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River Case Studies
Fichas del conjunto (41)
- 1Draix Watershed-SE FranceTwo areas: Brusquet and Laval.
Brusquet- 87% forest cover
Laval- 22% forest cover
Floods in 1991 show that discharge in the Laval region was 1,000litres/s, whereas in the Brusquet region it was 200 l/s - 2Plynlimon, WalesSitka Spruce Tree- 36% Interception, whereas Larch (deciduous conifer) 20%.
- 3Konto, East JavaIt was found that the conversion of forest to tea, rubber and cocoa plantations increased stream flow. However, terraced rice paddies are constructed to contain water and this reduces the amount of surface runoff.
- 4River Eden Flood in Carlisle in 2005In the Skiddaw area, the rocks types of the drainage basin include volcanic, whereas in the Vale of Eden area the majority of the rocks are limestone. In the Skiddaw area, the maximum flow was 1,500 m3/s and in the Vale of Eden area, the maximum flow rate was 100m3/s.
- 5Carson Desert Basin, NevadaIn August, when it is 29 degrees Celsius, it rains 13mm, the the discharge is 0.07 cumecs. In January 17mm, 7 degrees Celsius and 0.73 cumecs.
- 6Long Profile-River TeesWhin Sill (volcanic intrusion) lies across the path of the river Tees preventing the graded profile. Cow Green reservoir stores the winter floodwater from the Pennines, so it is the base level for the upper part of the course.
- 7Long Profile- Zambezi RiverTough igneous basalt and limestone prevent graded profile. Kariba dam created new base level for upper course and affected discharge
- 8Meander Case Study:River Nile- Longest Meander in the world. Meanders through 10 different countries and has a length of 4,300 miles.
- 9Delta Case Study:Mississippi- Only major delta solely determined in shape by sediment deposition. It delivers 450 million tonnes of sediment into the delta annually.
Nile Delta- Construction of the Aswan Dam has limited growth of Delta and has shrunk Delta from 7 branches to 2 branches. - 10Levee Case Study:Flanking both sides of the Sheyenne River are ridges of sand deposited during flooding. Vegetation growth on top of levees stabilizes the levees.
- 11Floodplain Case StudyMississippi Floodplain, Louisiana- 5.6 miles across
- 12Braided Streams ExampleExample: Raika River in NZ- mean flow of 203 cubic metres.
- 13V Shaped Valley Case StudyHeatherhope Valley, Northumberland- Steep decrease from 350m to 150m in ½ km.
- 14Interlocking Spurs Case StudyUsway Burn, Northumberland. Made up of Cheviot Volcanic Group Rock (Igneous)
- 15Rapids Case StudyManitou Rapids on the Rainy River, Minnesota. Igneous intrusions and glacial deposits.
- 16Pothole Example:Bourke’s Luck Potholes, Blyde River Canyon, South Africa. Treur river joins Blyde River. Forces of the water in these two rivers, combined with the particles or sand and rock wears potholes in the sandstone bedrock.
- 17Waterfall Case Study:Ribbon Falls, Grand Canyon, Yosemite National Park. It is 491m Tall.
- 18Knickpoint ExampleDevil’s Bridge, Ponterwyd- Original knickpoint that would have existed at Devil’s bridge retreated upstream to form a series of rapids close to Ponterwyd, it falls 550m in 45km.
- 19Entrenched Meander Example:River Wear, Durham. Drops from 200m to 0m very quickly, giving steep sides, as there is little opportunity for lateral erosion to occur giving them their symmetrical shape
- 20Ingrown Meander ExampleRiver Wye More gradual decrease from 300m to 0m, forms river cliff and valley side instead of two cliffs, due to slower vertical erosion where lateral erosion can take place as well.
- 21River Terraces ExampleThames’ River terraces around London due to isostatic uplift after the last ice age in the Pleistocene. Taplow terrace is 15m above the river and Boyn Hill Terrace is 320m.
- 222005 River Eden Carlisle Case Study: Human CausesCarlisle is a large built-up area, with impermeable concreate and tarmac surfaces and little soil or vegetation.
Drains and sewage systems overflowed in some areas- becoming a source of flooding themselves. 25% of the flooding problems were associated with overflowing drains. Defences (flood walls) not able to withstand 1 in 170 year event. Ineffectiveness of zoning of recreational spaces through the city - 232005 Carlisle Case Study: Physical CausesThe drainage basin of the River Eden is very large so it catches a large volume of rainfall. Some parts of the basin have steep sides. There are many streams that drain quickly into the river. There was heavy rainfall on the 6th January, for 36 hours. 200mm of rainfall was recorded (equivalent of 4 months rain). Rain fell on saturated ground so the water didn’t soak onto the ground but ran straight off into the river. This caused a very high peak discharge (over 1520 cumecs) compared to an average of 52 cumecs. Gales up to 120mph, made trees fall into the river channels and drains.
- 242005 Social Effects of the Carlisle Floods3 people died. Over 3,000 people were made homeless for up to a year. Living in temporary accommodation caused disruptions in travel in post. Children lost out on education-Newman catholic school didn't reopen until easter. Increase in stress related illnesses, 1 suicide.
- 25Economic Impacts Carlisle FloodsIt took about a year to repair the damage to homes. It cost over £100 million. 350 businesses had to shut down as there was no electricity. United Biscuits flooded with 3m of water that caused over £5 million damage. 33 people lost jobs. 70,000 homes had no power. 80 buses were destroyed. Roads and Bridges damaged e.g. Warwick Road
- 26Environmental Impacts of 2005 Carlisle FloodsIncreased river bank erosion. Rivers polluted with rubbish and sewage. 1,150 trees uprooted. Loss of biodiversity and habitats. Roads and bridges closed for 2 days.
- 27Bangladesh Flood in 2004 Human CausesThe growth of urban areas, due to migration also increased surface runoff
Deforestation had occurred in the Himalayas meaning less rainfall was intercepted, which increased discharge.
Collapse of earth dams in India caused further flooding. - 28Bangladesh Physical CausesThe long duration of heavy rainfall completely saturated the soil, increasing surface runoff and discharge
It has very flat slopes so it is prone to flooding. About 71% of the country is exposed to flooding. 8 extreme floods in the past century, affecting 50% of the land area.
There was heavy rainfall-Assam has a record 170mm in 24 hours, and 900mm in total
70% of the country less than 1m above sea level.
Monsoon rainfall came suddenly after a very dry, early summer.
Bangladesh experienced heaviest rain in 50 years. - 29Social Effects of Bangladesh FloodsOver 2000 people died. It was high as many people were reluctant to evacuate and many children drowned as they couldn’t swim.
Wells became polluted with sewage, so there was a lack of clean drinking water. Over 100,000 people caught water borne disease.
25 million were made homeless
112,000 houses were destroyed in India, as porous mud bricks became saturated by floodwater
Dhaka was inundated, especially the poorer districts and shanty towns near the river - 30Economic Impacts of the Bangladesh FloodsWidespread loss of livestock. Since 80% of Bangladeshi’s rely on agriculture, many lost their livelihoods
10,000km of roads were destroyed, Landslides blocked roads in the highlands of Nepal and Assam.
The cost of the flood was estimated at $1 billion
Debt increased, both individually (farmers borrowed money for food and seeds) and nationally. - 31Environmental Impacts of Bangladesh FloodsRice destroyed
Agricultural land flooded and contaminated by polluted water
½ million cattle and poultry lost.
Alluvium deposited- soil fertile
Groundwater reserves replenished
Water sources contaminated with sewage - 32Political Impacts of Bangladesh FloodsDamage to schools and hospitals put at $7 billion
In 2006, almost half of the population lived below the poverty line. - 33Solutions to the Bangladesh FloodsUN launched an appeal for $74 million but only 20% arrived by September.
Food supplies, clothing and blankets distributed.Flood shelters have been built and flood warning systems established. Embankments have been built. - 34Background on the Yangtze RiverSeasonal Flooding Common, Five major floods over the last century, flood in 1954 killed 33,000 people. 18 million people had to move.
- 35Hard Engineering on the Yangtze46 dams are planned or under construction. Work began on the 100m high Three Gorges dam in 1994. A reservoir is building up behind the dam. The reservoir catches any flood water. It can hold 22km3 of flood water. It is the largest HEP station in the world, with 26 turbines. Locks have been built so ships can pass through. 3600km of levees
- 36Positive Effect of the Three Gorges DamMajor flooding has been reduced from 10 to 100 years. Turbines supply 3% of China's energy demand. Shipping has increased as it is now safer
- 37Negative Effects of the Three Gorges DamPeople had to relocate-2 million in total and 13 cities submerged. Flood 650 factories. Dam will trap sediment leading to failure of the dam causing flooding. Destroy habitats (e.g. siberian crane). Reservoir increase flooding along the tributaries, e.g. the Daining River
- 38Problems of the Levees1998 floods, many levees broke, which contributed to devastating flooding. Many levees were then reinforced and more effective in the 2002 floods
- 39Background Soft Engineering in Abingdon1,500 properties have a 1% chance of flooding every year. Abington has regular floods. July 2007- flash floods. Hard engineering rejected as too expensive and would increase flood risk downstream
- 40Soft Engineering put in placeGravel soakaways have been built along the A34 road. Low value land is allowed to flood. Planning restrictions on Ock floodplain. Tesco revise extension plans. EA has a 24 hour warning. Volunteer flood wardens. Improvements made to riparian buffers along smaller rivers. Planting trees.
- 41Outcomes of the soft engineeringSevere flood warning issued in 2008. Ock floodplain not flooded, but Thames floodplain was, no damage due to floodplain zoning. 2008 floods did less damage than in previous years, with minimal cost, and only a few injuries. Flooding does still happen.
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- AS - Level Geography Fichas sobre River Case Studies, creado por Rosie Carver el 26/03/2016.
- Creado por
- Rosie Carver
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