Detailed Specific Example: Ganges/Brahmaputra

Causes of flooding in Bangladesh

Causes of flooding in Bangladesh

• The Ganges is 2,510 km long

  • It flows through India and Bangladesh, where it becomes the River Padma and joins with the Brahmaputra River

  • The drainage basin covers 1.2 million km²

  • The population living within the area drained by the Ganges is over 650 million people

• The Brahmaputra River is 3,969 km long

  1. It flows through Tibet, India and Bangladesh, where it joins with the River Padma

  2. The drainage basin covers 651,334 km²

• Both rivers;

  • Have their source in the Himalayan Mountains

  • Waters enter the sea in the Bay of Bengal

Human causes of flooding

• Deforestation, particularly in the upland areas

  • This leads to less interception and infiltration, increasing overland flow

• Human-induced climate change has led to increased melting of Himalayan snow and ice, which increases discharge

  • It may also have affected climate patterns, leading to increased frequency and severity of tropical cyclones

• Urbanisation, as the population increases and there is more rural-urban migration, leads to increased overland flow due to impermeable surfaces

• Agriculture increases overland flow and soil erosion, which reduces the capacity of the rivers

Natural causes of flooding

• Low-lying land in the Ganges delta in Bangladesh which is at or just above sea level, meaning that it floods more easily

• Monsoon climate, which means that there are heavy and prolonged rains for some months

• Tropical cyclones bring heavy rainfall

• Melting snow and ice from the Himalayas in spring leads to a rapid increase in river discharge

Impacts of flooding in Bangladesh

Impacts of flooding in Bangladesh

• The Ganges/Brahmaputra drainage basin regularly experiences floods, including most recently in May -July 2024 impacting approximately 40% of the population

• In July 2019, approximately one third of the country was underwater

  • More than 360,000 homes were destroyed

  • Approximately 5 million people were directly affected

  • Landslides damaged roads and infrastructure

  • Waterborne diseases such as malaria increased

  • Cox's Bazaar was severely affected displacing over 6,000 refugees

• 'Normal' floods are vital to provide fertile soil and irrigation, but increasingly flooding is becoming more unpredictable and extensive

Strategies to manage flooding in Bangladesh

Strategies to manage flooding in Bangladesh

• Bangladesh is a Low Income Country (LIC) 

  • The country lacks the money for large schemes to reduce the impact of flooding

• The World Bank and several high-income countries (HICs) funded the Flood Action Plan (FAP). The proposal included the following measures:

  • monitoring of flood levels 

  • construction of levées/embankments

  • building 5000 flood shelters

  • creating floodwater storage systems

  • a more effective flood warning system

  • building of dams to store water

  • reducing deforestation

• The FAP was not seen as a success because

  • Many parts of the project were never completed, including the dams and floodwater storage areas, due to inadequate funding and corruption

  • There was later a recognition that some flooding was necessary to maintain agriculture in many areas

  • Over 8 million people were forced to move to accommodate the FAP construction

  • Changing the channel upstream meant that areas downstream suffered more

  • The government cannot afford the maintenance costs

• New management suggestions include:

  • Better flood forecasting and warning systems

  • More well-stocked flood shelters

• These are less damaging to the environment and cheaper to maintain than hard engineering such as embankments, dams and floodwater storage areas