Erosion & Transportation
Hydraulic Action: Force of the water hitting the bed and the banks.
Abrasion: When the load the river is carryig repeatedly hits the river bed causing some of the material to break off.
Attrition: When the stones and boulders carried by the river knock against each other and over time are weakened, causing bits to fall off and reduce in size.
Solution: When the river flows on certain types of rock such as chalk and limestone - they're soluble in rainwater.
Traction: Largest material: too heavy to lose contact with the bed so it's rolled along.
Saltation: Small stones and frains of sand bouncing along the bed. Lighter load.
Suspension: Carrying fine material that floats in the river
Solution: Dissolved load (chalk and limestone)
Waterfalls and Gorges
Meanders and Oxbow Lakes
Levees and Floodplains
- Precipitation: Any moisture reaching the ground
- Interception: Water being prevented from reaching the surface by trees or grass
- Surface Storage: Water held on the ground surface
- Infiltration: Water sinking into soil/rock from the surface
- Soil Moisture: Water held in the soil layer
- Percolation: Water seeping deeper below the surface
- Groundwater: Water stored in the rock
- Transpiration: Water lost through pores in vegetation
- Evaporation: Water lost from ground/vegetation
- Surface Run-off: Water flowing on top of the ground
- Throughflow: Water flowing through the soil layer parallel to the surface
- Groundwater Flow: Water flowing through the rock layer
- Water Table: Current upper level of saturated rock/soil where no more water can be absorbed
2004 - July to September
- 40% of Dhaka was underwater
- 60% of the country submerged
- 600 deaths
- 30 million homeless
- 100,000 people had diarrhoea
As the year progressed
- 750 dead
- Dhaka airport flooded
- $7 billion schools and hospital damage
- Rice was washed away
Aftermath: Food supplies, medicines, clothing and blankets distributed. Transport system difficult. Local communities rebuilt their homes. Disease was a threat. UN appealed for $74 million, but had received only 20% by September. WaterAid helped too.
Involves the use of technology in order to try to control rivers.
Multi-purpose Project: The Three Gorges Dam, China
- Constructed at Yichang on the River Yangtse
- Benefit 15 million people in high-risk flood areas
- Protect 25,000 hectares of farmland
- Yangtse used to carry over 500 million tonnes of silt every year
- 50% of it is now deposited behind the dam
- 1.4 million people were forced to relocate
- $30 million of the funds set aside for the project has been taken by corrupt local officials
In this way the river is made to follow a new shorter, straight section and abandon its natural meandering course.
Soft Engineering // Water Supply
Floodplain Zoning: where the flood risk across different parts of the floodplain is assessed and resulting land use takes this into account.
How rivers in the UK manage to provide the water supply:
- Houses are being designed with better water efficiency
- Devices are fitted to toilet cisterns to reduce water use
- Rainwater can be collected
- Bath water can be recycled to flush toilets
- More people are taking showers than baths