S1 2nd Exam

• Monsoons


  Winds that change directions seasonally, formed by the differences in the heating of land and sea in China
• Formation of summer monsoons

  1. Long duration of insolation and high sunshine intensity in summer

  2. Land absorbs heat faster than sea

  3. Hot air rises, forming a low-pressure area

  4. Wind blows from high pressure area to low pressure area, forming southeast and southwest monsoons
• Formation of winter monsoons

  1. Short duration of insolation and low sunshine intensity in winter

  2. Land loses heat faster than sea

  3. Cold air sinks, forming a high-pressure area

  4. Wind blows from high pressure area to low pressure area, forming northeast monsoons
• Monsoon region


  • Eastern and southern parts of China
  • Receive a lot of rainfall from onshore summer monsoons
• Non-monsoon region


  • Northwestern part of China
  • Affected by summer monsoons, receives less rainfall and is drier
• Distance from the sea

  • Places closer to the sea receive more rainfall
  • Onshore winds and typhoons bring abundant rainfall to coastal regions
  • Wind loses moisture gradually as it moves inland, resulting in wetter climate in southeast and drier climate in northwest
• Relief


  • High mountains in western China block moist air from the ocean, forcing it to rise and bringing abundant rainfall to India
  • Air becomes dry when reaching northwestern China
• Regions in China based on annual rainfall

  • Humid region
  • Semi-humid region
  • Semi-arid region
  • Arid region
• Humid region


  Mainly in the south of Chang Jiang
• Arid region


  In the northwestern inland areas
• The distribution of water resources in China is determined by rainfall, which is mainly affected by monsoons and relief (Himalayas)
• Flooding

  1. River discharge increases suddenly

  2. Exceeds channel capacity

  3. River overflows banks
• Flooding


  Occurs when river discharge exceeds channel capacity and river overflows banks
• Flooding example

  • Bailong Jiang in Gansu
• Social impacts of flooding

  • Houses were damaged, people lost homes
  • Roads and bridges destroyed, affected areas less accessible, slow rescue work
  • Water resources were polluted, increased disease risk
  • Death and injury
• Economic impacts of flooding

  • Industrial and commercial activities stopped
  • Government had to spend more money on rescue and recovery
  • Farmlands drowned, crop failure, reduced food production
  • Loss of property
• The risk of flooding increases

  When there is a sudden increase in river discharge and a decrease in channel capacity
• Natural factors causing flooding

  • Heavy and prolonged rainfall
  • Snowmelt
  • Climate change
  • Low-lying relief
• Heavy and prolonged rainfall

  Monsoon winds and typhoons bring a lot of rain to eastern and southern China, increasing river discharge rapidly. Storm surges caused by typhoons also lead to widespread flooding in the coastal regions.
• Snowmelt

  In spring, the snow in the high mountains of western China melts. Large amounts of meltwater flow into the rivers, increasing river discharge as a result.
• Climate change

  Bringing more extreme rainfall events to China. The glaciers in the west are melting more quickly due to warmer temperatures.
• Low-lying relief

  • The lower courses of the major rivers in China are located in the east.
  • The flat and gentle relief of the region favours the deposition of sediments.
  • Riverbeds become shallower
• Human factors causing flooding


  • Deforestation
  • Reclamation of lakes
  • Impermeable urban surfaces
  • Poor maintenance of flood defences
• Deforestation

  People have cleared large areas of forests. As vegetation cover reduces, soil erosion intensifies.
• Reclamation of lakes

  Lakes can:

  1. reduce flood risk by storing water
  2. regulating river discharge.

  However, many lakes in China have been reclaimed for farming and urban development.
• Impermeable urban surfaces


  • Many ground surfaces have been paved with concrete.
  • They prevent the infiltration of water.
  • Surface runoff increases drastically during heavy rain.
• Poor maintenance of flood defences


  Flood defences such as dams and dykes are built to protect cities against flooding. However, some flood defences in China are poorly maintained. They are unable to hold the rainwater or may even collapse during rainstorms.
• Government measures to reduce flood risk

  1. Preventive measures

  2. Remedial measures
• Preventive measures


  • Engineering works
  • Land use planning
  • Flood warning system
• Engineering works


  1. Dams, reservoirs: regulate river discharge downstream and store rainwater

  2. Dykes: increase channel capacity and prevent rivers from overflowing

  3. River channels: straightened, widened, deepened to increase the speed of river flow and channel capacity

  4. Dredging: remove mud from riverbeds and maintain channel capacity
• Land use planning


  1. Increasing forest cover

  2. Protecting and restoring lakes

  3. Land use zoning
• Flood warning system


  • Government uses technology to monitor rainfall
  • Issuing early flood warnings depending on water level of river
• Remedial measures


  1. Immediate rescue

  2. Clean-up works
• Immediate rescue


  Rescue teams are sent to the impacted areas to save people. Emergency supplies including food and water are provided for the victims.
• Clean-up works

  After a flood, streets are cleaned and the floodwater is drained away. Damaged infrastructure need repair as well such as:

  1. railways
  2. bridges
  3. electricity pole