Stream Erosion & Transport

Stream Velocity

Stream Gradient

Discharge

Channel Shape

Four Main Factors of erosion and transportation of a stream:

Stream Velocity

Faster streams = more energy

Carry large particles

Fast streams erode beds by abrasion

Velocity is affected by stream’s steepness, discharge, & shape of stream channel

Stream Gradient

Steep vs. gentle gradient

Water flows faster on steeper slopes

Discharge

Amount/volume of water flowing past a point in a stream over a certain period

Usually increases downstream as other streams add more water

Not constant, varies with seasons

Greater discharge = greater stream velocity (direct relationship)

Erosion occurs during floods when stream discharge & water velocity both increase

Channel Shape

Size & shape affect stream velocity & discharge

Shallow = slower flow of water, more water is slowed due to friction with stream bed

Deep = faster flow of water due to no friction with stream bed

Solution

Suspension

Bed Load

3 ways of Transportation of materials

Solution

Dissolved minerals that were chemically weathered out of bedrock

Not visible

Suspension

heavier materials than water (clay, silt, sand)

Turbulence of flowing water stir materials, materials do not sink & remain suspended in water

Faster streams = carry more material

Caused muddy appearance to streams

Most materials = transported in suspension

Bed Load

Too heavy materials, can’t be carried in suspension

Sediments roll, slide, bounce along bottom of stream channel

Sediments move this way by abrasion

larger, first

As stream velocity decreases _____ particles are deposited _____

round, Faster

_____ particles settle _____ than flat particles because there is less friction with the water.

Vertical Sorting

Larger particles on the bottom, smallest at the top

Deposition caused by continually decreasing stream velocity

Graded bedding

decreasing grain size upward through bed indicating deposition from waning current

Caused by stream velocity overtime

• Floods

• Seasonal

Horizontal sorting

Larger particles deposited near mouth of stream

Smaller particles deposited farther out in body of water

Deposition caused by decrease in stream velocity as stream enters large body of water

Particle size affects type of sedimentary rock that forms