1.4 River Landscapes and Processes (Paper 1) Flashcards
(114 cards)
<p>Define <strong>long profile</strong></p>
<p>The change in the<strong>gradient</strong>of the river course from the upper course to the lower course</p>
<p>What is a '<strong>crossprofile</strong>'?</p>
<p>A cross section of the river - this shows a 'slice' of the river valley and channel</p>
<p>What is a<strong>V-Shaped valley</strong>?</p>
<p>A valley with steep sides and a narrow bottom that has been formed by erosion</p>
<p>What is a<strong>tributary</strong>?</p>
<p>A smaller river or stream flowing into a larger river</p>
<p>What is a<strong>confluence</strong>?</p>
<p>The point where two rivers meet</p>
<p>Define '<strong>load</strong>'</p>
<p>The amount of material carried by a river</p>
<p>What is '<strong>sediment</strong>'?</p>
<p>Material such as sand and clay that is carried by a river</p>
<p>What are the<strong>characteristics</strong>of the<strong>upper course</strong>of a river?</p>
<ul> <li>Steep gradient</li> <li>Narrow v-shaped valley</li> <li>Narrow/shallow river</li> <li>Large angular sediment load</li> <li>Mostly erosion taking place</li></ul>
<p>What are the<strong>characteristics</strong>of the<strong>middlecourse</strong>of a river?</p>
<ul>
<li>Shallower gradient compared to upper course</li>
<li>Asymmetricalvalley cross section</li>
<li>Deeper river</li>
<li>Smaller/rounded load</li>
<li>Balance betweenerosion and transportation taking place</li></ul>
<p>What are the<strong>characteristics</strong>of the<strong>lowercourse</strong>of a river?</p>
<ul> <li>Very low gradient</li> <li>U-shaped valley</li> <li>Wide/deep river</li> <li>Small suspendedload</li> <li>Mostly depositiontaking place</li> </ul>
<p>Define <strong>erosion</strong></p>
<p>The wearing away of rock by the natural processes of rivers, ice, wind and sea</p>
<p>Name the<strong>4</strong>processes of river<strong>erosion</strong></p>
<ul> <li>Abrasion</li> <li>Attrition</li> <li>Hydraulic Action</li> <li>Solution</li> </ul>
<p>Define '<strong>hydraulic action</strong>'</p>
<p>Fast flowing water pushes air into cracks and the force of this causes the channel to break up over time</p>
<p>Define '<strong>abrasion</strong>'</p>
<p>Sand and pebbles are dragged along the river bed, wearing it away</p>
<p>Define '<strong>attrition</strong>'</p>
<p>Rocks and stones wear each other away as they knock together</p>
<p>Define '<strong>solution</strong>' (erosion)</p>
<p>Rocks such as limestone are dissolved in acid rainwater</p>
<p>Define '<strong>transportation</strong>'?</p>
<p>The movement of eroded material by natural processes such as wind, rivers and sea</p>
<p>What are the<strong>4</strong>processes of <strong>transportation</strong></p>
<ol><li>Solution</li><li>Suspension</li><li>Saltation</li><li>Traction</li></ol>
<p>Define '<strong>traction</strong>'</p>
<p>Big boulders and stones are rolled and dragged along the river bed</p>
<p>Define '<strong>saltation</strong>'</p>
<p>Stones and pebbles bounce along the river bed</p>
<p>Define '<strong>suspension</strong>'</p>
<p>Smallerparticles andstones (e.g. sand and silt) are carried along in the rivers flow</p>
<p><strong>Define 'solution'</strong></p>
<p>Some material is dissolved into the river water and transported this way</p>
<p>What does '<strong>deposition</strong>' mean?</p>
<p>When a river drops the sediment that it is carrying</p>
<p>Why will a river<strong>deposit</strong>its load?</p>
<ul>
<li><strong>Drier weather</strong>(less water so less energy)</li>
<li><strong>River slows in speed</strong>(less speed so less energy e.g. inside bend of a river)</li>
<li><strong>River floods</strong>(water onto the flood plain and deposits layers fine silt and clay [this is known as alluvium] which is fertile and good for farming)</li>
</ul>
Name the river landforms formed by erosion
- Waterfalls
- Gorges
- Interlocking spurs
Name the river landforms formed by erosion and deposition
- Meanders
- Ox-bow Lakes
Name landforms created by deposition in rivers
- Floodplains
- Levees
Name the landforms found in the upper course of a river valley
- Waterfalls
- Gorges
- Interlocking Spurs
- Rapids
What is a waterfall?
A vertical fall of water where the course of a river is interrupted by a steep drop in the land it is flowing over
How does a waterfall form?
- Water flows over harder rock followed by softer rock
- The softer rock underneath the harder rock will erode over time (hydraulic action and abrasion) creating a step in the river
- The hard rock is undercut by erosion
- Eventually the hard rock will collapse as it is now unsupported creating a deep plunge pool
- The process will continue over time creating a steep sided gorge
What is a gorge?
A steep-sided cut through the landscape formed over thousands of years by a retreating waterfall
What is a plunge pool?
The area of deep water at the bottom of a waterfall, formed by hydraulic action and the grinding of rocks and pebbles
What are 'interlocking spurs'?
'Interlocking' hillsides that look like a 'zip' formation
How are interlocking spurs formed?
In the upper course, rivers aren't powerful enough to erode laterally, so they wind around the hillsides creating a zig-zag shaped flow
Name the landforms found in the middle course of the river
- Meanders
- Ox-bow lakes
Define 'helical flow'?
The corkscrew pattern of flow found in a river
What is a meander?
A pronounced bend in a river
What is an ox-bow lake?
A horse-shoe shaped lake shaped that is formed when a river bend is cut off from the main river and becomes isolated
Explain how an ox-bow lake forms
- The river meanders across the valley and the river is eroding laterally (from side to side)
- The river flows faster on the outside bends and erodes them
- The river flows slowly on the inside bends and deposits material so its course is changing
- Continual erosion and deposition narrows the neck of the meander
- Often during a flood the river will cut through the neck
- The river continues on its straighter path and the meander is abandoned
- New deposition seals off the ends and the cut-off becomes an oxbow lake that will eventually dry up
Name the landforms found in the lower course of a river valley
- Wide floodplain
- Levees
- Deltas
- Estuaries
What are mudflats?
Flat coastal areas formed when mud is deposited by rivers and coasts
What is a levee?
Natural river embankments found along the river banks They are formed when the river floods and material is deposited along the banks
How is a levee formed?
During a flood, sediment is deposited on the river banks; depositing coarser (heavier) sediment nearer to the river and finer sediment further away
Define 'river discharge'
The amount of water flowing in a river at any one point
Volume × Velocity
List the factors affecting river discharge
- Rock and soil type
- Land use
- Rainfall
- Weather conditions
- Relief
How can you recognise the upper course of a river on an OS map?
- Contour lines are close together
- River crosses lots of contour lines
- Narrow river (thin blue line)
- Spot heights are high numbers
How can you recognise the lower course of a river on an OS map?
- Limited contours or very wide contours (land is flat)
- Wide river that is meandering
- Spot heights are low numbers
Name an example of a river valley in the UK
River Tees
How can you recognise a V-shaped valley on an OS map?
V-shaped contours point uphill and river crosses the middle of the V-shaped contours
Where is the River Tees?
In the North East of England
Where is High Force waterfall?
Close to Forest-in-Teesdale on the River Tees
Where is the mouth of the River Tees?
Middlesbrough. It flows into the North Sea
Where is the source of the River Tees?
Pennine Hills near Cross Fell (height 893m)
Name 4 physical causes of flooding
- Heavy/Prolonged precipitation
- Snowmelt
- Relief (steep slopes)
- Geology
Name 3 human causes of flooding
- Urbanisation
- Deforestation
- Agriculture
What is a hydrograph?
A graph showing how a river responds to a storm, showing the rainfall and discharge over time
What is a 'flashy' hydrograph?
A hydrograph with a short lag time and a high peak discharge
What is a 'flat' hydrograph?
A hydrograph with a long lag time and a low peak discharge
How is river discharge measured?
Volume × Velocity
Cubic metres per second (cumecs)
Which factors influence the shape of a flood hydrograph?
- Basin size
- Drainage density
- Rock type
- Land use
- Relief
- Rainfall intensity
What is 'lag time'?
The time between peak rainfall and peak discharge on a hydrograph
What is antecedent rainfall?
The amount of rain that has already fallen prior to a specific event
Define 'interception'
Leaves and tree branches catch rainfall and prevent it from running into the river
Define 'infiltration'
Rain that soaks into the top layers of the soil and rock below
What is impermeable rock?
Rock which water is not able to flow through
What is permeable rock?
Rock which water is able to flow through
Define surface run off
Water runs over the top of ground which is very hard (i.e. baked soil or concrete) or very wet (saturated) ground.
Surface run off occurs when no water can infiltrate into the ground
What is hard engineering?
Building structures to deal with natural hazards, such as dams to prevent flooding
Name a range of hard engineering stategies used to manage river flooding?
- Reservoirs and dams
- Channel straightening
- Embankments
- Flood relief channels
What is soft engineering?
Soft engineering involves adapting to natural hazards and working with nature to limit damage. For example, planting trees to limit flood risk
Name a range of soft engineering strategies used to manage river flooding?
- Afforestation
- Land use zoning
- River restoration
- Wetland restoration
- Flood warnings
How do dams regulate water flow?
Durings periods of high rainfall, water is stored in the dam
Water is released when rainfall is low
Why is building dams controversial?
- They are very expensive
- Land is flooded to create the reservoir
- People are relocated to make way for the dam
What are the benefits of dams?
- They are multi purpose - so they can be used to generate HEP as well as manage river flow
- They are affective holding back water in times of potential flood
- They are long lasting
Most dam schemes are multi-purpose. What are their main functions?
- Flood prevention
- Irrigation
- Water supply
- Hydro-electric power generation
- Recreation e.g. sailing
What is channel straightening?
Cutting through meanders to create a straight channel to speed up water flow
What are the advantages of channel straightening?
It moves water out of an area quickly as water passes through a straight channel quicker than a meandering channel
Why is channel straightening problematic?
It may increase the risk of flooding further downstream
What are river embankments?
Raised riverbanks which allow the river channel to hold more water and prevent flooding
What are the advantages of river embankments?
Embankments increase the volume of water that the river can hold, reducing the risk of flooding
What are the problems with embankments?
Not always effective. Water can rise above the embankments, causing flooding
What are flood relief channels?
A man-made river channel constructed to by-pass an urban area
What are the benefits of flood relief channels?
River discharge can be controlled by using gates to control water levels
What are the disadvantages of flood relief channels?
Increased levels of flooding could occur where the diverted water re-enters the river
How does floodplain zoning work?
- It restricts different land uses to certain locations on the floodplain
- Expensive/important landuses are placed further away from the river e.g. housing and industry
- Low value uses are placed close to the river e.g. pasture and parkland
What are the advantages of flood plain zoning?
Consideration into the landuse around the river is taken which means concrete surfaces are not used, reducing impermeable surfaces close to river. Less damage occurs as important facilities are located futher away
What are the disadvantages of flood plain zoning?
It limits the uses of land closes to a river
It is almost impossible to use flood plain zoning on land that has already been built on
What is river restoration?
Making the river more natural. For example:
- When rivers have previously been artificially starightened they are returned to their original course.
- Removing levees so that the river floods naturally
The purpose of this is to prevent flooding further downstream
What are the benefits of river restoration?
- Less risk of flooding downstream
- Limited maintenance needed
- Creates habitats for birds
What are the problems with river restoration?
- Flooding can increase
- Major floods are more likely unless planning takes place
How does afforestation help manage river flooding?
Planting trees to intercept and absorb water reduces surface run off
Who issues flood warnings in England and Wales?
The Environment Agency
What are the 3 levels of flood warnings?
- Flood Watch
- Flood Warning
- Severe Flood Warning
What would people be encouraged to do by the Environment Agency to prepare for a flood?
- Plan what to do eg. move possessions upstairs
- Use flood gates to prevent water entering their property
- Use sandbags to keep floodwater away from buildings
Name a example of a flood management scheme in the UK
Morpeth Flood Scheme - River Wansbeck
Why does the town of Morpeth, on the River Wansbeck, need a flood management scheme?
- The river valley is narrow and steep leading to high levels of suface run off in times of high rainfall
- Increasing levels of wetter weather exacerbate the flood risk
- High cost of damage from previous flood events
What was done to manage flooding in Morpeth?
- Lowford Bridge tree catching poles - to cacth debris and prevent it flowing downstream, and blocking bridges
- Mitford Dam - can hold back 1.3 million cubic metres of water, reducing flow to town centre
- Improved existing flood defences
- Flood gates set up - and designated flood warden to close gates at times of flood
Describe the social issues (+ and -) arising from the Morpeth flood management scheme
+ Local people were consulted over defences
+ Residents on Mitford Housing Estate were paid compensation for Mitford Dam being built
-... this caused conflict with other locals
- Some houses on Wansbeck street (close to river) have not been defended
Describe the economic issues (+ and -) arising from the Morpeth flood management scheme
-/+ The Morpeth Flood Action Group are working to reduce insurance premiums for people living near the river
- Cost of the scheme was £25 million, £5 million over the original estimate
Describe the environmental issues (+ and -) arising from the Morpeth flood management scheme
+ In Jan 2016, Storm Desmond brought high river levels to the town. The flood defences held up and the flood gate was used.
+ The native white clawed crayfish has been moved by hand to a new location in the River to ensure it is conserved.
+The flood walls were designed so they fitted the historic image of the town
What are the 3 types of weathering?
- Chemical Weathering
- Biological Weathering
- Mechanical Weathering
What is biological weathering?
Biological weathering is when roots of plants gorw inside rocks, forcing the rocks to crack and break apart
What is Chemical Weathering?
Chemical Weathering is when the slightly acidic rainwater causes a chemical reaction on the rock, which wears it down
What is Mechanical Weathering?
Mechanical weathering is when water gets into the cracks of rock. As temperatures drop, the water expands which cracks the rock. This continually occurs until thethe rock is completely broken off
How are Gorges and Waterfalls formed?
- A river erodes the less resistant rock, creating a notch in the softer rock, which creates a river rapid
- Overtime, more of the softer rock gets eroded leaving the hard rock sticking out above the soft rock
- The height of the drop increases as the water erodes the soft rock at the bottom, creating a waterfall
- The process fo undercutting occurs, where the less resistant rock starts to be eroded underneath the hard rock
- The overhanging hard rock eventually collapses due to there not being enough support
- The hard drock and the soft rock base erode through abrasion which creates a plunge pool
- This keeps continuing and the waterfall receeds upstream and if the process is repeated multiple times, agorge may form
What are flood plains?
Flood Plains are wide areas of flat land that surround a river in their lower course at the bottom of a vally. These areas are succeptible to flooding
What are point bars?
Point Bars are a cresent-shaped landform that is made up of deposited material that accumulates on the inside bend of a river meander
How are Ox-Bow Lakes formed?
- As erosion continues, the meanders in the river get closer to each other and create a swan's neck meander - a small piece of land between bends
- During a flood, high energy water will breach the neck of the meander
- This makes the river flow straighter and have a faster course
- Over time, deposits fill in the meander bends
- The meander cuts off from the river, which forms an ox-bow lake
What does lateral erosion do?
Lateral erosion makes the river wider
Which part of a river does lateral erosion occur?
Lateral Erosion occurs in the lower and middle courses of a river
What does vertical erosion do?
Vertical erosion makes the river valley deeper
Where does vertical erosion occur?
Vertical erosion occurs in the upper courses of a river
How are flood plains formed?
Flood Plains are formes by meander migration close to the mouth of the river
