Velocity Gradient – rise over run Channel shape Channel roughness Discharge – amount of...
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Transcript of Velocity Gradient – rise over run Channel shape Channel roughness Discharge – amount of...
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Factors affecting erosion and deposition
Velocity Gradient – rise over run Channel shape Channel roughness Discharge – amount of water flow per
unit time, as discharge increases, load increases.
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Velocity
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Velocity
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Channel shape and roughness
SemicircularFlow fast
Wide channelFlow slow
Rough bottomFlow slow
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Channel shape and roughness
Narrow channelFlow fast
Wide channelFlow slow
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Changes from Upstream to Downstream
Profile Cross-sectional view of a stream Viewed from the head (headwaters or source) to the mouth of a
stream Profile is a smooth curve Gradient decreases downstream
Factors that increase downstream Velocity Discharge Channel size
Factors that decrease downstream Gradient Channel roughness
Stream Erosion• Stream erosion (and deposition) controlled by flow velocity and discharge
– Stream velocity controlled by stream gradient (slope), channel shape and channel roughness• Maximum velocity near center of channel
– Floods involve increased velocity and discharge (volume of water passing a particular point in a stream over time)
• Higher stream velocities promote erosion and transport of coarser sediments
– Erosion of very small particles difficult due to molecular binding forces
Do Now
Do ES1301-How Does Stream Flow Change over Time?
This activity can be found on my website under “Files From Class.”
Monday, April 29, 2013
Objective #2 You are going to learn the similarities and
differences between deltas and alluvial fans
DEPOSITION
Definition
Deposition- the process in which sediment is laid down in new locations The end result of erosion
Water Deposition
Alluvial fan- fan shaped deposit of sediment on land Usually form when a stream slows down and
enters a flat plain Delta- sediment from a stream deposited
where a river enters a large body of water Triangular shape
Alluvial fan and Delta
Sediment Deposition• Delta - body of
sediment deposited at the mouth of a river when flow velocity decreases– Surface marked by shifting distributary channels
– Shape of a delta depends on whether its wave-dominated, tide-dominated, or stream-dominated
Sediment Deposition• Alluvial fan - large, fan- or cone-shaped pile of sediment that forms where stream velocity decreases as it emerges from a
narrow mountain canyon onto a flat plain
– Well-developed in desert regions, such as the southwestern U.S.– Larger fans show grading from large sediments nearest the mountains to
finer sediments farther away
DO NOWNow you should access ES104 from the
“Files From Class” section of my website. This investigation will focus more on
deltas.