Bangladesh Flooding Causes Flashcards
Name of rainy season in Bangladesh
Monsoon
When did the monsoon rains begin
June 2004
3 main causes
Climatic, Terrestrial processes, Human activity
How are monsoon rains caused
In winter ITCZ moves south (leaves high pressure north of India). Dry winds blow out from land to sea.
June, July & August ITCZ moves north- low pressure brings summer monsoon winds which bring moist air off sea
What happened late June 2004
Heavy rain swelled Meghna which reached peak early July. Brahmaputra burst early July due to heavy rain in north –> flash floods in N and W central districts –> 38% was covered by water
What happened in September 2004
Monsoon hit again- worst in 50 years. 1 week average rain fall was 300mm daily (highest since 1952). This time Ganges caused most of flooding
Effect of Himalayan snow melt
Gangori Glacier feeds Ganges- retreats at average of 25 metres a year
Effect of cyclones
Bring storm surges and slow down rate at which river water flows into sea
What was the type of rainfall that was a key contributor
Relief rainfall from Himalayas
How much of country is a delta and floodplain
1/3 on Ganges delta and 80% is floodplain
Height above sea level
Most of country is 10 metres below sea level
Effect of global warming
Rising sea levels & melting glaciers –> water cannot go away quickly & more water being put into river
Effect of storing of water
Stored for irrigation upstream in reservoirs reduced amount of silt deposited so level of land not build up
Extraction of groundwater
Lowered water table & caused land to subside by approx 2.5m
Urbanisation & population growth
More urbanisation means higher peak flows with shorter lag time and greater peak discharge
Nepal (stage 2) increasing so pressure to provide food and fuel (deforestation) –> SRO, land slides, soil erosion –> river carrying capacity & channel flow decreases
