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Rivers, Coasts, Geology Notes
Geographical Perspectives (ENV-4010Y)
University of East Anglia
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Rivers, Coasts and Geology notes
Rivers
Lesson 1: Profile of a river
Rivers are split in three sections: the upper course, middle course and lower course Features of the upper course are: Steep valleys Shallow depth Velocity at its slowest Very steep gradient, mountainous Narrow channel, river at its narrowest here Waterfalls, interlocking spurs and V-shaped valleys River source Small discharge
Features of the middle course are: Depth increasing Gradient decreasing, less steep Meanders and floodplains, Ox-bow lakes Velocity increasing Channel shape beginning to flatten, steep sides decreasing Discharge increasing
Features of the lower course are: Deepest point of river Velocity at its fastest Discharge is very large Meanders, floodplains, levees and deltas Channel shape mostly flat, sloping sides Shallow gradient Mouth
Features of a river as a whole:
River Severn (Caste study 1)
River Severn is the longest river in British Isles-354km Flows through Wales, Gloucester, Worcestershire, Shropshire Large towns developed on the banks on Rivers Tributaries- River Stour, River Worfe
Upper course features Starts 74km above sea Plynlimon Hills(Source) Waterfalls V-shaped valleys Middle course features Floodplains Tewkesbury Meanders Forests Lower course features Mouth- out into British Channel Widest point, 13km Large river estuary- wet lands
Floodplains & Levees (Middle & Lower course, Formed by Erosion & Deposition) Formed when a meander laterally erodes. When they reach the edge of the floodplain they erode the valley side When the river floods it deposits silt creating a flat floodplain Eventually layers build up forming a thick deposit of fertile alluvium(alluvium is a sediment deposited by a river when it floods) The heavier and coarser sediments are first deposited at river’s edge creating embankments called natural levees
Erosional Processes that occur along a river Abrasion- other pebbles held by the waves flung at a cliff Attrition- Pebbles bashing into each other, gradually get smaller and smaller Hydraulic Action- The force of sea water forces air into joints and faults in the rock, gradually wearing the rocks down. Corrosion- Acidity in water dissolving the rocks
River processes A river carries rocks in four ways: Suspension- small particles of sand and silt through the flow. Traction- large stones rolled along river bed. Saltation - small stones bounced along the river bed. Solution- Dissolved minerals within water carried by the flow
Lesson 3- River Landscapes: Slope Processes, Mass Movement and Geology
Mass Movement- The downward movement or sliding of a material under the influence of gravity Weathering- The breaking down of rocky surfaces when they are exposed to the atmosphere
Examples of Weathering: Biological Cracks in rocks can be penetrated by grass and roots in search of water and nutrients As they grow roots they expand and force cracks, breaking the rock into pieces Freeze thaw
In Winter, cracks in rocks fill with water which then freeze and expand creating bigger cracks Overtime pieces of rocks break away forming scree Chemical A change or decay of soil rock Rainwater mixes with acids in the soil which can dissolve alkaline rocks such as Limestone
Examples of Mass Movement: Soil creep: Soil particles slowly move down a slope under gravity and gather at the bottom of the valley sides River may erode this soil taking it downstream Slumping Occurs when bottom of valley side is eroded by the river Makes the slope steeper, material slides downwards in a rotational manner Caused by heavy rain making the soil and rock heavier, more likely to slip down to base of river Landslides and Mudflows Rapid examples of mass movement either soil creep or mass movement Likely to be triggered by a natural hazard
Mass Movement and Slumping affect the shape of a valley as it leads to smaller river width as the sediment becomes a bank Soil creep also affects the shape, Soil creep next to a river leads to river terraces on the side of a V-Shaped Valley.
Lesson 4: Flood Hydrographs, physical and human causes of flooding
Hydrological Cycle- The process of water travelling from Earth’s surface to the atmosphere and back to the ground again Examples of water stores: Clouds, oceans, groundwater storage All transfers in the water cycle: Evaporation Condensation Transpiration- Process of water movement through a plant, roots absorb water, then give off water vapour through leaves Sublimation- Solid to gas
A flood plain can be seen on an ordnance survey map, during the middle course the flat land shows were the rivers most likely to flood creating a floodplain Steep contour lines show the upper course, shows where waterfalls would be
Lesson 6- The causes and impacts of flooding
Tewkesbury Flood occurred in 2007 Physical causes of flooding Catchment size- drains 6900km Rainfall conditions, July 2007 wettest day Human causes of flooding Location is surrounded by rivers Large housing built on floodplains, pushes water into non-floodplain areas Impermeable surfaces- water can’t infiltrate, water trying to drain away which could get clogged up Poorly built and maintained drains causes pluvial flooding, intense rainfall overwhelming drainage Impacts of flooding Economic No insurance couldn’t sell homes 800 properties effected Cost £40,000 and took 8 months to get their homes back Social 150 homes without water 5,000000 bottles were handed out Environmental Bad smells Sewage pipes contaminated
Sussex Wealds
Lesson 7: Management of Floods Examples of Soft Engineering Methods: Flood Warnings- Rivers watched for rising water levels P = People who live downstream receive warning messages so they can prepare or evacuate N =Sometimes not possible to give warnings, not much preparation time Afforestation- Trees are planted in the drainage basin P= Trees intercept rainfall, less water reaching river. Looks attractive, creates wildlife habitats N= Land can’t be used for other activities
Flood Plain Retention- Areas on a flood plain which are allowed to flood P= Safe place for flood water to go, inexpensive and natural environment unspoilt N= Flood plain can’t be used any other way
Zoning land- Government allocate areas of land to different uses, according to level of flood risk P= Buildings put in low risk areas, Parks and Leisure are in high risk areas to reduce cost if flooded N= Not good place for housing, poor accessibility
Examples of Hard Engineering Methods: Leeves- Man made embankments on a river P= Cheap, reduces flood risk, can hold a lot of water N= If they fail causes huge flooding, very expensive: cost per km £1million
Flood walls- Walls built as banks for flooding P=Cheap to build and maintain, good for areas where space is limited N= Can cause flooding downstream, walls not aesthetically pleasing
Dredging- Digs up material from river bed, increasing capacity of water P= Reduces flood risk, maintains river depth and speed up flow N= Needs to be done every year, speedy flow is a risk downstream, Expensive
River Straightening - River coarse straightened by cutting meanders and building artificial meanders P= Useful for city centre locations where space is limited
Formed from molten rock(magma) that has cooled and solidified Most igneous rocks are resistant to erosion E. Granite, formed from magma cooling deep underground, Contains crystals of quartz and its very resistant
Sedimentary Formed from sediments eroded and deposited by rivers, the sea or sea bed. Some are resistant whilst others easily crumble E. Clay, formed from mud deposits from rivers, soft and easily crumbles. Metamorphic Formed from sedimentary rocks that are heated/compressed from lava/magma. Heating and compression harden them and make them resistant. E. Marble, Formed from heated limestone, very resistant.
Lesson 2- Geology processes, UK Geology
Factors which affect the UK landscape:
Glaciation In the last 500,000 years Britain was covered by ice Most recent glaciation was 10,000 years ago. Glaciers and ice sheets scoured the landscape, wearing rocks away and forming glacial landscapes. During cold periods, ice would’ve been hundreds of metres thick Material eroded by the ice was left behind as glaciers retreated.
Geology The UK used to be covered in tropical seas, would’ve been similar to the Great Barrier Reef in Australia. Tropical fish and coral thrived there But as they died their skeletons fell to the sea floor forming horizontal layers(strata) As skeletons of dead animals fell they crashed those beneath, squeezing out water which compacted them into a rock Later layers of rock(strata) were deposited on top of limestone, the rocks vary in hardness as some erode easier than others
Tectonic Processes
As sand is pushed up, some rocks snap as earthquakes disturb the layers of rock so they are tilted Under plates convection currents uplift rocks below the sea forming land. In over 300 million years the Eurasian plate has moved north from the tropics.
Lesson 3- Impact of human and physical factors on UK landscapes
Weathering- Physical, chemical or biological breakdown of solid rock by the action of weather (frost or rain) or plants. Slope Processes- Processes caused by the mass movement of earth and soil leading to rock falls, landslides and soil creep. Post Glacial Processes- Erosion that has happened following on from the last ice age in the UK.
Impacts of these processes in the UK
Lake District Loose rock fragments(scree) make the ground rough. Scree consists of angular rock pieces created by freezethaw actions. Every winter more scree is added to mountains. ( Weathering) Lake District was once covered by glaciers. These created deep U-shaped valleys and hollows which are filled by lakes. Rivers replaced glaciers, they deposit fertile alluvium, good for farming. ( Post Glacial Processes) Landslides are common as it’s the UK’s wettest region, Rain adds weight to the weathered rock so it slides easily. ( Slope Processes) Rock falls are common in area of steep sides, Scree fragments are unstable and easily move which is a hazard to hikers. (Slope Processes)
Sussex Wealds Slope processes slower here than in Northern England, as its more upland Northern. Most common action is soil creep. Caused by rain dislodging soil particles and the increased weight of the earth moving soil downwards. ( Slope Processes) As Southern England is warmer than Lake District, it is affected by different sub-aerial processes. Solution affects chalk surfaces, wearing it away. ( Weathering)
Coasts
Lesson 1- How are coastal landscapes influenced by geology
Processes of erosion: Attrition- Pebbles bashing into each other, gradually get smaller and smaller Abrasion- other pebbles held by the waves flung at a cliff Corrosion- Acidity in water dissolving the rocks Hydraulic Action- The force of sea water forces air into joints and faults in the rock, gradually wearing the rocks down. The formation of bays and headlands at a discordant coastline The waves are eroding, as the hard rocks are too resistant and can’t be eroded the waves focus on the softer rocks as they wear away easily As soft rocks wear’s off it creates a bay, the less eroded hard rocks stay put and create a headland A discordant coastline is where bands of differing rock types run perpendicular to the coast, where the hard and soft rock is. A concordant coastline occurs where the bands of differing rock types run parallel to the coast, where the soft rock is
Formation of coves at a concordant coastline
Coastal features at a headland
Formation of caves, stacks and arches
Caves- occur when waves force their way into cracks in the cliff face. As the water contains materials like sands, it grinds away at the rock until it becomes a cave, hydraulic action is the predominant process. Arch- the pressure of the waves can erode the back of the cave which forms an arch Stack- After continued erosion by destructive waves, the arch collapses and becomes a stack.
Formation of wave cut platforms Wave-cut platforms are created as cliff retreats, due to weathering at the top of the cliff and sea erosion at the base of the cliff.
Lesson 4- Human activities and their impact on the coast and coastal management
Dawlish- South west England, On the coastline , in Devon. Train track damaged by a high tide, destructive waves
Summary of Dawlish Article Rising sea levels becoming a threat, as Britain is an island nation a high amount of important infrastructure from ports and power stations lie along coasts Vital transport link between Devon and Cornwall, several sections have been washed up 4-6 weeks of repair The most severe damage in its 178 years of service meaning rising sea levels would cause months of distruption Coastal flooding most likely when strong storms and low atmospheric pressure combine to drive storm surges towards the coast. This^ with high tides= chaos With sea levels set to rise these extreme events can become more frequent Hard engineered sea walls have been built to protect coastal communities. One of the third of the total coastline of England and Wales is protected Coastal flooding is difficult to predict due to storminess and frequency of surges Flood defences very expensive, as sea levels rise it requires more and more investment. Re-routing the line would be too costly but if it was to occur it would benefit access to employment, increased business opportunities and quality of life Without investment the transport services will inevitably collapse These regional and local lines are being ignored, these lines are heavily relied upon. By investing in them it will improve the resilience of Britain’s transport infrastructure overall
Cowden, Cliff House Farm Located North-East of Yorkshire Mr and Mrs Mars lost 3M of their land in 3 MONTHS Can’t get any insurance on their property
The fastest eroding stretch of coast in Europe Lost their business, pig farming
Hard Engineering- Involves structures built along the coast/base of the cliff. E. Sea walls, groynes. They can have impacts elsewhere along the coast
Soft Engineering- Is designed to work with natural processes in the coastal system to try to manage and not necessarily prevent erosion.
Methods of Hard Engineering:
Recurved Sea wall Concrete wall curved under the side Advantages: Deflects power of waves Sea walls reflect rather than absorb wave energy Prevents erosion Disadvantages Very expensive, up to £2 Reflected waves can undermine the wall which means it will eventually collapse
Rock Armour Large boulders on the beach Advantages: Decreases waves’ force Absorbs wave energy within the gaps between rocks Relatively cheap Uses natural materials, rocks Disadvantages Environmentally ugly Can be undermined and removed by waves due to the washing away of sand beneath
Larger beach encourages tourism, benefitting local shops and hotels Businesses will grow creating opportunities, multiplier effect Disadvantages: Increases erosion further down coasts If beaches become smaller, fewer tourists leading to unemployment meaning buisnesses have less money to invest in the area, negative multiplier effect Expensive, £5,00-£6,
Methods of Soft Engineering
Cliff Drainage Drains cliff water and reduces rotational cliff slumping Advantages: Cheap Is underground so doesn’t spoil aesthetic view Disadvantages: Doesn’t protect the cliff from wave action Looks ugly when cliff erodes
Beach Nourishment Adds more sediment to the beach, the larger the width of the beach the less erosion on the cliff line Works with long shore drift which transports the sediment overtime Advantages: Cheap Protects that particular location Larger beach= more tourists Disadvantages Sediment was taken from elsewhere, increasing erosion along other coastlines
Lesson 6: Coastal flooding and Climate change
Rivers, Coasts, Geology Notes
Module: Geographical Perspectives (ENV-4010Y)
University: University of East Anglia
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