River processes

• What shapes the river and surrounding land in a drainage basin?

  Fluvial and landscape processes
• The landscape processes of weathering and mass movement shape the land surrounding the river
• Fluvial processes include erosion, transportation, and deposition.
• Types of weathering in order of example processes

  1️⃣ Physical weathering: Freeze-thaw

  2️⃣ Chemical weathering: Acidic rainwater

  3️⃣ Biological weathering: Plant roots
• Where does weathering occur?

  In-situ
• Physical weathering breaks rocks into smaller pieces due to changes in temperature.
• Chemical weathering occurs when rocks disintegrate and dissolve in slightly acidic rainwater
• What are two examples of physical weathering?

  Freeze-thaw and exfoliation
• How do plant roots contribute to biological weathering?

  They break rocks apart
• Mass movement involves large-scale movement of material.
• Match the type of mass movement with its description:

  Slumping ↔️ Undercutting by the river

  Soil creep ↔️ Gravity-driven slow movement
• When does slumping often occur in river valleys?

  Soft over hard material
• Soil creep is a slow, gravity-driven process that moves weathered material down a slope.
• In hot, wet climates, chemical and biological weathering are dominant
• How does heavy rainfall affect mass movement?

  Increases it
• What is the relationship between slope gradient and mass movement?

  Steeper gradient = more mass movement
• Freeze-thaw weathering is more common at higher altitudes due to low temperatures.
• Physical weathering is more common on a colder, north-facing slope due to the higher likelihood of freeze-thaw
• How does vegetation reduce mass movement?

  Roots bind the soil
• What percentage of a river's energy is used to overcome friction?

  95%
• There is more friction in the upper course of a river because it is shallow and narrow.
• What are the two uses of a river's energy after overcoming friction?

  Erosion and transportation
• The greater the discharge and velocity, the more energy a river has for erosion and transportation
• There are four erosion processes that change the shape of a river channel.
• What is hydraulic action in river erosion?

  Water force removes material
• Vertical erosion is dominant in the upper course of rivers.
• Where is lateral erosion dominant in a river?

  Middle and lower course
• Deposition occurs when a river does not have enough energy
• Processes of transportation in a river

  1️⃣ Traction: Larger rocks roll

  2️⃣ Saltation: Smaller material bounces

  3️⃣ Suspension: Lighter material is carried

  4️⃣ Solution: Materials are dissolved
• What are two causes of reduced energy in a river that lead to deposition?

  Reduced discharge and gradient
• The heaviest material carried by a river is deposited first and is known as bedload.
• Match the factor affecting fluvial processes with its effect:

  Climate ↔️ Heavy rainfall increases discharge

  Slope ↔️ Steep slopes increase erosion

  Geology ↔️ Softer rocks erode faster

  Altitude ↔️ Melting snow increases discharge
• How does a south-facing slope affect discharge?

  Decreases it
• What does the long profile of a river show?

  Changes in river gradient
• Most long profiles of rivers have a concave shape.
• The upper course of a river includes areas that are steep with uneven surfaces
• What is the gradient of a river in its lower course?

  Almost flat
• Match the river course with its characteristics:

  Upper course ↔️ Shallow and narrow channel

  Middle course ↔️ Wider and deeper channel

  Lower course ↔️ Flat floodplains and deposition
• In the lower course of a river, flat floodplains are a key feature
• What type of erosion is dominant in the upper course of a river?

  Vertical erosion