CASE STUDIES

Boscastle floods, Cornwall, August 2004

South-west england had heavy down pours due to an intersive low-preasure systeme that encouraged the uplift of warm, moist air.
200mm of rain fell in 24 hours, particularly intensive between 3 p.m and 4p.m
The weather system appeared to stall over the hills above the castle. Rainfall was heaviest to the east of Boscastle on the high ground
The ground was already saturated, due to previous wet weather, so infiltration of into the ground was limited.
The village lies in a deep valley just downstream of the confluence of the rivers Valency and Jordan
60 properties were submerged under floodwater. Around 70-80 cars were swept away and 100 people airlifted to safety.
There was damage to property, roads, bridges and services
NO LOSS OF LIFE

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The jet stream took a southern track. This meant that the usual anticyclonic weather conditions influenced by the high preasure cell in the Azores did not materialise.
In 2007 heavyiest rain on record. on the 20th of July outstanding storm totals were reported across much of southern Britain, 145mm in Worcestershire.
Flood risks in the summer is normally reduced by dry soil conditions. However, in this case because of the early rain the soil was already saturated, so groundwater was higher due to little infiltration.
Flash floods due to intense storms
Emergency services were widerly deployed to rescue stranded people and to organise evacuations. Tronsport were severly disrupted, with thoursand of motorist stranded. There was also extensice damage to crops
3 people died, 350,000 homes no running water, 140,000 were still affected a week later.
The economic costs; £25 million damage to roads, farmers in the area lost 50% of their crop, £3 billion in flood damage insurance, £1 billion cost to the water industry

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Bangladesh is a low lying country with most of it lying oon a delta land of 3 major rivers,(the ganges, brahmaputra and meghna). The source of this river comes from the Himalayas, so snowmelts and adds dischagre.
It has a monsoon climate, where it has wet seasons between may and september, then low lying pressure and winds blowing from south-west bring heavy rain to coastal regions.
Cyclones bring intense wind and precipitation
Human factors; Urbanisation, rapid deforestation effects the rate of interception and evapotranspiration.
River management is hard as it is a LEDC, this is due to most of the population being subsustence agriculture farmers, so relies heavily of foreign aid to finance large scale projects to provent floods.
Embankments have been built along the river channels in some places, these are designed to increase river capasity, but at the same times have prevented flood water draining back into the rivers.

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In August 2004, 38% of the total land was flooded, including 800,000 hectares of farmland. 36 million people were made homeless. The death toll had risen to 800, many people died as a result of disease and no clean water. There was huge damage to the countries infractructure, including roads, bridges, embankments, railway lines and irrigation systemes. The value of the damage was $2.2 billion.
The goverment work with non goverment organisations providing emergency relief, like food,clothes,medicine and blanket. A disater management team was made by the UN, they supply critical emergency supplies and conducted a damage and need assessment. Self help schemes were made to help local people rebuild.
Flood shelters and early-warning systems hace been put in place. Aloan from the world bank allowed Bangladesh to rebuild.

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3 gorges dam, is the largest hard engineering project. It is located on the Yangtze river in China. This river has a long history of flooding. The dam is a hydroelectric dam designed to power central and east China.
The dam will reduce the rish of flooding for 15 million people and improve nanigation of the river. A huge reservoir, 660 km long by 1km wide. Costing £25 billion
The reservoir has forced the resettlement of 1.2 million people. Resettlement runs along the Yangtze river and most people have been located as near as possible to their former homes.
Monuments have been lost like the Zhang Fei temple.
There has been an increase in erosion further down stream due to the dam.
Sediment will accumulate behind the dam and will need dredging.
Afforestation is needed on the slopes in the drainage basin to reduce the amount of sediment washed into the river and reservoir behind the dam.
There will be negative effects on the environment such as; increase chance of landslides in the area and major disruption to habitats.

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As a result of increased flood risk due to continued urban development in Lewisham and Greenwich, more needed to be done to protect the area from flooding.
The solution was proposed by local residents, who formed the quaggy waterways action group (QWAG) to campaign for a more sustainable approch.
The plan was to bring the river back above ground once again, cutting new channel for it through Sutcliff Park, creating a multi-functional open space.
Although a culvert remained to take some water underground during flooding conditions, a new lake was created to take over when it became full.
The park itself was lowered and shaped to create a floodplain where water could collect naturally instead of rushing downstream through arificial channels to flood Lewisham town centre.
The flood storage caoacity is 85,00 m and has protected 600 homes and businesses
A wetland has developed with reedbeds, meadows and trees.

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