River Landscapes in the UK Flashcards
abrasion
rocks carried along by the river wear down the river bed and banks
attrition
rocks being carried by the river smash together and break into smaller, smoother, rounder particles
Cross profile
the side to side cross section of a river channel and/or valley
Dams and reservoirs
A barrier (made on earth, concrete or stone) built across a valley to interrupt river flow and create a man-made lake which stores water and controls the discharge of the river
discharge
the quantity of water that passes a given point on a stream or river-bank within a given period of time
embankment
raised banks constructed along the river; they effectively make the river deeper so it can hold more water. They are expensive and do not look natural but they do protect the land around them
estuary
the tidal mouth of a river where it meets the sea; wide banks of deposited mud are exposed at low tide
flood
occurs when river discharge exceeds river channel capacity and water spills out of the channel onto the floodplain and other areas
floodplain
the relatively flat area forming the valley floor on either side of a river channel, which is sometimes flooded
floodplain zoning
attempts to organise the flood defences so that land that is near a river and often floods is not built on
this could be used for pastoral farming, playing fields
flood relief channel
building new artificial channels which are used when a river is close to maximum discharge
they take the pressure off the main channels when floods are likely, reducing flood risk
flood risk/rate
the predicted frequency of floods in an area
flood warnings
providing reliable advance information about possible flooding
flood warning systems give people chance to remove possessions and evacuate areas
fluvial process
processes relating to erosion, transport and deposition by a river
gorge
a narrow, steep sided valley
hard engineering
involves building entirely artificial structures using various materials such as rock, concrete and steel to reduce, disrupt or stop the impact of river processes
hydraulic action
the force of the river against the banks can cause air to be trapped in the cracks and crevices
the pressure weakens the banks and gradually wears it away
hydrograph
a graph which shows the discharge of a river, related to rainfall, over a period of time
interlocking spurs
a series of ridges projecting out on alternate sides of a valley and around which a river winds its course
lateral erosion
sideways erosion by a river on the outside of a meander channel
it eventually leads to the widening of the valley and contributes to the formation of the floodplain
levee
embankment of sediment along the bank of a river
it may be formed naturally by regular flooding or man-made to protect against flooding
long profile
the gradient of a river, from its source to mouth
meander
a pronounced bend in a river
oxbow lake
an arc-shaped lake which has been cut off from a meandering river
precipitaion
moisture falling from the atmosphere
rain, hail, snow, sleet
saltation
particles bouncing down the river bed
soft engineering
uses the natural environment surrounding a river, using schemes that work with the rivers natural processes
usually much cheaper and more sustainable
solution
soluble particles are dissolved into the river
straightening
removing meanders from a river to make the river straighter
allows the river to carry more water quickly downstream, doesn’t build up, less likely to flood
suspension
fine solid material held in the water while the water is moving
traction
the rolling of boulders and pebbles along the river bed
vertical erosion
downward erosion of a river bed
waterfall
sudden decent of a river or stream over a vertical or very steep slope in its bed
Characteristics of waterfalls
steep drop
plunge pool
overhanging hard rock
Characteristics of interlocking spurs
steep gradients.
project from alternate sides of the valley.
separated by a narrow valley floor, which is mainly taken up by the river channel.
Characteristics of gorges
narrow, steep-sided valleys with bare, rocky walls
fast-flowing water
located downstream of a waterfall.
Formation of waterfalls
form where a river flows over alternating bands of hard and soft rock, with the softer rock eroding faster
undercutting creates an overhang
hard rock collapses
plunge pool forms
retreats upstream
Formation of interlocking spurs
If there are areas of hard rock which are harder to erode, the river will bend around them
This creates interlocking spurs
Formation of gorges
formed by the retreat of waterfalls
Characteristics of meanders
bends in the river
lateral erosion
slip-off slopes
river cliffs
migration
oxbow lakes
Characteristics of oxbow lakes
horseshoe-shaped
middle course of river
vegetation - can become a marshland
Formation of meanders
increased velocity on the outside bend
leads to erosion - like hydraulic action and abrasion
deposition on the inside of the bend - water slows down due to friction with the riverbed and deposits sediment, forming a slip-off slope
Formation of oxbow lakes
meander formation
neck narrowing
breakthrough during flood
meander abandonment
oxbow lake formation
deposition and drying
Characteristics of levees
raised riverbanks
steep side facing the river
gentle sloping side facing the floodplain
flat top
composed of the sediment deposited by the river, including gravel, sand, and silt
Characteristics of floodplains
flat land
rich in nutrients - fertile soil
flood risk
levees
Characteristics of estuaries
found at the mouth of the river
contain a mix of freshwater and saltwater
as the river slows down and meets the sea, it deposits sediment, forming mudflats and salt marshes
tidal, therefore water level fluctuates with the tides
estuaries are important habitats for a wide variety of wildlife
mudflats exposed at low tide and submerged at high tide, saltmarshes develop where vegetation grows
Formation of levees
a river floods and water spills out of its channel and onto the floodplain
as the water moves onto the floodplain, its velocity (speed) decreases due to increased friction with the land
sediment is deposited
over time, with more floods, more sediment is deposited along the riverbanks, building them up into levees
Formation of floodplains
Meanders erode the river banks, widening the valley floor
When a river floods, it loses energy and deposits the sediment it was carrying onto the floodplain
As meanders migrate downstream, they continue to erode and deposit, further widening the floodplain.
Over many years, repeated flooding and deposition build up a thick layer of sediment, creating a wide, flat floodplain
Formation of estuaries
rising sea levels
become sediment traps
velocity decreases, causing the river to deposit the sediment it is carrying
The deposited sediment builds up, forming mudflats.
Over time, vegetation can colonize the mudflats, leading to the formation of saltmarshes
What are the benefits of hard engineering?
dams and reservoirs: dams trap water, creating reservoirs that can release water in a controlled manner, reducing the risk of downstream flooding
embankments: increases channel capacity
straightening channels: removing meanders speeds up the water flow, allowing large volumes of water to pass through quickly, reducing the risk of flooding in the straightened area
flood relief channels: diverts excess water, preventing flooding
other: hydroelectric power, water storage, recreation
What are the economic costs of hard engineering?
expensive to build
maintenance costs and repairs
potential failure, leading to catastrophic flooding and even greater costs
What are the environmental costs of hard engineering?
habitat destruction
ecosystem disruption
sediment deposition issues - dams trap sediment, reducing the amount available downstream, which can lead to decreased soil fertility and erosion problems
visually unappealing
What are the social costs of hard engineering?
displacement of people
loss of farmland
reduced water quality - unsuitable for drinking or irrigation
increased flood risk downstream
What are the different methods of hard engineering?
dams and reservoirs
channel straightening
embankments
flood relief channels
What are the different methods of soft engineering?
flood warnings and preparation
flood plain zoning
planting trees
river restoration
How do physical factors affect flood risk?
Physical factors like heavy or prolonged rainfall, steep slopes, impermeable rock, and saturated soils significantly increase flood risk by promoting faster runoff and reducing the time it takes for water to reach river channels
How do human factors affect flood risk?
Human activities like urbanization, deforestation, and agricultural practices significantly increase flood risk by altering natural drainage patterns, increasing surface runoff, and reducing the ability of land to absorb water
What are the benefits of soft engineering?
reduced environmental impacts (Preserves Natural Habitats, Sustainable Solutions, Improved Water Quality)
cost effective (lower initial cost, reduced maintenance cost)
flood risk reduction
What are the economic costs of soft engineering?
initial and maintenance costs can be expensive e.g. river restoration, flood warning systems
Floodplain Zoning restricts development in flood-prone areas, can lead to lost opportunities for economic development and housing.
Afforestation: planting trees to increase interception and infiltration can lead to the loss of farmland
What are the environmental costs of soft engineering?
Altered Landscapes and Habitats
Habitat Loss
Changes in River Flow
Loss of Grazing Land
What are the social costs of soft engineering?
restricted development (housing, planning permission issues)
impact on livelihoods (agriculture, tourism)
limited access
What are the different physical factors that affect flood risk?
precipitation
relief/topography
geology
soil type
vegetation
drainage basin characteristics
What are the different physical factors that affect flood risk?
urbanization (impermeable surfaces, drainage systems, reduced green spaces, building on floodplains)
deforestation (soil erosion, reduced interception)
agricultural practices (overgrazing etc)
