River Landscapes Flashcards
(45 cards)
What do long and cross profiles of a river show?
Changes in river characteristics from the source to the mouth.
Long profiles illustrate the gradient, while cross profiles provide cross-sections of the river channel.
What is the typical shape of a river’s long profile?
Concave shape.
This shape reflects the changes in gradient from the source to the mouth.
What are the characteristics of the upper course of a river?
- Steep gradient
- Uneven surfaces
- Vertical erosion
- Narrow channel
- Low velocity
- Large bedload
- Rough channel bed
- High levels of friction
The upper course is characterized by significant vertical erosion.
What are the characteristics of the middle course of a river?
- Gentle valley sides
- Wider channel than upper course
- Greater velocity than upper course
- Material decreases in size
- Smoother channel bed
- Lower friction
- Lateral erosion
The middle course sees a transition from vertical to lateral erosion.
What are the characteristics of the lower course of a river?
- Flat floodplains
- Wider than middle course channel
- Greater velocity than middle course
- Material mainly sediment and alluvium
- Smooth channel bed
- Lowest friction
- Dominant deposition
In the lower course, deposition becomes the dominant process.
What are the four processes of erosion that change the shape of the river channel?
- Hydraulic action
- Abrasion
- Attrition
- Corrosion (solution)
These processes work together to shape the river’s channel.
What is vertical erosion and where is it dominant?
Erosion that increases depth of the river and valley; dominant in the upper course.
This type of erosion occurs as the river cuts down into its bed.
What is lateral erosion and where is it dominant?
Erosion that increases the width of the river and valley; dominant in the middle and lower courses.
Lateral erosion occurs as the river erodes sideways.
What causes deposition in a river?
- Reduced discharge
- Decreased gradient
- Slower flow on the inside of bends
- River entering a sea/ocean or lake
When the river loses energy, it drops its load.
What are the main landforms found in upland river areas?
- Waterfalls
- Gorges
- V-shaped valleys
- Interlocking spurs
These landforms are a result of vertical erosion and other processes.
How are waterfalls formed?
Where there is a drop in the river bed due to changes in rock hardness.
Soft rock erodes quicker, leading to undercutting of hard rock.
What are the characteristics of V-shaped valleys?
Formed by vertical erosion; steep sides and narrow bottom.
Weathering and mass movement contribute to their steep sides.
What are meanders and how do they change over time?
Curves in the river formed by lateral erosion; change shape and position due to erosion and deposition.
Fastest flow is on the outside leading to erosion, while slower flow on the inside leads to deposition.
What is an oxbow lake?
A lake formed when a meander is cut off from the main river channel.
This occurs during flooding when the river cuts through the neck of the meander.
What are floodplains?
Flat expanses of land on either side of a river formed by the migration of meanders.
They are created as the river overflows its banks during high discharge.
What are levees?
Natural embankments formed by the deposition of heaviest materials closest to the river channel.
They help to contain the river within its banks during floods.
What factors increase the risk of flooding?
- Steep slopes
- Impermeable rock types
- Saturated or frozen soil
- Heavy rainfall
- High drainage density
- Lack of vegetation
These factors lead to increased overland flow and reduced infiltration.
What is a flood hydrograph?
A graph showing changes in river discharge after a rainfall event over a short period, usually 24 hours.
It includes features like peak discharge and lag time.
What human activities can affect storm hydrographs?
- Deforestation
- Afforestation
- River management
- Urbanisation
- Agriculture
- Climate change
These activities can alter discharge levels and lag times.
What is the impact of urbanisation on storm hydrographs?
Increases rates of overland flow, reducing lag time and increasing discharge.
Impermeable surfaces prevent water infiltration.
What is the population of York?
Just over 200,000
List years when serious flooding occurred in York.
- 1947
- 1978
- 1991
- 1995
- 2000
- 2015
What was significant about the floods in 2000?
They were the worst on record
How much did the River Ouse rise during the 2000 floods?
Almost 5.4 meters above its normal level
