Factors Affecting Transportation of Sediments
Running water is the primary agent of erosion on Earth. Most running water is found in streams and rivers. There are many factors that affect the movement of sediments in a stream.
Parts of a river system- tributaries- feeder streams
Watershed- the land from which the water runs off into the streams
Channel- flow downhill
banks-edges or sides
bed- a channel that is below the water level
A stream channel becomes wider and deeper as it erodes it's banks & bed
Channel Erosion-The channel lengthens and branches out where run off enters the stream
Stream Load- The materials carried by the stream- fragments, dissolved minerals, etc
Suspended load- small particles that do not easily settle- The more velocity the less likely they are to settle.
Bed load- the larger materials that move but settle faster
Dissolved Load- those materials that dissolve into the water through chemical weathering
Discharge- the volume of water moved by a stream in a given time period.
Gradient (slope), discharge, and channel shape influence a stream’s velocity and the erosion and deposition of sediments. Sediments carried by a stream are almost always rounded due to the grinding action of the water on the rocks, a process called abrasion.
Streams are usually formed in V-shaped valleys; and deltas, flood plains, and meanders are results of what a stream can form.
The average velocity (speed) of a stream depends on its slope and discharge, which in turn can explain the carrying power of a stream. As the velocity of the stream water increases, the size of the particles carried in the stream also increases, a direct relationship.
Streams carry materials in 4 distinct ways:
Floatation, solution (dissolved particles), suspension (within the water profile), and bed load (bouncing and dragging along the stream bed.
See the graph in the Earth Science Reference Tables to explain particle size to stream speed.
STreams or rivers with low gradient often meander. Here bends and curves develop because the velocity of water decreases. Fast moving water seems to cut straight through and slow moving creates curves. However this creates erosion due to the energy directed toward the banks
Oxbow lakes form from meanders that leave areas cut through
Braided streams- a single channel that divides into multiple channels.