Chapter 13 Surface Water

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Chapter 13 Surface Water
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Chapter 13.1
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Streams and Rivers

• Carry over half of all water that falls on
  Earths surface to the ocean and almost all
  erosion.

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River Systems

• Tributary stream that runs into a large stream
• Beaver is a tributary of the Ohio
• River System a river and all of its tributaries
• Drainage Basin (watershed) includes all the
  land that drains into the river

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• Divide highland that separates one drainage
  basin from another
• Rocky Mountains the major Western divide for
  the Mississippi river. Rain falling on the
  Eastern side flows to the Mississippi on the
  Western side to the Pacific

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Characteristics of Streams and Rivers

• Controlled by velocity, gradient and shape of
  channel
• Velocity distance the water travels in a given
  amount of time
• Faster it moves the more material it can carry
  and the larger the size of the material

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• Gradient steepness of the slope of a stream
• Discharge the amount (volume) of water that
  passes a certain point in a given amount of time
• The streams that feed the stream the higher the
  discharge (downstream)
• Rain and melting snow may also add to discharge
  increasing the streams velocity

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• Channel the path the water flows
• A wide winding channel will slow the water down
  due to friction
• A straighter deeper channel will have less
  friction therefore a higher velocity

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Chapter 13.2
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Stream Erosion and Deposition

• Running water is the most effective agent of
  erosion.

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How streams weather and erode material

• Rapidly flowing water can lift, split off and
  move rock
• Abrasion is the most effective form of erosion.
  The stream uses sand, pebbles and boulders as
  cutting tools.
• The cut banks and beds of rivers and round
  themselves in doing so
• Potholes sand pebbles and boulders swirl in
  whirlpools grinding out a hole in the streams
  bed.
• Limestone and marble most easily eroded by rock

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How streams transport material

• Load soil and rock material being transported
  by the stream
• Solution (dissolved load) most comes from
  groundwater entering the stream
• Suspension turbulence keeps material supported
  in water cause the water to look muddy
• Bed load material that is too heavy to be
  carried in solution travels on the floor (bed)

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• Competence is a measure that describes the
  maximum size of the particle a stream can carry
• Capacity is a measure of the total amount of
  sediment a stream can carry
• Velocity controls both the higher the velocity
  the larger the competency
• During floods sand and pebbles can be carried in
  suspension this when most of the streams erosion
  is done

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Stream Deposition

• Deposition (dropping of load) occurs in a stream
  when its velocity or discharge is decreased
• The greatest decrease in a rivers velocity occurs
  when it empties into a sea or lake. All sediment
  will deposited

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Depositional features

• Delta fan shaped deposit that forms when a river
  flows into a quiet or large body of water
• Small current and waves along with a large amount
  of sediment helps deltas to form
• Distributaries branches in the delta that
  distributes sediment
• Alluvial fan form at the base of a steep hill
  in a dry region

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Chapter 13.3
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River Valleys

• Begins as a gulley which grow in length, width
  and depth every time it rains
• When it cuts deep enough to hit the ground water
  it becomes a stream
• Headward erosion stream lengthens above its
  headwater

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Canyons and v-shaped valleys

• Canyons form when the river cuts into its bed
  rapidly or when the rock materials on the side of
  the canyon are resistant to erosion.
• Rock type will affect the speed of cutting also
• V-shaped valleys describe youthful valleys
• No large bends will exist
• V-shaped comes from the exposed walls being
  eroded by longer amount of time

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• Base level lowest level a stream can erode to
• Controlled by what the stream flows into
• Closer to base level the lower the gradient and
  sideways erosion occurs
• Stream Piracy through headward erosion, one
  river wears through the divide and captures the
  headwaters of the other river

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Rapids and Waterfalls

• Rapids are formed by the recession of waterfalls
• Waterfalls are reduced by undermining
• Undercut the waterfall which eventually falls

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Chapter 13.4
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Flood plains and Floods

• Flood when a river overflows it banks the part
  of the valley floor it covers is the flood plain

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Features of a Flood plain

• Reasons why a river near base level meanders
  (bends)
• River current is more easily deflected because of
  a lower velocity
• Erosion is more dominate on the outside of the
  bend
• Oxbow lake curved body of water formed when the
  river cuts off a bend
• Levees build up of sediment along the river
  bank formed floods when the slower water deposits
  material

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Floods

• Deposit minerals and nutrients on flood plains,
  making the area fertile for agriculture
• Flash floods occur on small narrow streams during
  heavy downpours
• Floods on large rivers occur due to large amounts
  of rain of long periods of time

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Flood Prevention and Control

• Plant vegetation to control runoff
• Dams
• Artificial levees walls built alongside a
  stream
• Spillways channel built parallel to the main
  channel in the back swamp to divert water