that the stream carries. As groundwater leaches through layers of soil and rock, minerals
dissolve and are carried away. Groundwater contributes most of the dissolved components
that streams carry. Once an element has completely dissolved, it will likely be carried to
the ocean, regardless of the velocity of the stream. In some circumstances, the stream water
could become saturated with dissolved materials, in which case elements of those minerals
might precipitate out of the water before they reach the ocean.
Another way that rivers and streams move weathered materials is as thesuspended load.
These are pieces of rock that are carried as solids as the river flows. Unlike dissolved load,
the size of the particle that can be carried as suspended load is determined by the velocity
of the stream. As a stream flows faster, it can carry larger and larger particles. The larger
the size particle that can be carried by a stream, the greater the stream’scompetence.If
a stream has a steep slope orgradient,it will have a faster velocity, which means it will
be able to carry larger materials in suspension. At flood stage, rivers flow much faster and
do more erosion because the added water increases the stream’s velocity. Sand, silt and clay
size particles generally make up the suspended load for a stream (Figure10.2). As a stream
slows down, either because the stream’s slope decreases or because the stream overflows its
banks and broadens its channel, the stream will deposit the largest particles it has been
carrying first.
Figure 10.2: Rivers carry sand, silt and clay as suspended load. During flood stage, the
suspended load greatly increases as stream velocity increases. ( 30 )
The last way that rivers and streams move weathered materials is asbed load.This means
that although the water in the stream is capable of bumping and pushing these particles
along, it is not able to pick them up and carry them continuously. Bed load is named for
the fact that these particles get nudged and rolled along the stream bed as the water flows.
Occasionally a larger size particle will get knocked into the main part of the stream flow,