Alluvial fans'

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Sediment removal
Grand Canyon Running water is capable of moving
a lot of material, eroding the land.
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Flooding in Mozambique, spring 2000
When rivers flood the water slows down and the
sediments they carry are spread over the flood
plain
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• Sediment is eroded by rivers. This sediment is
  transported by the energy of the running water.
  It accumulates in places where the energy of the
  running water is dissipated either
• by evaporation of the water
• by mixing of the running water with a large body
  of standing water (lake, ocean).

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When a river floods, coarser (heavier) material
transported by the river is deposited close to
the river channel. Fine material accumulates
further away on the flood plain. This results in
the build up of natural levees - higher banks
right along the river channel.
Natural levees
Meanders of the Red River at Selkirk during 1997
flood, Manitoba
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Alluvial fans.
An alluvial fan is a low conical river deposit
which forms where a watercourse, coming from a
steep valley, suddenly reduces its speed and
dumps its sediment load where it debouches onto
the flatter ground of a lowland. These fans have
so much sediment that they are building out into
the path of the main lowland river.
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Sediment transported to the shore by the
Mississippi River is deposited in a delta. This
is an accumulation of sediment that piles up at
the mouth of a river. This material is also
further moved along the shore by longshore
currents.
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As clastic sediment is delivered to the ocean,
the coarser material settles close to the river
mouth. Finer material is washed farther out into
the ocean. Limestone that forms mostly from
shells of organisms accumulates far from any
supply of clastic sediment.
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Once sediments reach the ocean they settle.
Finer sediments settle more slowly and thus can
be transported by longshore and ocean currents.
Flood runoff in the aftermath of Hurricane Floyd
carried an immense load of sedimentincluding
soil, sand, sewage, fertilizer and
pesticidesinto the sea. This image, taken on
September 23, 1999, shows the sediments being
swept into the Atlantic by the Gulf Stream.
(Image courtesy SeaWiFS Project, NASA GSFC)
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The largest accumulations of sediment in the
ocean (red and yellow) are where there are major
sediment delivery systems such as large rivers or
significant coastal deserts where wind may blow
sediment into the ocean.