Rivers Case Study Flashcards
Bangladesh Location
Between India and Burma. Asia
Bangladesh geography (rivers, possible natural hazards, etc.)
- Low lying delta
- 3 main rivers - Ganga, Bramhaputra and Meghna
- Prone to storm surges, earthquakes, cyclones
- Annual floods during monsoon
Reasons for living in floodplains
- Normal monsoon floods flood 25-30% of plains –> deposits silt, replenish soil moisture –> fertile
- Provide irrigation water for jute and rice
- Shrimp fisheries water
Physical flood causes
- Monsoon rains: Heavy rains cause rivers to burst banks. Soil erosion also caused –> makes flood worse bc siltation
- Cyclones: Common on the coats. May push storm surges onto land, causing floods.
- Melting glaciers: Glaciers melt more in spring, increasing river discharge rapidly
- Convergence of BGM: Three of these converge in Bangladesh –> higher discharge –> during monsoon two combined cause flooding
- Tectonic uplift of Himalayas: Water coming down has greater erosion potential –> carries sediment –> chokes rivers which floods
Human flood causes
- Deforestation in headwater areas: Increase in Nepal and Tibet pop., forest area cleared for fuel and grazing –> less evapotranspiration –> in Himalayas deforestation = lower interception rates and hence shorter lag time in peak discharge.
- Urbanisation of floodplains –> more impermeable surface, less vegetation = more runoff and greater floods
- Increasing pop. of Bangladesh: More people. Sinking of more wells –> water table lowers and subsidence.
- Climate Change: Glaciers melt more
Social impacts (positive)
- People rely on groundwater sources –> replenished
Social impacts (negative)
- Education disrupted
- Disease: 2004 flood in Dhaka 100,000 people suffered from diarrhoea bc contaminated water
- Damage to property: 2004 30 million people left w/o homes
- Loss of life: 2004 flood over 600 people killed
- Migration & displacement
Economic impacts (positive)
- Agricultural businesses flourish
- Fisheries do well –> floodwaters act like nurseries to young fish.
- People employed in these sectors –> fisheries employs 1.5 m fulltime employees
Economic impacts (negative)
- Victims lose land and livelihood
- Land is inundated –> 2007 2.2 million acres of cropland damaged
- Public buildings and services disrupted –> 2004, 7b dollars worth damage done to schools, and hospitals
- Govt. needs to spend for relief and aid
Environmental impacts
- Returns nutrients to the soil and fertility
- Fills in wetlands –> aquatic habitat connectivity increase
- More breeding, migration and dispersion of species triggered
Political impacts (positive)
- Frequent flooding allows govt. to study and mitigate severe effects
- Bangladesh provided shelter to victims of flooding in surrounding areas, hence areas may do the same for Bangladeshis
Political impacts (negative)
Rivers flow through India, China and Nepal. Any activity that may affect river flow and discharge there may cause tension. Eg:- India building dams increasing sedimentation
Flood action plan:
- Building embankments along the major rivers
- Plan to reduce flooding through sluice gates (controlled flooding), secondary embankments to hold excess water
- Successful - Prevented normal level floods along major rivers. Prevented flash flood along smaller eastern rivers. Protected land around some tidal rivers from saline flooding
- Unsuccessful: Doesn’t protect from higher moderate level storm surges. Doesn’t protect well from heavy annual floods from major rivers.
Flood warning system
Flood Forecast and Warning Centre - sends warnings up to 5 days early. Communicated to ministries via SMS, fax etc.
- Effective but should be more community based –> allowing vulnerable communities to receive warnings in their own language
Bridges
To keep villages accessible during floods.
Mini CS: Satiantoli is a village for which the community built a bridge to let residents access the highway. Lets 15000 people access. Boosted economy by allowing them to have a successful village market
