Date post: | 20-Dec-2015 |
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ALLUVIAL FANS ALLUVIAL FANS and DELTASand 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.