Water%20Erosion:

1

• Water Erosion
• How do processes involving water change Earths
  surface?
• Part 1

2

• What is the MAJOR agent of erosion that has
  shaped Earths land surface?
• moving water

3

• Water moving over lands surface is called
• runoff.
• Runoff may cause
• sheet erosion.

4

• The amount of
• water runoff in an area depends on
• 5 main factors

5
Factors that affect Runoff

• The amount of rain an area receives.
• More rain more runoff
• Vegetation - grasses, shrubs trees reduce
  runoff.
• More vegetationless runoff
• Type of soil - some soils absorb more water than
  others
• Shape of the land steep slopes have more
  run-off, which causes more erosion
• How people use the land parking lots crop
  removal increase run-off.

6

• Runoff overtime
• How does runoff over time affect the land and
  water?

7
Rills Gullies

• As runoff travels across the soil, rills form.
• Rills are tiny grooves in the soil that grow
  larger forming gullies.
• A gully is a large groove or channel in the soil
  that carries runoff after a storm. It moves soil
  rocks.
• Gullies only contain water after it rains.

8
Streams Rivers

• Gullies join together to form a larger channel
  called a stream.
• Water continuously flows here and rarely dries
  up.
• Small streams may be called creeks or brooks.
• Small streams flow together to form a large
  stream called a river.

9
Rill, Gully, Stream
Rill erosion at a construction site. Image by M.
Mamo, Labels added by UNL
Stream
Gully erosion in a pasture. Image by NRCS
10
Tributaries

• Streams grow together by getting water from
  tributaries.
• A tributary is a stream or river that flows into
  a larger river.
• Tributaries collect their water from the
  drainage basin or watershed.
• An example The Missouri Ohio rivers are
  tributaries of the Mississippi river.

11
Rivers Tributaries
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• Rivers
• cause erosion and create valleys,
  waterfalls, flood plains, meanders and oxbow
  lakes.
• form on steep mountain slopes.

13

• How do they flow?
• Quickly and follow a narrow path
• How do they erode?
• Rapidly
• The result is that rivers form deep, V-shaped
  valleys.

14
Valleys
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15
Features of rivers What features are formed
by erosion along a river?
16
Waterfalls

• Occur where?
• Where a river meets an area of hard slowly
  eroding rock
•  Then flows over softer rock downstream.
•  How does softer rock erode?
• The softer rock erodes away faster.
• What results from this erosion?
• A waterfall develops.

17
Waterfalls
Waterfalls at the Plitvicka Jezera National Park
in Croatia
Minnehaha Falls, Minneapolis Minnesota
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18
Flood Plain

• What is a flood plain?
• A wide valley in which a river flows
• What happens to the land during a flood?
• The water in the river over flows its banks into
  this wide river valley area.

19
Flood Plain
20
Meanders

• What are meanders?
• Loop-like bends in the course of a river.
• Where how do they occur?
• They occur as the outer bank of a river is
  eroded deposits are dropped on the inner bank
  of the bend in a river.

21

• Example
• The southern stretch of the Mississippi River
  meanders on a wide, gently sloping flood plain
  area.

22
Mississippi River Meanders
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23
Oxbow Lakes

• What is an oxbow lake?
• A meander that has been cut-off from the river.
• They may form when a river floods as high water
  finds a straighter path downstream . As flood
  waters fall, sediments dam up the ends of the
  meander and a lake forms.

24
Oxbow Lakes
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