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Geological science
Exam 3
RIVERS AND FLOODS
  1. What is a stream?
moving water, driven by gravity, that flows from higher to lower elevations, and is confined in a
channel.
  2. Compare turbulent vs. laminar flow.
LAMINAR FLOW: water moves in parallel lines, and individual lines maintain their velocities.   This is like the fountain in the Detroit airport, or when you GENTLY turn a faucet on so you get a clear stream of water.
TURBULENT FLOW: individual flow paths are not straight lines, and may change velocity within streams.   This is like when you turn the sink on REALLY HARD.   All rivers are to some degree turbulent (illustrated to an extreme degree with kayaking Mystery Moves).
  3. What 3 processes erode material in rivers?
Abrasion: water-borne particles physically break off pieces of other particles they come into contact with.
Turbulent flow: loosens and lifts material from stream bed using water pressure.   Also known as “plucking”.
Dissolution: chemical weathering of soluble material (minerals, etc. that dissolve into water)
  4. What transports the largest particles: bed load, suspended load, or dissolved load?  The smallest particles?
Bed load(L) sediment is bounced and rolled across the stream bed (usually larger clasts)
Suspended load:(S) sediment is suspended by the water and carried (medium/small clasts)
Dissolved load: material is dissolved in the water (sodium, potassium, calcite, sulfate, dissolved organic carbon, etc.)
  5. What is the difference between stream discharge and stage?
DISCHARGE: stream output.   This is calculated as the cross sectional area of the stream * water velocity, and represents the amount of water going by a point.   HIGHEST IN THE WORLD: Amazon: 200,000 cubic meters per second.   One day’s discharge would satisfy NYC’s water needs for 5 years!
STAGE: stream height.   Once water stage height is high enough to jeopardize human structures and safety, we are at flood stage

  6. Would you expect... [continues]

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