This paper reports a reconnaissance level study of a storm surge barrier in the Mississippi River. Historical hurricanes have shown storm surge of several meters along the Mississippi River levees up to and upstream of New Orleans. Future changes due to sea level rise and subsidence will further increase the risk of flooding due to hurricane storm surge. A surge barrier downstream of New Orleans has been considered as an alternative to levee raise along the Mississippi River. Hydraulic computations show that the build-up of water behind the barrier due to the Mississippi River flow is (much) lower than the hurricane surge protruding up the river in the no-barrier situation. The barrier will probably eliminate the need to upgrade the system upstream of the barrier while providing the same level of hurricane risk reduction. A hybrid barrier (a combination of different gate types) with a primary swing gate for navigation (and flow) and secondary lift gates to accommodate for flow is a technically feasible alternative. The barrier remains open for almost the entire year and would only to be closed during severe tropical events (say once every 2 - 3 years). Several measures are included in the conceptual design to mitigate the navigation impact. The construction costs of the barrier are estimated at $1.6 - 2.6 billion. It is recommended to compare the investment costs of a barrier including adjacent tie-ins to the existing HSDRRS to the costs of upgrading and maintaining the levee system throughout the city of New Orleans.