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Fluvial Systems

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					Fluvial Systems

    GPH 111
 Fluvial Processes Game Plan:
 What are FLUVIAL PROCESSES and do
  they fit within geomorphology?
 Observation of BASIC CONDITIONS and
  TYPES of fluvial processes through a
  small activity
 What CONTROLS fluvial systems to
  SELF REGULATE their channel?
 The future of the Mississippi River (Lab)
     What are Fluvial Processes?




 Collection of surface water into organized sequence
  of channelized forms whereby sediment is
  transported from the continents to ocean basins.
   Fluvial Processes within
       Geomorphology




Sierra Estrella Mountains
        and the Gila River
Hopefully we will see all this
     stuff happening?
 Drainage Basins
  and Stream
  Order
 Hortanian vs.
  Saturation
  overland flow
 Groundwater
  absorption
 Fluvial sediment
  transport and
  deposition
  How do drainage basins form?




                             2) Springs also initiate
                             drainage development.



                              Stream Order:
                                  Rill (1)
                                 Gully (2)
1) Sheetflow - eventually
                               Stream (3)
collects to allow drainage
                                 River (4)
development.
Sheetflow happens one of two ways…

 Hortonian -




 Saturation - The ground gets saturated
  and can’t absorb anymore water, leading
  to overland flow.
Groundwater absorption and
       streams…




More Tropical     More Arid
                   (Exotic)
     Sediment Transport…
 Overall grain size decreases in a
  downstream direction
 Moves in four ways - bed load, saltated,
  suspended, and solution
Fluvial Deposition - Mountains
 weather and erode, rivers then
 transport the debris to the sea.

                        The Amazon
                        River Delta
                        Brazil, South
                        America
 Can you see all this stuff happening?

 Drainage Basins and
         Stream Order
                          Before
        Hortanian vs.
   Saturation overland
                   flow
        Groundwater
            absorption
     Fluvial sediment             After
         transport and
            deposition
    The Longitudinal Profile!




Maintains an “Equilibrium       Gradient”
   Rivers only want the energy to transport
     their water and supplied sediment to
       ocean basins, and nothing more!
              Key Concepts!
Discharge - Amount of water flowing in a river

Base Level – Ocean or lake elevation

Sediment Load – Sediment transported

Vegetation – Along and within the channel

      Rivers only want the energy to transport
        their water and supplied sediment to
          ocean basins, and nothing more!
    How do rivers adjust over time?



Too Full! – Upset
passengers, not
                       Equilibrium - Just enough      Too Empty! – Upset
enough fuel or
                       fuel to carry planes full of   passengers, too much
flights to transport
                       passengers to their            fuel or too many
customers
                       destinations and nothing       flights to transport
                       more – Happy Company!          customers.



    Similar to an airline that tries to fill all
  seats for their flights, no MORE or LESS.
How do rivers adjust over time?
Channel Aggradation
               Massive sediment
               input leads to
               extreme
               aggradation.
               “Steepens channel
               to increase
               available energy”
            Channel Incision
 Commonly takes place through knickpoint
  retreat!!


                           “Lowers available
                           energy”




  Let’s go outside!!!
Channel Incision
       Channel Widening and
            Narrowing
 The role of width
  to depth ratios in
  fluvial energy
 Higher width to
  depth ratios the
  more energy loss
  to friction
  Channel Widening




Increase width to depth ratios…
   “Decreases available energy”
  Channel
 Narrowing

Decrease width
to depth ratios…
“Increases available
energy”
Lengthening and Shortening -
     Channel Meanders
                    Areas of maximum
                    velocity causes
                    erosion generating
                    meander bends
                    that move in a
                    downstream
                    direction
Lengthening and Shortening -
     Channel Meanders
Lengthening and Shortening -
     Channel Meanders




     Famous Oxbow Lake in the Making!
     Lengthening and Shortening -
          Channel Meanders




Channel develops more meanders – “Lowers available energy”
Channel develops less meanders – “Increases available energy”
              Key Concepts!
Discharge - Amount of water flowing in a river

Base Level – Ocean or lake elevation

Sediment Load – Sediment transported

Vegetation – Along and within the channel

      Rivers only want the energy to transport
        their water and supplied sediment to
          ocean basins, and nothing more!
How do rivers adjust over time?


                        Let’s do the
                        Lab!!!
What do rivers do?
            Things to Know:
 Hortanian versus Saturation overland flow
 Stream Order, drainage basins, drainage
  divide
 Types of fluvial sediment transport
 What is a river’s equilibrium gradient?
 What alters a river’s equilibrium gradient?
 How can river’s respond to channel
  change?
  Help: Chapter FS

				
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