Laying the Groundwork

Moreover, man-made underwater jetties at the mouth of the Mississippi confine and accelerate the river's flow, preventing silt build-up at the river's mouth from blocking ships, instead jettisoning it into deep Gulf waters. By contrast, levees confine the Atchafalaya at only a few populated sections along its route, and the river remains unfettered at its mouth, where it slowly builds new wetlands over a wide area of shallow Gulf water.