A large concrete wall built across a river, and it controls flooding by limiting the amount of water that goes through it. A reservoir builds up behind it. ( a state of water)
Advantages:Reduces flooding, hydroelectric power, water levels controlled, renewable energy, allows more transport to pass, new habitat, make new jobs.
Disadvantages: very expensive, long time to build, reservoir could flood, a mass of area flooded, people moved, destroys habitats, can extinct animals, dams can break, needs management.
Causes: Heavy prolonged rainfall, sea levels were at high tide, gale force winds, tidal surge.
Impacts: Exceptionally high waves,a round 220 properties have been flooded, transport network disrupted with roads and trains delayed or cancelled, evacuation in Dorset, widespread flooding, power cuts, highest tide on the welsh coast since 1997.
Management: spend more money on equipment, higher investment level in flood defenses.
Location: Bangladesh is in between India, Myanmar, and China. It is above the Bay of Bengal. It is located in Asia. It is found near the Himalayas and it has the river ganges running through. The main cities are Dhaka, Khulna, and Chittagang. River meghna and River Jamuna.
Population: 150 million
Physical causes of floods: monsoons, Bangladesh is mostly a huge flood plain, 70% is less than 1m above sea level. Rivers, lakes, swamps cover 10% of land, tropical cyclones bring heavy rain and storm waves, snow melts in summer and floods river Ganges.
Immediate effects: floods covered more than half of Bangladesh, 760 people were killed, 6.5 million people were left homeless, more than 35 million people were affected. Rice growing and fish faming were disrupted, roads and bridges were damaged and destroyed.
Later effects: More than 1 million children suffered from malnutrition from disease in the following months, government rebuilding costs for roads and industry were estimated at US $2-3 billion, emergency food aid was needed until the following years harvest.
Short-term responses: the prime concern is for the health, survival ad suffering of the people affected, emergency aid provides food, drinking water, medicine, elastic sheets, boats for rescuing people and animals from international organisations governments in rich countries and charities, distribute water purification tablets and provide help with repairing houses and restarting economic activities such as farming and fishing.
Long term responses: World bank prepared an action plan for flood control. The plan involved the completion of 3500 kilometers of coastal and river embankments and included seven large dams partly to stop water from reaching the land and partly to provide up to 15 flood water storage basins. This is an example of the 'hard engineering approach' to flood management. Millions of dollar spent but the scheme remains unfinished due to a mixture of corruption and inadequate funding. Suggestions have been made that Bangladesh just really need warning schemes and flood forecasting, flood shelters stocked with emergency supplies. These strategies are less likely to damage delicate ecosystems thereby making a contribution to sustainable development.
Location: The three gorges dam is situated in China. It spans the Yangtze river by the town of Sandouping, located in Yilling District, Yichang, Hubel province.
Facts:the dam is built in a steep valley. The dam wall is huge:2309 m long, 101 m high and 115 m thick at the base.The water spins turbines in the dam wall creating electricity. Ships can climb up and down beside the dam using a system of locks. A massive lift is also being built, to raise and lower large ships. The dam is generating electricity. It provides over 2% of the electricity China needs. In terms of electricity it generates its the worlds largest power station.
Advantages: The electricity will benefit many thousands of factories, other businesses and homes. Thanks to the deep reservoir behind the dam large ships can now go further up the Yangtze to bring cargo. Industry can now go to towns along the river. Hydroelectricity is clean energy as no fuels are burnt and nor emissions are produced. The dam controls the flow of water so it is hoped that future floods can be prevented. The power generated by the 34 generators is enormous.
Disadvantages:The dam costs about £27 billion. The fish and other organisms are stopped from moving freely. The increase in shipping affects them too. Now the Yangtze dolphin has nearly died out. The poisonous levels of sewage and factory pollution will build up in the reservoir. This would harm wildlife and humans. At drier times of the year, downstream of the dam the river level is falling really low. Around 1.25 million people were moved to make way for the three Gorges reservoir. They left 2 empty cities, 116 towns, and hundreds of villages. These were drowned forever. So were farms, family graves, and historic sites. Not enough money was given as compensation. The area is prone to earthquakes and the weight of the water in the reservoir puts extra strain on the surrounding rock. Filling the reservoir has already caused many small earthquakes, and landslides near the river.