Бангладештің су тасқындары: себептері мен салдары

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Bangladesh, being situated on the Brahmaputra River Delta (also known as the Ganges Delta) is a land of many rivers, and as a result is very prone to flooding. Due to being part of such a basin and being less than 5 meters above mean sea level, Bangladesh faces the cumulative effects of floods due to water flashing from nearby hills, the accumulation of the inflow of water from upstream catchments, and locally heavy rainfall enhanced by drainage congestion. Bangladesh faces this problem almost every year. Coastal flooding, combined with the bursting of river banks is common, and severely affects the landscape and society of Bangladesh. 80% of Bangladesh is floodplain, and it has an extensive sea coastline, rendering the nation very much at risk of periodic widespread damage. Whilst more permanent defenses, strengthened with reinforced concrete, are being built, many embankments are composed purely of soil and turf and made by local farmers. Flooding normally occurs during the monsoon season from June to September. The convectional rainfall of the monsoon is added to by relief rainfall caused by the Himalayas. Meltwater from the Himalayas is also a significant input. Each year, on average, (around 21% of the country) is flooded. During severe floods the affected area may exceed two thirds of the country, as was seen in 1998. Only about 20% of streamflow is generated by rainfall within Bangladesh. The other 80% flows in from catchment areas outside the country, overwhelmingly via three main rivers: the Ganges, the Brahmaputra Jamuna and the Meghna. The floods have caused devastation in Bangladesh throughout history, especially in 1951, 1987, 1988 and 1998. The (2007 South Asian floods) also affected a large portion of Bangladesh.

Small scale flooding in Bangladesh is required to sustain the agricultural industry, as sediment deposited by floodwaters fertilises fields. The water is required to grow rice, so natural flooding replaces artificial irrigation, which is time consuming and costly to build. Salt deposited on fields from high rates of evaporation is removed during floods, preventing the land from becoming infertile. The benefits of flooding are clear in El Niño years when the monsoon is interrupted. As El Niño becomes increasingly frequent, and flood events appear to become more extreme, the previously reliable monsoon may be succeeded by years of drought or devastating floods. Despite all of this, floodings also have very positive effects and it is that corn grows on the water, with the floodings corn can grow benefiting agriculture and the economy in the area.

While the issue of flooding and the ongoing efforts to limit its damages are prevalent throughout the entire country, several types of floods have recently occurred regularly, affecting different areas in their own distinct way. These flood types include: and affected of land, (about 40% of the total area of the country) and was estimated as a once in 30 70 year event. The seriously affected regions were on the western side of the Brahmaputra, the area below the confluence of the Ganges and the Brahmaputra and considerable areas north of Khulna. The flood of 1988, which was also of catastrophic consequence, occurred throughout August and September. The waters inundated about of land, (about 60% of the area) and its return period was estimated at 50–100 years. Rainfall together with synchronisation of very high flows of the three major rivers of the country in only three days aggravated the flood. Dhaka, the capital of Bangladesh, was severely affected. The flood lasted 15 to 20 days. In 1998, over 75% of the total area of the country was flooded, including half of Dhaka. The flooding caused contamination of crops and animals and unclean water resulted in cholera and typhoid outbreaks. Few hospitals were functional because of damage from the flooding, and those that were open had too many patients, resulting in everyday injuries becoming fatal due to lack of treatment. 700,000 hectares of crops were destroyed, 400 factories were forced to close, and there was a 20% decrease in economic production. Communication within the country also became difficult. The 1999 floods, although not as serious as the 1998 floods, were still very dangerous and costly. The floods occurred between July and September, causing many deaths, and leaving many people homeless. The extensive damage had to be paid for with foreign assistance. The entire flood lasted approximately 65 days. The 2004 flood was very similar to the 1988 and 1998 floods with two thirds of the country under water. In early October 2005, dozens of villages were inundated when rain caused the rivers of northwestern Bangladesh to burst their banks. The floods that hit Bangladesh in 2007 affected 252 villages in 40 districts causing millions of people became homeless. Floods also occurred in 2015 and 2017.

Year Crop damage (million tons) Total financial loss (million taka) 1953 0.6 1954 0.7 1500 1956 0.5 1580 1962 1.2 1500 1966 1.0 600 1968 1.1 1200 1969 1.0 1100 1970 1.2 1000 1974 1.4 20000 1980 0.4 4000 1984 0.7 4500 1987 1.5 35000 1988 3.2 40000 1998 4.5 142160