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Bangladesh, 1974
Bangladesh is a riverine country where recurrent flooding is both common and necessary. Every year large areas are submerged during the monsoon season and fertilized by deposits of fresh alluvium, i.e., the soil deposited by moving water. However, if the waters remain stagnant for too long, these beneficial floods become major disasters. Such was the case in the summer and fall of 1974 when flooding extended over nearly one-half of the country and stagnated for more than a month. At least 1,200 people died in the floods and another 27,500 died from subsequent disease and starvation. Approximately 425,000 houses were destroyed or severely damaged and the losses to agriculture were estimated at U.S. $325.9 million. A total of 36 million people suffered severe hardship and losses due to the disaster.
The devastation of the floods can be attributed to more than just a malicious act of nature. Neglect and lack of administrative control were also contributing factors.2 Under colonial rule regular dredging had helped to maintain adequate river depth. After independence, however, protective measures were lax and silting of rivers and deforestation resulted in gradually increasing flood levels. Slow environmental degradation left Bangladesh virtually defenseless against destructive flooding.
The most devastating effect of the floods was on the agricultural sector. Although agriculture accounts for 60 percent of the Gross Domestic Product (GDP) and employs 80 percent of the population, Bangladesh has not been able to feed itself. Ninety percent of the flooded 1.6 million hectare (four million acres) was rice lands, the country's major crop. Little of this could be recuperated since the replanting season had already passed.
Supply problems were compounded by the lack of a buffer stock, absence of foreign exchange to purchase food, and failure of food aid shipments to arrive in time. The longstanding foodgrain gap increased from 1973-74 to 1974-75. As a result, many people who escaped drowning died of starvation.
The country was already in the midst of a serious payments crisis when the floods increased the problem. A reduction in export revenue from the Bangladesh jute crop coincided with massive import requirements for food assistance after the disaster. The result was a severe trade imbalance and an increase in the current account deficit by U.S. $250 million.
Per capita income and income distribution also suffered during this period. The countryside became increasingly impoverished as many small landholders lost both their crops and land. The decline in agricultural output led to higher levels of unemployment and underemployment. Masses of destitute rural people migrated to urban areas where job opportunities proved equally scarce. Added to this was a 50 percent inflation rate fueled by escalating prices of essential commodities now in short supply. In sum, the flood directly caused deterioration in levels of output and combined with rising unemployment and inflation to disturb the once moderately equitable nature of Bangladesh society.
Yellow River, China
China's Yellow River has the dubious distinction of being responsible for more human deaths than any other individual feature of the world's surface. The cause for this is the river's unique form and configuration. For nearly 4,000 kilometers (2,500 miles) it flows through the mountains and plateaus of northern China, and on its route through the easily eroded loose soils it picks up an enormous quantity of silt. The flow of the river may be 40 percent yellow silt (which gives it its name) when it arrives at Kaifeng. From there it travels another 800 kilometers (500 miles) to the sea across the great Yellow Plain--essentially a massive alluvial fan, sloping more steeply than a true delta--which is also 800 kilometers wide and spreads around both sides of the mountains of Shantung. The river gradient across the plain is far higher than in a normal delta, but the Hwang Ho, as the Yellow River is known in Chinese, is still unable to carry its sediment load, and the plain is made of redeposited silt.
From Kaifeng, 15 channels radiate across the plain. Each time the Yellow River tops one of these, it causes enormous floods before resuming a single channel. The floods have drowned unbelievable numbers of people on the crowded plain, and the destruction of crops results in famine and yet more deaths. In only three floods since 1887 the Yellow River has killed over 6,000,000 people.
The levees, which were started over 2,500 years ago, have had to be constantly raised by the labour-intensive methods for which the Chinese are famous. There is nothing with which to build them except the silt. The constant raising means that the Yellow River now crosses its plain about 7.5 meters (25 feet) above the surrounding countryside, between inner and outer levees that form a belt 19 kilometers (12 miles) wide. The silt is the cause of the problem, for it is constantly deposited in the river channel. The river rises to yet higher levels and the Chinese are left with a literally never-ending task of building the levees higher still. Because of this the Yellow River now has no tributaries for over 640 kilometers (400 miles), and millions of people live below river level with the constant threat of flooding. There are no hills in the plain, no escape routes in the event of a flood. And the average area flooded each year is 8,200 square kilometers (3,000 square miles). Because the plain is below river level, it cannot drain. Regions stay flooded to the horizon for a year at a time. Once a major levee break lets the river completely escape, it occupies a braided course perhaps 24 kilometers (15 miles) wide for up to 10 years before it settles itself into a new channel
Comments
These notes are aimed at students studying for Edexcel (B) Unit 5 - Hazards, though will be suitable also for people studying with different exam boards and at different levels.
They were originally submitted by wackojacko in this thread on TSR Forums.
