Classification[edit]Sediment can be classified based on itsgrain sizeand/or its composition.Grain size[edit]Main article:Particle size (grain size)See also:soil textureandUnified Soil Classification System

Sediment in theGulf of Mexico

Sediment off theYucatn PeninsulaSediment size is measured on a log base 2 scale, called the "Phi" scale, which classifies particles by size from "colloid" to "boulder". scaleSize range(metric)Size range(inches)Aggregate class(Wentworth)Other names

< -8> 256mm> 10.1 inBoulder

-6 to -864256mm2.510.1 inCobble

-5 to -63264mm1.262.5 inVery coarsegravelPebble

-4 to -51632mm0.631.26 inCoarse gravelPebble

-3 to -4816mm0.310.63 inMedium gravelPebble

-2 to -348mm0.1570.31 inFine gravelPebble

-1 to -224mm0.0790.157 inVery fine gravelGranule

0 to -112mm0.0390.079 inVery coarsesand

1 to 00.51mm0.0200.039 inCoarse sand

2 to 10.250.5mm0.0100.020 inMedium sand

3 to 2125250m0.00490.010 inFine sand

4 to 362.5125m0.00250.0049 inVery fine sand

8 to 43.962.5m0.000150.0025 inSiltMud

> 8< 3.9m< 0.00015 inClayMud

>10< 1m< 0.000039 inColloidMud

Composition[edit]Composition of sediment can be measured in terms of: parentrocklithology mineralcomposition chemicalmake-up.This leads to an ambiguity in whichclaycan be used as both a size-range and a composition (seeclay minerals).Sediment transport[edit]

Sediment builds up on human-made breakwaters because they reduce the speed of water flow, so the stream cannot carry as much sediment load.

Glacial transport of boulders. These boulders will be deposited as the glacier retreats.Main article:Sediment transportSee also:Rouse numberSediment is transported based on the strength of the flow that carries it and its own size, volume, density, and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, while larger or denser particles will be more likely to fall through the flow.Fluvial processes: rivers, streams, and overland flow[edit]Particle motion[edit]Rivers and streams carry sediment in their flows. This sediment can be in a variety of locations within the flow, depending on the balance between the upwards velocity on the particle (drag and lift forces), and thesettling velocityof the particle. These relationships are shown in the following table for theRouse number, which is a ratio of sediment fall velocity to upwards velocity.

where is the fall velocity is thevon Krmn constant is theshear velocity

Hjulstrm curve: The velocities of currents required for erosion, transportation, and deposition (sedimentation) of sediment particles of different sizes.Mode of TransportRouse Number

Bed load>2.5

Suspended load: 50% Suspended>1.2, 0.8,