 2 river discharge scenarios show that each scenario produced distinguishing channel characteristics including a complex channel network, diverse progradation rates and channel numbers, and number of bifurcations. For the appropriate basin shapes, reasonable water discharges and common sediment transport parameters, MB_DCN produces a channel network that resembles the Lafourche Delta channel network morphology and progradation rates. Radially symmetric grow pattern can also be partially controlled by the boundary shape and water discharge. Our preliminary results suggest that the basin boundary shape and water discharge are the most important control of the distributary channel network in terms of morphological aspect.