Stream Deposition
Bars
A ridge of sediment deposited in the middle or along the banks of a stream - Usually sand and gravel - Generally formed at the end of a flooding event, when flood waters recede and slow down, depositing sediment - Bar deposits can sometimes contain placer deposits- concentrations of heavy particles, such as gold, platinum, other metals or gemstones
Alluvial Fan
A stream coming into a desert form. No waves or tides. Usually snow melt going down mountains to the desert. Dumped right at the bottom of the mountain. Water soaks almost immediately because of flat dry land.
Stream Deposition
As velocity falls, largest particles settle out Results in sorting of sediment in river deposits, called alluvium Most transport takes place during floods and deposition as flood waters fall
Point Bar
Caused by erosion (outside) and deposition (inside). This eroding of land causes meandering streams
Braided Streams
Heavily loaded with sediment Sediment collects as bar deposits which separate the stream into several different channels
Oxbow Lake
Horseshoe shape that is completely cut off from the channel because of silt buildup
Meander cutoff
Land gets narrower and narrower until the erosion completely cuts through the land forming a circle
Distributaries
Main channel broken apart into smaller channels. Lots of sediment deposits
Meandering Streams
Older, well defined streams that tend to develop curves Faster on the outside (picks up material) Slower on the inside (deposited material) A "mature" river
Deltas
Sediment that accumulates at the mouth of a stream
Flood Plains
Sediments are deposited as a river floods its banks and the water velocity slows. - Most sediment is dropped closest to the river channel, with progressively less sediment carried away from the channel Organic rich material. Good for agriculture Years and years of buildup
Different Delta shapes
Stream-dominated deltas: long finger like sand bodies (Mississippi) Wave-dominated delta: seaward margin of consists of islands reworked by waves. Fan shaped. Sediments pushed out by tributaries but pushed back in by waves (creates islands) Tide-dominated deltas: continuously modified into tidal sand bodies that *parallel the direction of tidal flow* splotchy
Natural Levees
Type of Flood Plain Water goes up and over boundary, starts slowing immediately, deposits sediments, builds up from channel.