Rivers Flashcards
Describe the shape of a upper course long profile
Steep gradient On moutains/ higher ground Small river volume Slow river flow-rocks and boulders provide friction Near the source
Describe the long profile of the middle course
Gentle gradient
Increase in speed and volume of river
Begins the meander
Comes of hills onto floodplain
Describe long profile of lower course
Almost flat Greatest volume of water Fastest flow Flows out to sea Floodplain
Cross profile of the upper course
Small river-shallow Narrow channel V shape valley-deep and steep sided Turbulent from rocks Vertical erosion
Cross profile of the middle course
U shape valley-smaller and less steep Wider and deeper channel Increased speed Lateral erosion Tributaries= increased energy of river
Cross profile of lower course
Very flat and wide valley Fastest flow- lots of energy Lateral erosion Lots of deposition when meet the sea Floodplain Greatest volume of water- wide and deep channel
What is the hydro logical cycle
A closed system- water can’t be added or lost it just changes state
What is the definition of a river
A large natural stream where water is held before flowing out to sea
What are the different states of water in the hydro cycle
Water vapour (clouds) to rain to the river to the sea (+ice)
How does water move in the hydro cycle
Precipitation Evaporation Surface run off Infiltration- through the soil perculation - through ground rock
Why does deposition occur
The velocity of the river decrease so it has less energy to carry/transport its load
Larger rocks are deposited when river has a lot of energy for traction
Sediment is deposited further downstream
Lots of deposition at the mouth, where there is interaction between the tides and a gentle gradient
What rock does there need to be for a waterfall to form
Hard on top of soft
When does a gorge form
When the waterfall retreats leaving a steep sided gorge behind
What are leeves and what do they act as
Leeves are embankments that follows the course of the river, along the channel and is made from transported material, deposited in a flood. They build up in layers
They act as a natural flood defence by deepening the river channel
What is a meander
A naturally occurring bend in a river
Where does the water flow fastest in the river
On the outside of the bend= erosion
What 8 factors affect river discharge and flooding
Temperature Precipitation Previous weather Land use-urbanisation Rock type Relief Snow melt Deforestation
What is lag time
Delay between peak rainfall and peak discharge
More surface run off=shorter the lag time which means a greater river discharge so a greater chance of flooding
What were the factors affecting the boscastle flooding
No trees and lots of bare farmland Steep relief Bodmin moor because saturated quickly Storm became stuck over boscastle from east lily winds 8 inches of rain in 8 hours
What were the environmental impacts of boscastle flooding
Fuel from cars was spilt and went into the sea
Lots of debris taken into the sea= increased water pollution
River banks eroded and mult and silt everywhere
Trees uprooted
What were the human impacts of boscastle flooding
Financial impacts Long term stress and anxiety Tourism struggled and didn't recover until 2005 115 cars swept away No one died People were stuck in cars Buildings collapsed-25 businesses destroyed Car park ruined People trapped in buildings Bridge swept away
What were the responses to boscastle
Short term:
150 people airlifted to safety
Divers went in search of people in cars
Helicopters and firefighters arrived quickly
Money was given to help with rebuilding and to help for damage of homes (deputy prime minister and prince Charles)
Long term:
Afforestation in the drainage basin= better drainage and interception so longer lag time
River straightened and deepened= can hold more water, and flows to sea quicker
Main car park raised= cars won’t be swept away, provides space for excess water to go so reduces damage to buildings
What is there annual flooding in Bangladesh
3 main rivers join in Bangladesh and lots of other little rivers
Effected a lot by climate change= melting of snow in the Himalayas
Very flat relief, no more than 3m above sea level
Huge urbanisation so lots of concrete and deforestation
Monsoons and cyclones
What were the impacts of the 2012 flood
Crops were ruined, so no income and lots of starvation
Bridges collapsed so travel stopped
Mudslides so homes and people buried
Many died from drowning
250000 people displaced
15000 temporary homes set up
Very little clean water from mix with sewage
What were the responses to the Bangladesh flooding
Short term: Houses were rebuilt Animal feed donated Army helped but didn't have sophisticated equipment and tools People went looking for others Oxfam £74million donated by the UN Long term: Embankments built (from natural material) that control flood water and deepen river channel, and also raise villages or encircle them, so the homes are crops are protected Houses built on stilts Dams and gates built, to control water Animals and crops raised higher
