The delta of the Mississippi River is in jeopardy. It is rapidly subsiding into the Gulf of Mexico. Delta marshland is being drowned and the shoreline is moving northward toward New Orleans. The cause of these problems is the levee system along the Mississippi River, which prevents the replenishment of sediment to the delta. One way to restore the delta is through the use of one or more controlled partial avulsions of the Mississippi River. The design of such diversions represents a monumental task. A natural example of an avulsion in the Mississippi Delta, however, offers an excellent opportunity to test the concept of land building via river diversions. The Atchafalaya River is a distributary of the Mississippi River. During the flood of 1973, part of the Atchafalaya River avulsed into a man-made channel. The Wax Lake Delta at the mouth of the channel has been building seaward since then. Here a morphodynamic model of the Wax Lake Delta is presented and tested against field data. While the model is preliminary, the fact that it captures the process of land building at the Wax Lake Delta suggests that it can be adapted to the design of a major controlled partial avulsion of the Mississippi River into, for example, Barataria Bay.