1_River Processes and Landforms

1_River Processes and Landforms

1. River Features

   • Source
     • The point where a river begins
   • Tributary
     • A small river or stream that joins up with a larger one
   • Confluence
     • The point at which a tributary joins the river
   • Mouth
     • The point where a river enters the sea
   • River Basin
     • An entire area drained by a river and its tributaries
   • Watershed
     • High ground that separates one river basin from another

2. Stages in a river's course

   • Youthful Stage(lower course)
     • The river has a steep gradient (slope)
     • The valley has a narrow floor and steep sides
   • Mature Stage(middle course)
     • The river has a gentler gradient
     • The valley has a wider floor and the sides are more gently sloping.
   • Old stage(upper course)
     • The river has an almost flat gradient
     • The valley has a wide, flat floor and gentle sides

3. River processes of Erosion

   • Hydraulic action
     • The force of the moving water that helps break up rock over time.
   • Abrasion
     • When the material(the load) carried along by the river hits its banks and bed, wearing them away.
   • Attrition
     • The rounding of pebbles, stones when they hit off each other and the river bed as they move downstream.

4. The river deposits its load when:

   • It loses speed and has less energy.
   • The river's volume decreases.
   • It enters a flat or gently sloping plain.
   • It flows into a lake or the sea.

5. River Transportation

   • Suspension
     • Particles are lifted and carried by the river water.
   • Saltation
     • Particles are bounced along the river bed.
   • Traction
     • Large stones are dragged or rolled along the river bed.
   • Solution
     • Some minerals, such as calcium carbonate (limestone), are dissolved in the water.

6. Features of the Youthful Stage

   • V-shaped valley
   • Interlocking spurs
   • Waterfalls
   • Gorge
   • Potholes

7. Features of the Mature Stage

   • Wider Valley
   • Meanders
   • Narrow flood plain

8. Features of the Old Stage

   • Oxbow lake
   • Levees
     • High banks along the river's channel. They form from river deposits
   • Delta
     • Form where some rivers enter the sea. They are often triangular in shape. They form from river deposits, which are deposited when the river slows down as it enters the sea
   • Large Meanders

9. People Interfere with rivers by building dams or man-made levees

10. Rivers interfere with people by flooding.

    • 1. Towns, villages and individual houses may be flooded when rivers overflow their banks
    • 2. Crops such as cereals and hay may be damaged on flood plains
    • 3. Floods may sweep away bridges, walls and people's homes

11. Advantages of river valleys to people

    • 1. Flood plains are used to grow some kinds of crops and rear animals for food
    • 2.Level land in valleys is used to build towns and cities
    • 3. Early settlers used riverside sites for water supply, food supply and transport facilities on the river.
    • 4. Norman settlers used rivers as a mode of defense around their castles
    • 5. Shallow places in rivers were used as crossing points. Most of our towns and cities developed at crossing points

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