IGCSE Geography: Rivers

Water Cycle and Flows

• Water cycles between the atmosphere and Earth's surface.
• Main flows: evaporation, precipitation, and rivers.
• Examples of stores: seas, glaciers, and lakes.

River Drainage

• Precipitation reaches rivers via:
  • Direct flow from the atmosphere.
  • Surface flow.
  • Flow through permeable rocks and soil.
• A drainage basin (or catchment) is drained by a river and its tributaries.
• Watershed: boundaries separating different drainage basins.

River Erosion, Transportation, and Deposition

• Erosion Processes:
  • Corrosion: chemical weathering.
  • Corrosion: physical weathering.
  • Hydraulic action: water force causing erosion.
  • Attrition: rocks breaking into smaller pieces.
• Transportation Processes:
  • Solution: dissolved materials.
  • Suspension: fine sediments carried in water.
  • Saltation: hopping of particles.
  • Traction: rolling of large boulders.

River Profiles

• River's Long Profile:
  • Changes from source to mouth.
  • Downstream: decreased gradient, increased water volume, more sediment.
• Upper Course Landforms:
  • Erosion forms potholes, v-shaped valleys, interlocking spurs.
  • Waterfalls retreat upstream forming gorges.
• Middle Course Landforms:
  • Lateral erosion creates meanders and river cliffs.
  • Deposition forms slip-off slopes.
• Lower Course Landforms:
  • Features include flood plains, oxbow lakes, levees.
  • River enters the sea through estuaries or deltas.

Flooding and River Regime

• Flooding occurs when river discharge exceeds channel capacity.
• Flood Causes:
  • Increased precipitation or spring snowmelt.
  • Soil saturation leading to quick runoff.
  • Non-porous rocks reduce absorption.
• Human Impact:
  • Densely populated floodplains due to fertile soils.
  • Urban development increases runoff.
  • Deforestation increases runoff.

Flood Prevention and Management

• Flood prevention involves minimizing runoff and using reservoirs.
• Embankments and relief channels confine floodwater.
• Increasing flow rate by widening/deepening channels.

Human Activities and River Management

• Whole basin approach for effective river management.
• Dams/reservoirs for hydroelectricity, recreation, and leisure.
• Upper basins for farming, quarrying, and water storage.
• Estuaries suitable for industry due to import/export facilities.