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Rivers

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					KEY TERMS FOR RIVERS
Vocabulary for Notes (use wherever there is a ______________________)

Abrasion              Drainage divide                   Saltation
Aggradation           Floodplain                        Sand sized
Alluvium              Greater                           Solution
Base level            Hydraulic force                   Terrace
Bedload               Interconnectedness                Turbidity
Clay sized            Larger                            Watershed
Climate               Meandering Stream
Cut bank              Point bar
RIVERS

                       Objectives: To Successfully be Able to Explain:

                       1.   The processes of stream erosion, transportation, and deposition
                       2.   The origin and characteristics of river landforms.
                       3.   The concept and importance of a watershed.



   Misconceptions:

   1.   Only the Nile River flows north.
   2.   Stream velocity decreases as one approaches base level (ocean or lake).
   3.   Tornados will not strike between two rivers.
   4.   Groundwater flows in underground rivers
   5.   Rivers and groundwater are separate.
   6.   Excluding the oceans, there is more river water than groundwater.
   7.   Water from natural springs is safe to drink.
   8.   All rivers empty into lakes, seas, or oceans.

        Did you Know?

             1. The Chicago River is colored green on St. Patrick’s Day?
            2. The Chicago River’s flow was reversed in 1900 for sanitation reasons?
   3.   Along the Detroit River is one of the very few places where you look south into Canada
        from the lower 48 states.
   4.   A river horse is a hippopotamus, and that a river jack is an unpleasant-looking snake, the
        African puff adder
   5.   The Congo River is the longest river that flows generally westward?
   6.   The Missouri-Mississippi is the longest river flowing generally southward?
   7.   The Yangtze is the longest eastward flowing river?
   8.   The Nile is the world's longest northward flowing river?
   9.   Saudi Arabia has no natural rivers?



Tying it all together: Climate determines the size and discharge of rivers but some rivers are
termed exotic, not because of their sinuous curves but because exotic rivers, like the Nile River
          are able to maintain flow through arid regions because it originates in rainy regions.
          The bedrock or regolith upon which rivers flow determines the form the river takes
              across the landscape. Differences in bedrock resistance or the presence of faults will
               channel rivers along fairly predictable paths. Where little difference exists in
bedrock, rivers will establish a dendritic (birds foot) pattern. Rivers are the most important agent
of landform development, greater than the erosion and deposition produced by wind, glaciers,
waves, or mass wasting. Even in the desert, the occasional rainfall on unprotected slopes
produce significant landform development. Rivers are an important part of the biosphere,
supplying food, providing an avenue for transportation, serving as a source of potable water, as a
source of cooling water for industry, and as a means to disperse waste and sediment eroded from
the surrounding watershed.

OBJECTIVE 1: The processes of stream erosion, transportation, and deposition.

The form of a river or stream is determined in part by _______________, slope, discharge, and
underlying bedrock .

            In the space below supply your best guess how a rock carried by a river would
                change as it moves from the mountains to its final resting place in a river delta.
                 View Erosion animation showing rocks carried by the river are gradually
worn down as they travel downstream to find out.




As you have outlined, river form will be determined by the factors discussed above. The tools
allowing these factors to shape a river are erosion, transport, and deposition.

        A. Stream Erosion

       ___________________ grinding of the river bed due to particle friction.

       Solution: rock and sediment become dissolved within the water column.

       ________________________ the force or weight of the water striking the river bed
       results in erosion. Hydraulic force results in a type of plucking that can pry loose weak
       rock and sediment.

   By these processes rivers grow deeper and wider

   Over time ___________ shaped valleys form in steep terrains



   B. Stream Transport
   __________________ sediment in contact with the bed carried downstream by stream
   flow.

   __________________________ the downstream bouncing motion of sediment in which
   sediments are dislodged from the stream bed, suspended for a short distance, and then fall
   back to the stream bed. Sediment impact will often dislodge other sediments, beginning
   the process over again.

   Rolling: Rock or sediment that rotates across the surface of the river bed. At all times
   the body is in contact with the river bed.

   ______________________ dissolved sediment held within the water column.

   Suspension: visible sediment carried within the water column. Excessive amounts of
   suspended sediment results in increased water cloudiness or _____________________.
   Turbidity decreases light penetration, reduces photosynthesis, buries spawning beds, and
   allows contaminants to be transported on suspended sediment.

C. Stream Deposition

   _________________________ the deposition of sediment by streams when the quantity
   of material carried by the stream is greater than the competence or ability of the stream to
   carry its current load of sediment.

   ____________________ any sediment deposited by streams. The following animation
   shows the buildup of sediment in a delta.

   Discharge and Deposition: the ________________the discharge, the _____________ the
   ability to carry material through suspension and through bedload. When discharge
   declines, aggradation will occur.

   Discharge and Sediment Size: the ________________ the discharge the greater the
   ability or competence of the stream to carry _______________ sediment sizes. Boulders
   will be moved when discharge is greatest, only clay sized particles will be moved when
   discharge is low.
OBJECTIVE 2: The origin and characteristics of river




landforms.




(Images: http://www.uwsp.edu/geo/courses/geog391/toriv/images%5Clandform.gif)



__________________ a plain next to a river and prone to flooding. This animation shows the
formation of the floodplain.

Bluff: a steep, prominent slope originating from river erosion.

  _________________ a flat, narrow stretch of ground, often having a bluff face facing the river.
  Terraces often represent former floodplains that were left stranded at a higher position when
the river down cut to a lower level.

Natural Levee: An elevated bank of alluvium bordering a river. The bank is deposited when the
river leaves behind much of its load during flooding.

___________________________ a stream having a pattern of snake like turns.
______________________ the outer portion of a river meander, usually steep, which is
continually undergoing erosion.

_________________________ a gentle-sloped, wedge-shaped deposit of alluvium on the inner
portion of a meander.

Thalweg: The deepest portion of the stream’s channel produced by faster moving, erosive stream
flow.



              In the space below, draw a meander and where to navigate a canoe




Meander Neck: a narrow isthmus of land separating two adjacent meanders.

Oxbow Lake Formation: A portion of a meander, now a lake, which has been cut off from the
original river channel. Oxbow lakes became isolated from the original channel as a river cuts
through a meander neck to shorten its course, blocking off the old channel. The new river
channel then migrates away from the lake. Eventually, oxbow lakes silt up to form wetlands and
finally meander scars.

                    Based on this animation of oxbow lake formation, draw a two to four step
                    diagram illustrating how oxbow lakes form. Here is another view of the
                 oxbow lake formation processes.



OBJECTIVE 3: Concept of a watershed.




                                          ___________________________: an area of land
                                          where surface water and groundwater drain to a
                                          common point; depending on the scale, watersheds
                                          can range in size from a few acres to thousands of
                                          square miles. Watersheds can and do often cross
                                          county, state, and national boundaries.      (Image:
http://www.soque.org/About%20the%20Soque/watershed%20pic-smaller.GIF



             READ NO FURTHER. In the space below, write a short paragraph highlighting
              the implications of watersheds crossing county, state, and national boundaries.




Think of a watershed as a type of topographic funnel: all surface and groundwater within the
watershed is channeled toward a lower point in the watershed, eventually reaching the
watershed’s _____________________ (lowest level to which a stream can erode), whether it be
a pond, river, lake, sea, or ocean.

___________________________: Each watershed or drainage basin is separated topographically
from adjacent watersheds by a high point, which could be a ridge, hill, or mountain.

Formation: Many watersheds are formed by tectonic or volcanic processes that deform the
Earth’s crust through folding, faulting, or down warping. Watersheds can also result from
differential erosion by wind, water, or ice. The structure and strength of the underlying rocks
influence the where erosion occurs, with valleys typically consisting of less resistant rock and
hills consisting of more erosion-resistant rocks.

The Concept of ______________________: all life forms within the watershed are linked by
dependence on the same source of surface or groundwater. Pollution in one part of the watershed
can impact water quality in another part of the watershed. Sources of pollution are indeed varied.

_____________________ pollutants settle out fairly quickly and may only impact water quality
a short distance from the discharge point.

_____________________ pollutants and pollutants in solution can be carried for hundreds of
miles from their discharge point, contaminating the water supply of city residents that had
nothing to do with the original source of pollution.




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