River Landscapes Flashcards
What is the path of a river as it flows downhill called?
Its course
What are the three courses of a river?
- Upper course
- Middle course
- Lower course
What does the long profile of a river show?
How the gradient changes
What do rivers form as they flow downhill?
Channels and valleys
What processes do rivers use to shape the landscape?
- Erosion
- Transportation
- Deposition
What determines the shape of the valley and channel along a river?
Whether erosion or deposition is the dominant process
What does the cross profile of a river show?
What a cross-section of the river looks like
Describe the valley and channel shape in the upper course of a river.
- V-shaped valley
- Steep sides
- Narrow, shallow channel
What characterizes the middle course of a river?
- Gently sloping valley sides
- Wider, deeper channel
What is the valley and channel shape like in the lower course of a river?
- Very wide, almost flat valley
- Very wide, deep channel
What are the two types of erosion that affect a river?
- Vertical erosion
- Lateral erosion
What is the effect of vertical erosion on a river valley?
It deepens the river valley and channel, making it V-shaped
Where is vertical erosion dominant in a river?
In the upper course of the river
What causes intense downwards erosion in a river?
High turbulence causing rough, angular particles to be scraped along the river bed
What does lateral erosion do to a river valley?
It widens the river valley and channel
In which courses of the river is lateral erosion dominant?
In the middle and lower courses
Fill in the blank: The upper course of a river typically has a _______ gradient.
Steep
True or False: The lower course of a river has a narrow and shallow channel.
False
Fill in the blank: The shape of the valley in the lower course of a river is _______.
Very wide and almost flat
What is hydraulic action?
The force of the river water colliding with rocks, breaking rock particles away from the river channel.
Hydraulic action is one of the four processes of erosion.
What is abrasion in the context of river erosion?
Eroded rocks picked up by the river scrape and rub against the channel, wearing it away.
Most erosion happens by abrasion and it is dominant in the upper course.
Define attrition as a process of erosion.
Eroded rocks crash into each other, breaking into smaller fragments and rounding off their edges.
Attrition causes particle size to decrease from a river’s source to its mouth.
What is the solution process in river erosion?
River water dissolves some types of rock, such as chalk and limestone.
This process occurs alongside other erosion methods.
How does the flow rate of a river affect erosion?
The faster a river’s flowing, the more erosion happens.
What is transportation in the context of rivers?
The movement of eroded material.
How material is transported depends on the velocity of the water and the size of the particles.
Fill in the blank: Large particles like boulders are transported by ______.
Traction
Fill in the blank: Pebble-sized particles are transported by ______.
Saltation
What are small particles like silt and clay transported by in a river?
Suspension
What happens during the solution process in river transportation?
Soluble materials, like limestone, dissolve in the water and are carried along.
What is deposition in the context of rivers?
When a river drops the material it’s transporting.
Deposition occurs when a river loses velocity and energy.
List reasons why rivers slow down and deposit material.
- The volume of water falls
- The amount of eroded material increases
- The water is shallower
- The river reaches its mouth
In which course of a river is deposition dominant?
Lower course
How does particle size affect deposition in a river?
Smaller particles are transported further and deposited closer to the river’s mouth.
Where do waterfalls typically form?
Where a river flows over an area of hard rock followed by an area of softer rock.
What process leads to the formation of a ‘step’ in a river?
Erosion of softer rock by hydraulic action and abrasion.
What happens as water flows over the step in a river?
It erodes more hard rock and more of the softer rock.
What is created when a steep drop is formed in a river?
A waterfall.
Give an example of a waterfall.
High Force waterfall on the River Tees, County Durham.
What happens to hard rock due to erosion at a waterfall?
It is eventually undercut and becomes unsupported, leading to collapse.
What is created at the foot of a waterfall as rocks collapse?
A deep plunge pool.
What happens over time due to more undercutting at a waterfall?
The waterfall retreats, leaving behind a steep-sided gorge.
What is the term for landforms created by rivers?
Fluvial landforms.
What type of valleys are created by vertical erosion in the upper course of a river?
Steep-sided, V-shaped valleys.
Why do rivers in the upper course wind around hillsides?
They lack the power to erode laterally (sideways).
What are the hillsides that interlock as a river winds around them called?
Interlocking spurs.
Interlocking spurs resemble which common item when viewed from above?
A zip.
Fill in the blank: The process where water erodes softer rock more than hard rock is known as _______.
Hydraulic action and abrasion.
True or False: Interlocking spurs are related to cowboys.
False.
What is the primary erosion type in the upper course of a river?
Vertical erosion.
What is created by the swirling rocks at the foot of a waterfall?
A plunge pool.
What are meanders?
Large bends in rivers formed in the middle and lower courses where there are both shallow and deep sections.
What is the thalweg?
The line of deepest water and fastest flow in a river channel.
What happens to the current on the outside of a bend?
The current is faster due to a deeper channel with less friction.
What forms on the outside of a bend due to erosion?
River cliffs.
What occurs on the inside of a bend?
The current is slower due to a shallower channel, leading to deposition.
What are slip-off slopes?
Deposited eroded material on the inside of a bend.
What processes cause erosion on the outside bend?
- Abrasion
- Hydraulic action
What eventually happens to meanders over time?
They can turn into ox-bow lakes.
What causes the outside bends of a meander to get closer?
Erosion.
What is the ‘neck’ in the context of meanders?
The small bit of land left between the bends before the river cuts through.
How does an ox-bow lake form?
Deposition cuts off the meander, and the river flows along the shortest course.
Fill in the blank: The river breaks through the land usually during a _______.
[flood]
True or False: The River Calder has formed several ox-bow lakes near Castleford, West Yorkshire.
True
What is a flood plain?
The flood plain is the wide valley floor on either side of a river which occasionally floods.
Flood plains are essential for the ecosystem and agriculture due to their nutrient-rich soil.
What happens to water when rivers flood?
When rivers flood, the water slows down, loses energy and deposits the material that it’s transporting, building up the flood plain.
This process is critical for maintaining the fertility of flood plains.
How do meanders affect flood plains?
Meanders widen as they migrate laterally across floodplains and also migrate downstream over time.
This migration contributes to the shape and size of flood plains.
What is a levee?
Levees are natural embankments (raised banks) along the edges of a river channel.
Levees help to manage flooding by containing river water within its channel.
What occurs during a flood regarding levees?
During a flood, eroded material is deposited over the whole flood plain, with the heaviest material deposited closest to the river channel.
This process helps to build up the levees over time.
Where are levees typically found?
Levees are typically found along the edges of river channels, such as the River Trent in Nottinghamshire.
Repeated flooding leads to the formation of levees.
What are estuaries?
Estuaries are tidal areas where the river meets the sea, found at river mouths.
Estuaries are important for wildlife and serve as nurseries for fish.
What is the significance of tides in estuaries?
The water in estuaries is tidal, meaning the river level rises and falls each day.
This tidal action influences sediment deposition and the ecosystem.
What happens to sediment during high tide in estuaries?
As the tide reaches its highest point, the water moves slowly and deposits sediment onto the valley floor.
This sediment buildup contributes to the formation of mudflats.
What are mudflats?
Mudflats are formed over time as more mud builds up in estuaries, such as the Severn Estuary in Gloucestershire.
Mudflats provide critical habitats for various bird species.
What is the land elevation like in estuary regions?
The land in estuary regions is close to sea level and the river valley is at its widest.
This geographical feature makes estuaries vulnerable to flooding.
What do contour lines indicate on maps?
Contour lines indicate the height of the land and the steepness of the slope.
The height is represented by numbers, while the steepness is determined by the closeness of the lines.
How does a river flow in relation to contour lines?
A river flows from higher contour lines to lower ones.
This is due to the force of gravity.
What shape do contour lines form where they cross a river?
A V-shape that points uphill.
This indicates the direction from which the river came.
What evidence from maps indicates the presence of waterfalls in the upper course?
Cliff symbols, close contour lines, and high nearby land.
The waterfall is marked, and the steepness is shown by the contour lines.
What does it mean if a river crosses many contour lines in a short distance?
The river is steep.
This indicates the upper course of the river.
What are the characteristics of a river in its lower course?
- Nearby land is low (less than 15 m)
- River does not cross contour lines
- River meanders across a flat area
- River is wide
- Large meanders and potential ox-bow lakes
These features indicate a floodplain.
Fill in the blank: A river’s narrowness is indicated by a _______.
thin blue line.
True or False: Contour lines that are very close together indicate a gentle slope.
False.
Close contour lines indicate a steep slope.
What does it indicate if contour lines are far apart on a map?
The slope is gentle.
This is typical in the lower course of a river.
What is a floodplain?
A large flat area where a river meanders.
It is typically found in the lower course of a river.
What are the symbols used to mark cliffs on maps?
Black, blocky lines.
In the context of river landforms, what does a steep-sided, V-shaped valley indicate?
The presence of a river in its upper course.
This is characterized by close contour lines and a narrow valley floor.
What is River Discharge?
The volume of water flowing in a river per second, measured in cumecs (cubic metres per second)
Discharge is key in understanding river flow dynamics.
What do hydrographs show?
How the discharge at a certain point in a river changes over time in relation to rainfall
Hydrographs are essential for flood risk assessment.
Define Peak discharge.
The highest discharge in the period of time you’re looking at
Important for assessing flood levels.
What is Lag time?
The delay between peak rainfall and peak discharge
Influences flood timing and risk.
What is the Rising limb of a hydrograph?
The increase in river discharge as rainwater flows into the river
Indicates how quickly a river responds to rainfall.
What is the Falling limb of a hydrograph?
The decrease in river discharge as the river returns to its normal level
Reflects the recovery phase after flooding.
What causes Lag time?
Most rainwater flows quickly overland (surface runoff) or soaks into the ground (infiltration) and then flows slowly underground to the channel
Understanding lag time is crucial for flood management.
What is flooding?
When a river’s level rises so much that it spills over its banks
Flooding poses significant risks to communities.
Name a factor that shortens lag time.
Heavy Rainfall
This increases surface runoff and discharge.
How does geology affect flood risk?
Clay soils and some rocks, like granite and shale, are impermeable, increasing runoff
Soil type is a critical factor in flood dynamics.
What effect does prolonged rainfall have on soil?
It can saturate the soil, preventing further rainfall from infiltrating and increasing runoff
This can lead to higher flood risks.
How does relief (land height changes) influence discharge?
In steep-sided valleys, water reaches the river channel quicker, rapidly increasing discharge
Topography plays a vital role in flood behavior.
How does land use impact flood risk?
Buildings made from impermeable materials and roads increase surface runoff
Urbanization significantly alters natural water flow.
What role do trees play in flood management?
Trees intercept rainwater, store water from the ground, and reduce runoff
Deforestation can exacerbate flood conditions.
Fill in the blank: _______ means that water arrives too quickly to infiltrate, increasing surface runoff.
Heavy Rainfall
This is a critical factor in flood events.
What are the two types of strategies to deal with flooding?
Hard engineering and soft engineering
What is hard engineering?
Man-made structures built to control the flow of rivers and reduce flooding
What is soft engineering?
Schemes set up using knowledge of a river and its processes to reduce the effects of flooding
Name a hard engineering method used to control flooding.
Dams and reservoirs
What is the purpose of a dam?
To act as a barrier across rivers and form a reservoir behind it
What are the benefits of reservoirs?
- Store water after heavy rain
- Control water flow
- Prevent floods downstream
- Generate hydroelectric power (HEP)
What is channel straightening?
Removing meanders by building straighter, artificial channels
What are embankments?
Raised walls built along river banks to prevent flooding
What is the purpose of flood relief channels?
To divert water around built-up areas or excess water when river levels are high
What role do flood warnings play?
They inform people about impending floods through various media
What is flood plain zoning?
Restrictions preventing building on parts of a flood plain likely to be affected by floods
What is one benefit of planting trees in the river valley?
Increases interception of rainwater and lag time
What is river restoration?
Making the river more natural by removing man-made levees
What are some disadvantages of dams?
- Very expensive to build
- Can flood existing settlements
- Material deposition in reservoirs can reduce farmland fertility downstream
True or False: Flood warnings can prevent floods.
False
What are some disadvantages of modifying buildings for flood preparation?
- Expensive
- Doesn’t guarantee safety from floods
- May give a false sense of security
What is a disadvantage of flood relief channels?
Increased discharge where the relief channel rejoins the river could cause flooding
Fill in the blank: Flooding may happen downstream due to _______.
[hard engineering methods]
What is a potential consequence of planting trees in a flood management strategy?
Reduced soil erosion and better habitats for wildlife
What is a drawback of soft engineering methods?
Less land available for farming
What is a potential risk of embankments?
Severe flooding if water rises above their level or if they break
