Geography - Case Studies

Consequences

1. River level rose by over 2.5m.
2. Bridges were washed away, some were over 100 years old.
3. PC Barker lost his life whilst on a bridge preventing cars to cross.
4. Caused 9km detours - this affected the local buisness.
5. 1200 people had no electricity. 
6. 200+ people were rescued (50 by RAF helicopters)
7. 20 schools closed and they sheltered people.
8. 100s of local buisnesses flooded.
9. Train lines were closed.
10. Prince of Wales visited Cockermouth.
11. Cost of flood damage exceeded £1 million. 
12. Tescos built a temporary shop to accomodate the local area. 
13. Some people looted abandones homes and buinesses. 

Natural Reasons

1. 31.6 of rainfall in 24 hours - ground was already saturated. 
2. Steep releif and thin soils made the interception minimal.
3. Impermeable Borrowdale volcanic rock meant the excess water run straight off.
4. High rates of surface run-off, and combined effect of discharge increasing.

Human Reasons 

1. The sitting and expansion of Cockermouth - at a confluence and saturating flood plain. 

Managment Issues and Strategies

1. Changes to hydrology upstream of dams.
2. Increased evaporation rates becasue reservior has a larger surface area than rivers. 
3. Increase the amount of surface store.
4. Reduction in the velocity of the river upstream. The river is effectivley flowing into stationary water.
5. Increases sedementation can lower the depth of the river and the reservior. This reduces velocity and may also reduce storage capacity. 

Information

• The worlds largerst hydro-electric power dam, is located on the Yangtze River in central China.
• The yangtze is over 600km long and discharges 700+ cubic metres of water annually.
• Its source is in the Himalayas and is the 3rd lonhest river in the world.
• Yangtze is prone to flooding. The last big flood was in 1998 - an area the size of NZ was flooded. All together they have cost $30 billion USD and 30000+ people have been killed in the 20th Centuary.
• 3GD is over skm wide, 100 m think and 100m high.
• The dam has 26 turbines and generates up to 18000 MegaWatta annually. 

Advantages

• China can reduce its dependancy on oil. It greatly suffers from air pollution.
• This will decrease Chinas dependancy on coal and reduce the GHG emissions.
• Creates a sense of national pride. The 3GD produces 50% more power than the next biggest HEP dam.
• The HEP generated will provide 15% of China's energy demand.
• It protects over 10 million people downstream from the risk of flooding. 
• Improved navigation for boats. They can now get to Chongquing.
• Construction, running & maintaining has created 1000s of jobs & increased skill levels.
• Becomea tourist destination and the reservoir has provided leisure oppurtunities. 

Disadvantages

• Dam causes sedementation behind & stops alluvium reaching the flood plains.
• Extinction of the Yangtze River Dolphin.
• The area is seismically active so there is a risk of dam failure & loss of lives if there is an earthquake.
• The reduced discharge & veloctiy of the Yangtze may casue greater deposition at its mouth creating a delta and hampering navigation.
• The flooding casued by the reservior forced 1.3 million+ people to be relocated and submerged 632sq km of land.
• Much fertile land was lost under the reservoir,people relocated but to less fertile areas.
• Cost $70 billion USD to build.
• Many acheological treasures were destroyed. Zhang fei Temple.

When?

18th & 19the November 2009

Where?

Cockermouth in the Lake District.

On the confluence of the River Cocker and the River Derwent.

• Dams e.g. 3GD, Aswan Dam (Ethiopia)
• Striaghtening - Meanders are removed from a river so the water has less distance to travel, it can be removed faster. However it increases erosion and flooding downstream.
• Diversion spill ways - floods are directed away from houseing and settlements into extra land or channels. However in urban areas this isn't possible. e.g. Jingjang Flood Diversion Scheme.
• Flood walls - Cockermouth self reasing barrier.
• Building up levees - the levees are widened and heightened to increase the amount of water a river csn hold before it floods. 

• Aforestation - planting trees which soak up water, incresase interception, less surface run-off and reduces flood risk.
• Flood Farmland - flood farmland before waters get near the city, and homes and buisnesses. Farmland is less costly to repair than houses and industry.
• Wetland Restoration - resorting wetlands to allow them to reliove flooding e.g. Dongting Wetland.

• Aforestation - planting trees which soak up water, incresase interception, less surface run-off and reduces flood risk.
• Flood Farmland - flood farmland before waters get near the city, and homes and buisnesses. Farmland is less costly to repair than houses and industry.
• Wetland Restoration - resorting wetlands to allow them to reliove flooding e.g. Dongting Wetland.

Artesian Basin 

A well that does not require a pump to bring the water to the surface.  There is enough pressure to force the water to the surface without any assistance. The aquifer absorbs and stores water, and in an artesian well, the porus stone is sandwiched between a bottom and top layer of impearmeable rock e.g. shale or clay. 

When an artesian basin is drilled the pressure is relived and the water is able to get to the surface. 

Natural Recharge

Naturally refilling of the aquifer through groundwater flowing through the unsaturated layer. It is very slow. 

4 Major Impacts 

1. Seawater Intrusion - Italy, Turkey, Spain - Tourist accomodation is the main reason for extraction.
2. Subsidence - Water gets sucked from deep below urban areas which casues buildings to sink e.g. Mexico City buildings have sunk 2 metres in some places. 
3. Pollution due to concentration - Occurs in the Granges Plain in Northern India and Banladesh. Arsenic effetcs 25% of wells.
4. Impacts on riverflows- Sinking water tables make rivers less reliable. 

Wetlands

Areas of marsh, fen, peatland or water, whether natural or artificial, permanant or temporary, with water that is static or flowing, fresh, brackish or salt. 

Wetlands purify watrer, they act as a water supply, a flood control, and provide protection to areas with high biodiversity, complex ecosystems and foodchains. 

They also provide commercial benefits and are great transport systems.

Strategies adopted to meet demands for water.

1. Groundwater extraction. Florida.
2. Flood control - maintain key canals, dykes, channelisation. 
3. Tourism.
4. Environmental conservation e.g. Central Everglades Restoration project.
5. Aquifer storage and recovery.
6. Reusing - Using treated waste water e.g. orange county.
7. Reusing recycled water.
8. Desalinaion.
9. WaterSIP - water savings incentive program. 

Brahmaputra River

• Tensions rise as India accuse China of diverting parts of the river.
• China plan to build lots of HEP dams along the river, the biggest being at the 'Great Bend' - going to produce a 10th of te countries demands.
• If successful the dam will divert 200 billion cubic metres of water annually. 60% of the double annual flow! 
• Possible outcome - Will lead to compromise between teh two countries due to the heat of nuclear warfare.