When looking at this map and seeing the jumble of ancient riverbeds – imagine all those shifts sped up: the Mississippi is like a shifting snake, twisting to find its easiest way down to the Gulf. These shifts occur every thousand years or so, especially in the lower parts of the river, through a process known as delta switching, or avulsion: when the river flow is slow, the sedimentation clogs the river channel and it eventually finds another channel. This process is by no means ‘historic’ (i.e. ‘over’) – from the 1950s onwards, the US government has worked on the Old River Control Structure, meant to prevent the Mississippi from switching to the Atchafalaya River channel.
