Fig' 25'10

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Fig. 25.10
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Fig. 25.9
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Fig. 25.11
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Fig. 25.8
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Fig. 6.01
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River systems have a collection system,
transporting system, and distribution
system. Rivers both erode (carry sediment away)
and deposit sediment depending on flow velocity.
Places of erosion and deposition vary along the
whole system.
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Fig. 6.02
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Fig. 11-2, p.269
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Fig. 11-6, p.271
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Fig. 11-29, p.283
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Fig. 6.06
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Fig. 6.09
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Fig. 11-22, p.280
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Fig. 6.11
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Fig. 11-19b, p.279
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Fig. 6.06
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Fig. 6.04
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Fig. 11-14, p.275
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Fig. 6.07
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Fig. 6.08
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Fig. 11-18, p.278
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Fig. 11-20a, p.279
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Fig. 11-20b, p.279
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Fig. 6.10
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Fig. 6.11
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Stream Erosion

• Downcutting
• Headward Erosion

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Fig. 11-9, p.273
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Fig. 6.02
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Fig. 11-2, p.269
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Discharge

• The volume of water moving through a channel with
  time.
• Discharge Volume per time Q V / t
• Discharge velocity x cross sectional Area
• Q v A

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Fig. 6.03
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Discharge and Erosion

• Carrying Capacity the amount of sediment a
  stream CAN carry.

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Measuring Discharge

• QvA

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Fig. 6.03
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Average velocity varies

• across the channel
• and with depth

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Discharge-Stage rating curve

• Getting Q measurements quickly

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Factors affecting stream velocity

• Water depth (hydraulic radius)
• Slope
• Channel bottom roughness

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Deeper, Steeper, Smoother Faster

• Deeper water (larger hydraulic radius, R)
• Note the larger the radius, the smaller the
  wetted perimeter relative to the cross
  sectional area, thus lesser the relative channel
  friction P / A 2 p r / p r 2 2 / r
• Steeper channel (larger slope, s)
• Note slope is gradient, s, is the drop in
  elevation with distance down the channel.
• Smoother channel (smaller Manning roughness
  coefficient, n)
• Note friction, n, is large for rough channels,
  small for smooth channels

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Discharge increases downstream, so

• Q v A v l w
• Which variable gets bigger?
• v, velocity
• l, channel depth
• w, channel width
• Answer all of the above

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Fig. 6.05
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The discharge hydrograph

• Example of seasonal response

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Flooding

• The discharge hydrograph
• Hydrograph response with
• Basin size
• Distance downstream
• collection system, transport system,
  distribution system
• Infiltration capacity
• (Note well discuss different responses to
  infiltration capacity together with ground water
  baseflow later)

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Flooding

• Drainage basin size, distance downstream, and the
  time of flood crest

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Fig. 6.16
Affect of Basin Size
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Fig. 11-30, p.284
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Flooding

• Collection system flooding and the effect of
  infiltration capacity
• Infiltration Capacity ability of the
  landsurface to allow ground-surface water to
  infiltrate (soak in)
• Reduced IC causes increased runoff, and thus
  increases flash flood hazard!!

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Flooding

• Collection system (small basin)

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Fig. 6.13
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Flooding

• Large basin (transport system)

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Fig. 6.01 p.139
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The Natural Levee
Fig. 11-21, p.280
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Fig. 6.14
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Fig. 6.18
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Flooding

• Distribution system flooding

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Fig. 12-17, p.306
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Fig. 12-19, p.307
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Fig. 12-22, p.309
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Fig. 12-21, p.308
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Flooding

• Predicting floods

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Fig. 11-42, p.290
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Fig. 6.17
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Baseflow

• The background flow in a river provided by ground
  water

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Fig. 11-28, p.283
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Baseflow

• Ground water system moderates floods by storing
  water.
• Flood response to infiltration capacity discussed
  previously
• (higher infiltration gt increased ground water
  moderation of floods)

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Infiltration Capacity

• Flood affect of Urbanization
• Flood affect of Farminization (agriculture)

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Fig. 6.21
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Fig. 6.22
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Controlling Flooding
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Dams
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Fig. 14.25
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Fig. 6.27
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Fig. 6.28
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Retention Ponds
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Fig. 6.24
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Levees
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Fig. 6.25
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Fig. 12-1, p.298
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Channelization
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Fig. 11-19b, p.279
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Fig. 12-16, p.305