Part 8 ALLUVIAL FANS and DELTAS

Classic alluvial fan. Fans often develop where confined channels on steep gradients suddenly emerge from their canyons, changing the flow regimen sufficiently to stimulate deposition.

River deltas are commonly built off a series of anastomotic distributary channels, such as that shown at lower right

The Mississippi and Atchafalaya Rivers have deposited enormous deltas over the past 6000 years; Delta # 7 being the youngest and #1 the oldest.

Abandoned distributaries of the Mississippi and Atchafalaya Rivers. The Metairie Ridge distributary channel, separating lower and upper New Orleans, is shown in red

Until the construction of jetties in the late 1870s, sand bars closed off the mouth of the Mississippi River each year for as much as 3 months at a time following high flows.