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The Management of Rivers in Developed Countries to Prevent Flooding.

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Introduction

The Management of Rivers in Developed Countries to Prevent Flooding As the world has become more developed in certain countries, settlements have always been drawn to rivers. The supply of water is necessary for consumption, industry and transportation and therefore major cities have grown up around rivers e.g. The Thames-London, The Mississippi-New Orleans, Memphis etc. A natural thing for a river to do is to flood and with the impermeable materials laid down in cities, flood risks increase. The risk of flood is dangerous in cities where population density is high and more people would be effected, so this flood risk is always trying to be reduced. The Mississippi in North America is 3000km long and has a drainage basin three times as big as the whole of the British Isles. This massive river was always going to attract settlement and did as large cities have sprouted up along its course e.g. Memphis, New Orleans, St. Louis etc. One of the ways that early settlers used to reduce flood risk and work the river to their advantage was to build Wind Dykes and Levees. ...read more.

Middle

The village of Lynmouth was small and quite but they had straightened their river so tourist accommodation could be built, as the meanders were inconvenient. In the first fortnight of August 1952 it was exceptionally wet throughout the Southwest of England leaving the ground saturated in Exmoor. On the 15th of August there was a huge amount of rainfall and the two main tributaries of the Lyn flooded. When this got to the village of Lynmouth the river was carrying so much discharge and was travelling so fast that it reverted to its old route causing catastrophic effects. This was because its old course ran straight through the village (the discharge was also carrying large boulders), this ruined homes and claimed about 20 lives. So perhaps straightening rivers is not always the right way to reduce flood risk. The Lyn since then has been allowed to flow in its natural course and there hasn't been a major flood there since. All these methods so far are examples of hard engineering but a popular form of soft engineering used on the Mississippi is Afforestation. ...read more.

Conclusion

It also stops the river water mixing with the salt sea water and so the water is fresher. A method that has been used in Exeter on the river Exe and on the Mississippi was building diversionary spillways. These are channels next to the river that can take flood water when it overflows. The Bonnet Carre spillway begins 50km north of New Orleans and ends in the Gulf of Mexico. This spillway has greatly reduced the flood risks at New Orleans and Baton Rouge. The spillway on the Exe River has also been effective in stopping the overflow of floodwater spilling into the town of Exeter. Other methods of trying to reduce flood risk are mainly soft engineering. Another tactic used is dredging and is very effective this is where the sediment at the bottom of the river is constantly scooped out to maintain a deep water channel. This means more discharge can be held so in times of flood more water can be held in the river channel. Practising evacuations and having prepared emergency services is always a good precaution to have ready in case the river does actually flood. The methods mentioned in this paragraph have both been used of the management of the Tees. ...read more.

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