AS Rivers

INPUTS: Precipitation

FLOWS: Through-flow, surface run-off, infiltration, percolation, groundwater flow and channel flow.

STORES: Interception, surface-storage, vegetation storage, soil water storage, groundwater storage and channel storage.

OUTPUTS: Transpiration, evaporation, river run-off. 

• Area
• Shape
• Slope
• Rock type
• Soil
• Land use
• Drainage density
• Precipitation/ Tempreature
• Tidal conditions
• Rainfall factors

Hydraulic Action: Turbulent flow lifts sediment out of the river banks leading to undercutting and eventual bank collapse. 

Abrasion (Corrasion): Sediment scouring or rubbing along bed or bank from fine particles to boulders, eroding it. 

Attrition: Reduction in particle size as they knock into each other becoming smaller and rounder further downstream. 

Corrosion: Rocks dissolve in the water e.g. carbonate rocks (limestone/ chalk.)

Traction: Boulders and rocks are rolled along the river bed.

Suspension: Fine particles are carried along by rive resulting in muddy colour of river. 

Saltation: Smaller pebbles and rocks "Bounce" along the river bed.

Solution: Minerals e.g. carbonates (chalk/ limestone)  are dissolved in the river.

Upper Reaches                                                   Lower Reaches                         

Low discharge                                                         High Discharge

Coarse Sediment load                                            Finer sediment load

Steep gradient                                                        Gentler gradient

Vertical erosion dominant                                      Lateral erosion dominant

Head ward erosion also occurs

Closed V-shaped valley                                        Open U-shaped valley

Meandering                                                         Braiding                                     

Less load                                                               Large load

Fine load                                                               Coarse load

Cohesive Banks                                                     Crumbling banks

Gentle slope                                                          Steep slope

Short term responses

• Resulting from 175mm of rain in 36hours.
• 3 dead.
• 125 Injured.
• Communication effected.
• 300 premises flooded

Long term Impacts

• Homes had to be rebuilt.
• Some people who were uninsured were left homeless.
• Business trade was lost.
• Emotional impacts upon people.

Costs

• Final bill was nearly £250 million.
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Causes of Bangladesh floods:

• Snow melting from the Himalayas..
• 80% of Bangladesh is a floodplain.
• Silt blocks river channels and make it difficult to discharge.
• Heavy monsoon rainfall.
• Trees have been cleared for rainfall.
• Two big rivers (Ganges and Brahmaputra) join in Bangladesh. 
• 70% of land is less than 1m above sea level so water can't drain away.
• Cyclones coming of the see and huge rains in monsoon seasons.