Rivers Flashcards
What is the rivers source
Where t.ye river begins
What is a drainage basin
The area from which water drains into the river
What is a water shed
And imaginary line that separates two drainage basins
What is a confluence
The point where two rivers join together
What is a tributary
A small river that joins the main river
What is the flood plain
Land that floods when a river overflows
What is the mouth of a river
Where the river flows into a sea or lake
What is the river bed
The bottom of a river channel
What is a river bank
The side of a river channel
What is the channel
Where the river flows into
What us a river channel
Where the river flows
What is the rivers long profile
It shows how a rivers gradient changes as it flows from the source to the mouth
Describe the upper course of a river
Steepest part of the river which is usually small and very fast and downward erosion is the dominant process
Describe the middle course of a river
Starts to flow slowly and can look muddy due to lots of sediment being carried and it starts to get wider
Describe the lower course of a river
Has a large flood plain and the v shape valley has disappeared due to the river being really wide
What is erosion in a river
The gradual removal of rock from a rivers bed or banks
What are the 4 types of erosion
Abrasion, attrition, solution, hydraulic action
What is abrasion
When the bed and banks of a river are worn down by the rivers load.
What is attrition
The load being carried in the river bumping into each other which causes the particles becoming smaller
What is solution
The chemical of the rivers whiter. The acids slowly dissolve the bed and banks
What is hydraulic action
The force of the water wearing away the bed and banks
How does the gradient of a river affect the rate of erosion
A steeper grading means the water is pulled by gravity quicker which cuts down and erodes the channel
How does rock resistance affect the rate of erosion
The more erodible rock there is the quicker erosion occurs
How does the velocity of the water affect the rate of erosion
The quicker the water moves the faster erosion takes place
How does discharge affect the rate of erosion
The more water in a river means there is more power to erode which increases the rate of erosion
How does a v-shape valley occur
The river erodes downward, weathering loosens the solid rock around the sides, the loosened material falls down. This results in a steep sided valley which looks like the letter v
What is the bed load
This is the material carried by a river as it moves
What are the 4 transportation processes
Solution, suspension, saltation, traction
What is traction
large boulders and rocks that are rolled along the rivers bed
What is saltation
Small pebbles and stones that are bounces along the river bed
What is suspension
Fine material that is carried in the water
What is solution
Minerals that are dissolved in the water and are carried long through the water
What is a waterfall
A geological formation where flowing water drops into elevation as it flows over a cliff
How is a waterfall formed
Water flows over different types of rock. The soft rock wears away faster than the hard rock which causes a step to develop over time which the river plunges into as a waterfall. This cuts away at the rock behind the waterfall which causes the waterfall to move back leaving a gorge as it goes
What is the thalweg of the river
The line of fastest flow
What is a meander
The bends in a river
Where are meanders most commonly found
The middle course of a river
How is a meander formed
The Thalweg eroding the banks causing inner and outer bends and deposits the sediment of the sides of the river
What is an oxbow lake
A horse shoe/ semicircular area that represents the former course of a river
How is a oxbow lake formed
A meander getting bigger and the neck becoming gradually narrow which then gets cut off which causes the waterfall to take the easiest rout which eventually leads to the bend being fully isolated from the river
What is an estuary
The tidal part of a river where the fresh water from the river merges with the salt water from the sea
What is a levee
The deposited material found at the banks of a river
What causes flooding
Rain begins to fill the river channel and precipitation saturated the ground. The saturated ground causes the river to overflow and flow into the flood plain
What are some human reasons for flooding
Urbanisation, farming/ agriculture, deforestation
What are some physical reasons for flooding
V-shape valleys, impermeable rock, snow, rainfall
What is impermeable rock
Rock that can’t soak up any water
What is base flow
Starting and finishing flow of the river either die of increased discharge
What is peak discharge
Maximum discharge following rainfall
What is peak rainfall
Highest rate of precipitation during rainfall
What is lag time
The time between peak rainfall and peak discharge
What is a rising limb
Increasing discharge as storm water enters the river channel
What is a receding limb
Fall in discharge back to the base level
What are 4 ways of flood management
Dams, channelisation,retention ponds, afforestation
What are retention ponds
A pond that aloes runoff to be temporarily stored
What is channelisation
It reduces the friction between the water and banks which allows the water to move away from an area quicker
What is afforestation
The growth of trees which causes the flow of water towards the river channel
What are dams
They hold back water allowing it to be released in a controlled manner
What is hard engineering
Expensive structured that have an impact of the environment/ working against nature
What is soft engineering
An ecologically sensitive structure that works with nature and tends to be cheaper
What is discharge
The amount of water flowing through a river
