Surface Water

1

• Surface Water

2
Streams and Rivers

• Over 50 of the water that falls to Earth ends up
  in a stream or river.
• Streams and rivers account for most of the
  erosion at the Earths surface.

3

• A River System consists of a river with all of
  its tributaries.
• Tributary A stream that runs into another
  stream or river.
• A rivers drainage basin or watershed includes
  all the land that drains into the river either
  directly or through its tributaries.

4
Four Factors Affect How a River Erodes and/or
Transports Sediment

• 1 Velocity
• The distance water travels in a given amount of
  time.

• Velocity is affected by three factors
• Slope of the riverbed
• Amount of water
• Shape of the riverbed

5
2. Gradient The steepness of the slope of a
stream or river.
6

• 4. Channel
• The path or physical depression the water flows
  through.
• The size and shape of a channel affect its
  velocity.

• 3. Discharge
• The amount of water that passes a certain point
  in a given amount of time.
• Discharge fluctuates depending on where it is
  measured i.e. above or below tributaries and
  the time of year.

7
Erosion and Deposition

• As streams flow, they erode rocks and soil,
  transport these sediments over long distances,
  and deposit them in areas of quieter water.
• Fast-moving water lifts and moves apart rock
  fragments as abrasive particles carried by the
  water cut away at bedrock.

8
Erosion

• Occurs when running water abrades its bed and
  walls using sand, pebbles and boulders from its
  bed load.
• Forms features, such as this pothole formed in
  the Susquehana River in Pennsylvania

9
Transport

• Materials are carried three ways
• Solution Dissolved particles
• Suspension Particles are kept from sinking by
  turbulence.
• Bed load Carried along the river bed
  (bouncing/rolling)

10
A streams ability to transport materials is
classified two ways

• Competence
• The maximum size of particles a stream can carry

• Capacity
• The total amount of sediment a stream can carry.

11
Types of load

• 1. Suspended load - finer sediment (usually clay
  and silt) suspended by turbulence in the flow
  (does not contact bed).
• 2. Solution load - dissolved rock carried in the
  flow
• 3. Bed load - coarser sediment (sand gravel)
  that slides, rolls or skips along the stream bed

12
Bed Load Diagram
13
Deposition

• Materials transported by rivers and streams are
  deposited when either their velocity or discharge
  changes.
• Beaches and sandbars can occur in streams and
  rivers as well as in oceans.
• Deltas and alluvial fans are excellent examples
  of deposition by rivers and streams.

14

• Delta
• Fan shaped deposit that forms when a river flows
  into a quiet or large body of water.
• Forms of fine sediments in water

15

• Alluvial Fan
• Forms when a steep mountain stream drains into
  dry level land at the base of the mountain.
• Forms of coarse sediments on dry land

16
(No Transcript)
17
O.K., so far weve learned. . .

• A river system consists of a river and all its
  tributaries, which are found within the rivers
  watershed/drainage basin.
• A rivers velocity, gradient, discharge and
  channel shape affect erosion.
• Rivers transport material in suspension, solution
  and bed load.
• The competence size and capacity amount of
  material carried by a stream/river is dependent
  upon the rivers discharge and velocity.
• Depositional features are formed when discharge
  or velocity slows, depositing the load in quieter
  waters.

18
River Valleys

• The continuous erosion caused by running water
  tends to form V-shaped valleys that grow longer
  and wider over time.

19
Canyon formation

• Canyons form when a river cuts into its bed
  rapidly or when rock materials on the sides of
  the valley are resistant to erosion.

20
Rapids and Waterfalls

• If the riverbed is steep enough it can cause
  white-water rapids or waterfalls.
• Rapids and waterfalls are temporary features
  because stream erosion is greatest at these
  points.

21
Floods and Floodplains

• River floods are naturally occurring events that
  sometimes threaten populations

22

• Flood
• When a stream or river overflows its bank
• Flash Flood
• Caused by single cloudbursts in the narrow valley
  of a developing stream

23
Features of a flood plain

• Meander When a river winds back and forth
  within its flood plain. Formed from increased
  erosion along river banks.
• Oxbow lakes Form when a meander is cut off from
  the main river, usually by flooding.
• Levee Elevated ridges along the banks of rivers
  formed from deposition of sediment.

24

• Meander

• Oxbow Lake

25
Final summary . . .

• Youthful rivers form steep sided canyons and
  V-shaped valleys by erosion.
• Floods occur when a river exceeds its banks and
  fills a flood plain.
• A flash flood occurs when an individual
  cloudburst releases heavy rains over the narrow
  valley of a young stream.
• Meanders, oxbow lakes and natural levees are all
  features of a floodplain.

26
The End!!