Example of coastal flooding

Bangladesh is a very low lying country, (only 1-2 meters in most parts). The contribution of global warming in the last few years has set in motion the rise in sea water levels, the narrow north tip to the Bay of Bengal, tropical storms that whip up wind speeds of up 225 km/h send waves (up to 8 meters tall) crashing into the coast, the shallow sea bed and the fact that water coming down from the rivers Ganges and Brahmaputra can not escape when the water level rises all contribute to the severe flooding of the Bangladesh coastline.On the night of 29 April 1991 a powerful tropical cyclone struck the Chittagong district of southeastern Bangladesh with winds of around 155 mph. The storm forced a 6 meter (20 foot) storm surge inland over a wide area, killing at least 138,000 people and leaving as many as 10 million homeless.The very large cyclone was “funnelled” down the Bay of Bengal. This was due to a low pressure area – higher sea levels – surge flooding… Snow melt from Himalayas, Deforestation – more water in rivers – more sediment build up – higher risk of flooding , Very heavy rain.Nature + Impact of problem:About 115 million people live in low-lying deltas of the 3 major rivers, The Ganges, Brahmaputra and Meghna. It is predicted that a 1meter relative sea level rise would displace 13 million people more than 1 5th of the countries Monsoon rice land would be flooded. Thousands of areas of biological diversity would be lost to both plants and animals including the larges mangrove forest in the world. The habitats of many species are already threatened by salt water from the Ganges. The large population has caused depletion of all the forests, and farming on slopes has caused much soil erosion.There is not enough land in Bangladesh, especially with the number of people that are farmers, so people take whatever land they can get, including slopes. The soil that is being eroded then reduces the depths of the rivers, making them easily flooded. A thirty foot deep river can become twenty feet deep, and soon ten feet of water is being pushed over the banks of the river. It appears that if the population could be controlled, there would be less and less soil erosion, and therefore the floods could be slowly phased out. And it’s not just one river that is flooding Bangladesh.Reasons why:Bangladesh is located in the deltaic region of three enormous rivers. The rivers are the Ganges, the Brahmaputra, and the Meghna. Global warming is making sea levels rise, causing the land to retain the water for an abnormally long time. Because Bangladesh is getting closer and closer to sea level, because the sea level is rising, the water from the floods is no longer being quickly pulled down towards the ocean. Even if the flood is not that big, the water will remain for a period indefinitely longer than it would without global warming. The causing factors were the large cyclone was “funnelled” down the Bay of Bengal. Due to a low pressure in the area – higher sea levels – surge flooding… Snow melt from Himalayas, Deforestation – more water in rivers – more sediment build up – higher risk of flooding , Very heavy rain.Relative contributions of human factors:Flood control measures in Bangladesh are mainly limited to building of earthen embankments, polders, and drainage some of which sometimes make the problems worse than solve them. A total of 5,695 km of embankments, including 3,433 km in the coastal areas, and 4,310 km of drainage canals have been constructed by the Bangladesh Water Development Board during the last several decades. Embankments have reduced floodplain storage capacity during floods, leading to an increase in water levels and discharges in many rivers. Earthen embankments can easily breach and can be damaged by riverbank erosion. Most of the embankments in Bangladesh have experienced breaching and erosion more than once since their completion. Embankments have created a false sense of security among residents living within embanked areas.What, if anything will change in the future?To change the future of flooding in Bangladesh would rely greatly on outside help as they themselves are unlikely to have the means or funds to ensure their own long term security against flooding the Government of Bangladesh (GOB) has adopted a World Bank sponsored flood action plan (FAP) that calls for the construction of hundreds of kilometres of tall embankments along the great rivers of the Bangladesh delta, enormous drains, and compartments on the flood plains. The feasibility of the FAP has been criticized by numerous researchers on the basis of technical, economical, environmental, socio-political, and ecological grounds.The Dhaka Integrated Flood Protection Embankment cum Eastern Bypass Road Multipurpose Project, which is a component of the FAP, is underway at a calculated initial coast of 24,758.21 million taka. The effectiveness of such embankments as flood control measure is debatable at best. The key in understanding of the long-term factors contributing to increased frequency and duration of floods. Once the causes of the problem are determined, then preventive measures can be taken to reduce future damage caused by floods.

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