Floods may occur when a dam breaks.
Geological evidence suggests that mammoth floods occurred in the past, and no data is available for some relatively recent floods that have occurred in remote areas of the globe. However, since the mid-eighteenth century, increasingly reliable data gives us an insight into some of the world’s biggest floods.
Indus River Flood
In 1841, an earthquake rocked an area currently in Pakistan. The quake caused an avalanche on the slopes of a lofty peak called Nanga Parbat, and tons of earth and rock plunged into the Indus River, temporarily blocking the flow of its waters. Eventually this landslide dam gave way, and the accumulated waters burst forth. The banks of the Indus could not contain the immense volume of water that suddenly descended, and one of the greatest floods in history occurred with considerable loss of lives and property. According to the U.S. Geological Survey, 540,000 cubic meters of water rushed downstream every second when the dam broke.
Yellow River Floods
The Huang Ho or Yellow River is China’s Sorrow. It has often been the scene of devastating floods. In the fourteenth century, Huang Ho floods upset the peasants, who blamed the emperor, who was theoretically a god. The resultant unrest contributed to the fall of the Yuan dynasty. One of the greatest of these recurring Yellow River floods took place in 1931. Death toll estimates ranged from 1,000,000 to 3,700,000, according to Epic Disasters. Other significant Yellow River floods took place in 1887 and 1938, according to the same source. The latter was a man-made flood designed to gain an advantage in war.
Rain-Induced Amazon Flood
Rainfall has caused some of the world’s biggest floods. During the rainy season, the Amazon River regularly overflows its banks and deposits water in a floodplain. However, in 1963 and again in 1976, extra heavy rains resulted in an abnormal overflow in the area of Obidos, Brazil, and an even bigger flood occurred in the same area in 1953. According to data published by the U.S. Geological Survey, the 1953 flood is the biggest meteorological flood on record.
The Katla volcano in Iceland lies under a massive glacier called Mýrdalsjokull. Its 1918 eruption caused glacial ice to melt, and a great volume of water flowed down the mountainside, causing a flood. Katla eruptions caused another memorable flood in 1311 and an especially severe inundation in the eighteenth century.
Indian Ocean Tsunami
On December 26, 2004, an earthquake generated a tsunami that temporarily inundated the coastal areas of many countries in and around the Indian Ocean. The earthquake’s center lay west of Sumatra, and Indonesia suffered most, but damage occurred in such far off places as Madagascar and South Africa. This tsunami caused far more casualties than the tsunami caused by the eruption of Krakatoa in 1883.
Even such superpowers as the United States and Russia occasionally succumb to the greater power of a large flood. In the United States, great floods occurred when the Mississippi River overflowed its banks in 1927 and again in 1993. In Russia, ice temporarily blocked the course of the Lena River in 1967. When the water finally burst through the ice barrier, the Lena overflowed its banks. Melting snow compounded the problem. Lesser floods frequently occur along Russian rivers in spring.