Water transport in Fourleague Bay is strongly influenced by the discharge of the Atchafalaya River and prevailing wind conditions. In three 50-h intensive surveys, we measured transport through the major inlets of the bay during the three major river discharge/weather regimes of the year: strong frontal passage, high river flow, and calm, low river flow. Wind stress caused significant changes in both transport and water levels. North winds, dominant during winter frontal passages, caused a net export of water. During the high river flow survey, southeasterly winds created an opposing hydraulic pressure gradient in the Gulf of Mexico, diverting river flow into Fourleague Bay. This resulted in an increase in water elevation and the inundation of adjacent marshes. We believe that this high-discharge, southerly wind condition is the major mechanism leading to sheet flow and sedimentation on the marsh. Calm, low-discharge conditions, typical of late summer, produced classic tidally-dominated circulation.