River Landscapes And Processes Flashcards
What is the path of a River called
The Course
What are the Characteristics of the Upper Course
Steep Gradient
Steep V-Shaped Valleys
Little Discharge
What are the Characteristics of the Middle Course
Medium Gradient
Gentle sloping Valleys
Medium Discharge
What are the Characteristics of the Lower Course
Gentle Gradient
Flat, Wide Channel
High Discharge
What are the two Cross Sectional Erosion Techniques
Vertical Erosion - where rocks erode the base of the river causing it to become deeper
Lateral Erosion - where the formation of meanders causes the river to become wider
What are different Weathering Processes for Rivers
Mechanical Weathering
Chemical Weathering
Biological Weathering
What is Mass Movement
This is where material slides down a valley due to gravity
What makes Mass Movement more likely to happen in Rivers
Undercutting of the Valley makes it weak
Weathering makes the material weak
Saturated Materials are heavier meaning they slide easier
What are the 4 Erosion Processes that affect Rivers
Hydraulic Action
Abrasion
Attrition
Solution
What are the 4 Transportation Methods that happen in Rivers
Saltation
Solution
Traction
Suspension
What is Deposition
This is where the River drops its material due to its energy loss.
This may happen because the River becomes shallow or the River can’t carry any more material.
How are Waterfalls made
This starts off with an area of hard rock followed by an area of soft rock.
The soft rock erodes first creating a step.
Over time the step becomes deeper due to erosion by Abrasion.
This creates a waterfall.
Over time, the hard rock becomes under cut and collapse causing erosion at the bottom of the river, which is called a Plunge Pool.
How are Meanders made
The outside of the bend has more energy meaning there is more erosion.
However, the inside of the bend has low energy leading to deposition and the formation of a point bar.
Over time erosion happens more and more to form a meander
How are Oxbow Lakes made
Over time meanders erode more and more until two bends meet. This bend is eroded but the water created a U shape connected to the river. Deposition causes a separate lake to close itself, which is called an Oxbow Lake.
What rare Flood Plains
They are areas beside the River that flood
How are Flood Plains made
When the River floods it loses its energy due to friction and deposits its material causing the land beside the River to become higher.
What are Levees
They are natural embankments beside the river.
How are Levees formed
When the River floods, the heavy material is deposited first causing the River side to become steeper and steeper.
How does Rainfall affect the erosion of Rivers
Rivers have a higher discharge when it rains meaning erosion is faster and more powerful.
The river will now also be able to transport more material due to the high energy levels.
Rainfall also increases Chemical Weathering.
How does Temperature affect the erosion of Rivers
In winter freeze-thaw weathering happens more.
In the summer, the high temperatures speed up the rate of Chemical Weathering.
What Short-Term weather events affect a Rivers Landscape
Storms - cause heavy rainfall meaning mass movement is more likely to happen.
Droughts - the water levels drop and dry ground also causes mass movements
How does Urbanisation affect a River
They make impermeable surfaces which increases surface run-off. This creates more energy in the river leading to faster erosion rates but also flooding
How does Agriculture affect rivers
Irrigation causes a reduction of water in rivers meaning erosion and transportation can’t take place.
How does Industry affect rivers
Causes air pollution which leads to acid rain and a higher Chemical Weathering rate.
What are the Physical Factors that increase the chances of Flooding
Prolonged Rainfall - is after a long period of rainfall that has caused the ground to not be able to absorb anymore water.
Geology - some rocks are permeable and some are permeable
Relief - rivers with steep valleys will receive water at a faster rate causing flooding.
What are the Human Factors that increase the chances of Flooding
Urbanisation - has caused the making of impermeable sound/tarmac
Deforestation - means there are fewer trees to intercept the water (less water interception)
What are the affects of Flooding
They can kill people
They can damage properties
They can contaminate freshwater sources
Crops can get ruined
What is Lag Time
This is when water doesn’t make it straight to the river because of interception etc.
What are Hard Engineering Strategies to stop Flooding
Dams and Reservoirs - store water caused by heavy rainfall, meaning there’s a smaller chance of suffering.
Channelisation - where the river is straightened so that it can store more water and decrease the chances of flooding.
What are Soft Engineering Strategies to stop Flooding
Floodplain Zoning - is where certain areas next to the river are restricted to build on
Washlands - where flooring takes place so that it doesn’t happen anywhere else.
