Rivers and streams carry small solid particles of rock and mineral downhill, either suspended in the water column ("suspended load") or bounced, rolled, or slid along the river bed ("bed load"). Solid particles are classified according to their mean diameter from smallest to largest as clay, silt, sand, pebble, cobble, and boulder. During low velocity flow, only very small particles (clay and silt) can be transported by the river, whereas during high velocity flow, much larger particles may be transported, as documented in the table below.
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Diameter of objects moved (mm)
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Speed of current (m/sec)
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Classification of Objects
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|
0.2
|
0.10
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Mud
|
|
1.3
|
0.25
|
Sand
|
|
5
|
0.50
|
Gravel
|
|
11
|
0.75
|
Coarse Gravel
|
|
20
|
1.00
|
Pebbles
|
|
45
|
1.50
|
Small Stones
|
|
80
|
2.50
|
Large stones (fist sized)
|
|
180
|
3.50
|
Boulders
|
a. Plot the log of diameter against the log of the speed.
b. Find the best-fitting line using least squares regression on the log-transformed data.