Flood Case Study: Bangladesh
The main cause of the floods was unusually severe monsoon rains and an unusually high volume of runoff from melting snow from the snow caps of the Himalayas. These all increased the amount of surface water and the volume of water in Bangladesh two main rivers, which are very large and connect.
The Ganges and the Apparatus both had more than the normal amount of water that they could carry and so were overflowing and flooding. A number of human factors also contributed to the devastating flooding of Bangladesh, including large amounts of deforestation and overbearing.
Deforestation for logging or farming removes trees that would otherwise absorb and delay the flow of rainwater. Overbearing ruins the soil and so water Just goes straight through it and doesn’t soak into the ground for groundwater. This means that the maximum amount of surface water can travel down the hills and tributaries. Bangladesh Itself Is a very poor and highly populated country and cannot afford necessary defense against flooding such as flood banks/walls or rescue services to help survivors and refugees.
Consequences Following the 1998 floods a number of short term flood relief measures were put in lace to try and minimize loss of life – these included: international food aid programmers the distribution of free seed to farmers by the Bangladesh government to try and reduce the impact of food shortages – the government also gave 350,000 tons of cereal to feed people; volunteers / aid workers worked to try and repair flood damage.
In the long term a number of flood prevention measure are possible: the creation of embankments (artificial levees) along the river to increase channel capacity and restrict flood waters – however since 1957, 7,km of flood embankments have been constructed and yet many were breached In the 1998 floods; constructing flood protection shelters (large bulldogs raised above the ground) to shelter both people and animals emergency flood warning systems and plans made for organizing rescue and relief services: providing emergency medical stores in villages building flood proof storage sheds for grain and other food supplies dam construction upstream and major embankments around Dacha have been suggested however lack of money has meant that these suggestions have not been taken further. The floodwater’s swallowed 300,000 houses, 9,700 kilometers (6,027 m’) of road and 2,700 kilometers (1 ,678 m’) of embankment.
Around 1,000 people drowned in the flooding or died from diseases like typhoid and cholera from contaminated water. The flooding dealt a devastating blow to agriculture; 135,000 cattle and 700,000 hectares of crops were lost land. The material destruction was overwhelming: 30 million people lost their homes, 50 square kilometers (19.
3 sq. Ran) of land was destroyed and 1 1,000 kilometers (6,835 ml) of roads damaged or destroyed. Most of the destruction occurred In the Ganges delta. Hood case study Obsolesce M On the 16th, warm air picking up moisture – due to residual heat from the Atlantic sea – traveled towards the South West Cornish coast as prevailing winds.
Upon contact with the topographically vertical coast, these winds experienced a strong up- drafting force thus causing internal moisture to reach the atmosphere, and consequently cool as a string of storm clouds. With convergence and coalescence, enhanced moisture levels resulted in heavy rainfall on the afternoon of 16 August 2004.
185 mm (7 inches) of rain fell over the high ground Just inland of Obsolesce. At he peak of the downpour, at about 1 5:40 GMT, 24. 1 mm of rain (almost one inch) was recorded as falling in Just 15 minutes at Lessened, 2. 5 miles (4 km) up the valley from Obsolesce. In Obsolesce, 89 mm (3. 5 inches) of rain was recorded in 60 minutes.
The rain was much localized: four of the nearest 10 rain gauges, all within a few miles of Obsolesce, showed less than 3 mm of rain that day.
The cause of the very heavy localized rain is thought to be an extreme example of what has become known as the Brown Wily effect. The torrential rain led too 2 m (7 Ft. ) rise in river levels in one our. A 3 m (10 Ft. ) wave, believed to have been triggered by water pooling behind debris caught under a bridge and then being suddenly released as the bridge collapsed, surged down the main road.
Water speed was over 4 m/s (10 MPH), more than enough to cause structural damage. It is estimated that 20,000,000 cubic meters (5. Xx US gal) of water flowed through Obsolesce that day alone. The steep valley sides and the saturated surface ensured a high amount of surface run-off.
Changes in farming practice in the area also possibly contributed, sewage could have been a cause as well, with a reduction of trees and hedges higher up the valley causing water to flow through more quickly than would have been the case in the past. Fortunately, no one died in the flood.
Impact of the flood 75 cars, 5 caravans, 6 buildings and several boats were washed into the sea; approximately 100 homes and businesses were destroyed; trees were uprooted and debris were scattered over a large area. In an operation lasting from mid-afternoon until 2:30 AM, a fleet of 7 helicopters rescued about 150 people clinging to trees and the roofs of buildings and cars. No major injuries or loss of life were reported.
