#geog1

Ecosystems: a natural unit in which life cycles of plants, animals and other organisms are linked to each other and to the non-living components of the environment to form a natural system.

Biotic elements: this is the living environment which is made up of animals, plants, fungi etc. 

Abiotic elements: these are the non-living components, includes light intensity, moisture, soil pH, soil nutrient content etc. 

Community: these are all the different species within an ecosystem.

Population: the number of individual species within an ecosystem i.e. a particular species. 

Physical Facts:

The capital city is Dhaka

The Himalayas are situated to the North of the country.

It is situated on an Arcuate Delta - very fertile lands.

80% of land is less than 1 metre above sea level.

In Summer 25% of land is submerged under sea and it can reach as high as 40%.

The river is rapidly changing as 1820 million tonnes of sediment being carried through Bangladesh.

Nation with a high drainage density.

Human Facts:

It's an LEDC with an average income of $360, many are surviving on a dollar a day.

Population of 147 million, population density is high at 1019 people per km. 

48% suffer from malnutrition and only 0.2% have computer access, 0.4% have a telephone and only 14% are literate.

Evaluation of Bangladesh flooding: 

+ Flooding is essential as farming season is planned around the floods and rice requires large amounts of water (their main crop).

+ Leaves behind fertile silt - one of the most fertile countries in the world. In normal years the floods cover 1/3 of the land in shallow water.

+ June-September monsoon season replenishes underground water supplies, provides soils with nutrients and provides a breeding ground for fish (source of animal protein). 

- Death through drowning, snakebites, electrocution from floating power cables and waterborne diseases e.g. cholera, diorrehea etc.

- Families torn apart - orphans 

- Food and water shortages as the crops have been ruined and the water supply polluted. 

- Destruction of communications leaving it almost impossible to deliver aid. 

- Much soil erosion due to the silting up of the river channel reducing its capacity.

Case studies

May 1995: 40,000 dead, resulted in famine.

September 1988: 2,400 dead, 25 million left homeless, 80% of the country under at least 1m of water, infrastructure ruined and they experienced the heaviest monsoon rains ever.

June 2004: $7 billion worth of damage, 1 in 3 workers off sick with waterborne diseases. 600 dead, 30 million left homeless, 20 million in need of food and 100,000 suffered from diorrehea 

Management of Flooding in Bangladesh

Leveés:

 + Stops smaller floods by increasing the river's capacity.

 - They can burst increasing the damage caused. They may trap water - becomes stale carrying waterborne diseases.

Storm Shelters: 

+ gets people away from the flood danger areas, reducing the death toll e.g. 1991- 150,000 died - 1998 only 1000 died.

 - Not enough flood shelters and they've poor access.

Early warning systems:

+ This will allow people to evacuate safely and reach storm shelters.

- Not many people have access to communications (TV, phones, internet) so few will know about the flood risk.

Afforestation:

+ It will decrease lag time, increase interception, less surface run-off and less soil erosion - it's a long-term, sustainable solution.

- This is more long-term as tress take years to grow.

Dams:

+ allows flow to be controlled during flood periods and the stored water can be used during the dry season.

They are strongly linked to the process of deposition. They're composed of fine sediment which is dropped when the river loses competence as it enters an area of slow moving water.

Bird's foot delta

It has many distributaries which extend bounded (surrounded) by sediment that reach out into the sea. It's the shape of a bird's foot and an example is the Mississippi drainage basin.

Arcuate Delta 

They have a circular, convex shape with tributaries reaching out into the sea. It produces fertile, agricultural land. An example is the Nile drainage basin.

As fresh water and salty water meet it leads to an electrical charge being created which causes sediment to join becoming heavier --> deposition (flocculation). 

A natural levee forms when a river overflows its banks, the increase in friction caused by the contact with the floodplain results in increased deposition. 

A leveé is being constantly replenished/ restored. 

A hazard of leveés is that after a period of flooding the leveés prevent the water from entering back into the river. This causes disruption and damage to property. Leveés are prone to erosion and the leveé banks may collapse into the river causing its capacity which may result in flooding.

River needs energy to erode and transport materials and if it loses this energy deposition will occur. The heavier material will be deposited first while the lighter material will generally still be held in suspension e.g. silt. 

Hjustrom Curve

1. The larger the particle the more energy needed to erode or transport it.