World’s Worst Regional River Floods

World’s Worst Regional River Floods

With the lower and middle Mississippi River having approached and, in some locations surpassed, its greatest flood stage on record I thought it timely to compare this spring’s event with those in the past from around the world. Aside from drought-induced famines no weather-related natural disaster has exacted the toll that massive regional floods have on the earth’s population.

Huang He (Yellow) and Yangtze Rivers, China

The deadliest river in the world, the Huang He (Yellow River) of China, has taken the lives of as many as seven million people over the course of the past 150 years. This included the single deadliest flood of all time that occurred in 1931 and drowned between one and four million in China’s Shandong and Henan Provinces (many of these fatalities were also the result of an ensuing famine). The same year the Yangtze River also flooded, killing another 145,000. In 1887, the Huang He caused the deaths of 900,000 to two million during another of the river’s catastrophic flood events.



A riverboat rests high and dry along the shore of the Yangtze River following a flood in the 1930s. The Yangtze has sometimes risen up to 100 feet above its normal stage.

The cause of these floods is silt washed into the river from loess deposits in the river headwaters (see this link for an explanation of loess deposits) that have elevated the river above the surrounding flood plain and so dikes have been built to contain the river’s course, thus when the dikes are overwhelmed the ensuing flood quickly submerges the thousand of square miles of neighboring flood plains. In the past decade the Three Gorges Dam Project has so far been successful in mitigating the river’s flooding.



A dam on the Huang He (Yellow River) releases a massive wall of water in order to flush silt out of the river’s lower reaches. The silt-causing loess deposits are the reason for the river’s eponymous name.

Floods have changed the course of the Huang He many times as this map below illustrates.



Rivers of the Gangetic Plain of India and Bangladesh

Given the Ganges River and its tributaries flood on a regular basis and that this part of the world is prone to mass casualties in the event of a natural disaster, it is interesting that no truly catastrophic flood is on record for the region. The deadliest such flood in modern history was that of September 1988, when an estimated 2,000 - 5,000 died in West Bengal State of India and in Bangladesh following four months of torrential monsoon rains.

The Indus River of Pakistan occasionally floods as well, but never in as spectacular fashion as it did last summer (August 2010) when up to 20 million people were displaced and over 1,500 died.

Rivers of Europe

The most flood-prone River in Europe is the River Arno in Italy. It has produced a catastrophic flood about once every hundred years for the past millennia. The last such was in November 1966 when Florence was inundated and 149 lives were lost. The flood was best known for the terrible destruction wrought to Florence’s cultural heritage including severe damage to the world-famous Uffizi Gallery, the primary art museum of Florence.



The Arno River rages out of control through the city of Florence, Italy during the flood of 1966 Photo by Balthazar Korab.

The deadliest river flood in European history was that of the River Neva when it overflowed its banks in and around St. Petersburg, Russia on November 19, 1824. Over 10,000 were downed. Virtually every dwelling in the city was flooded to the top of its first story including the Winter Palace of the czar and his family.

Africa

The Nile River has flooded virtually every year since time immemorial. Since the flooding is anticipated there has never been a catastrophic (in terms of human casualties) flood along its length. The possible exception to this was in August 1988 when Khartoum, Sudan was flooded destroying a refugee shantytown that had been erected along the banks of the Nile. Over 100 drowned according to press reports.

Mozambique and South Africa have had several devastating river floods in recent years as a result of tropical storms. The worst such was in 2000 when two tropical storms that made landfall between February and April that year unleashed torrents of rain and many rivers went into flood. Over 800 died as a result.



Flooding in Mozambique in 2000 trapped hundreds on this bridge leading to the town of Xai-xai. Photo from AP.

South America

The Amazon River, in spite of its vast size and drainage basin, rarely floods in an unexpected way. This is because its two principle tributaries, the Rio Negro and the Madeira River lie on opposite sides of the equator and experience different rainy seasons, so their contribution to the Amazon flowage tend to cancel one another out. Also, the Amazon has a series of large, shallow lakes along its way that act as a natural flood control mechanism. All of South America’s worst flood disasters have been the result of flash floods in mountainous regions (as happened in Brazil earlier this year and has been on-going in Columbia since last November).

North America

Obviously, the Mississippi River is the most flood-prone river on the continent and second in the world only to the rivers of China. So far (as of this writing), the highest flood stages on record this past week have not yet resulted in catastrophic flood damage or loss of lives. This, of course, is a result of the amazing system of levees and flood-control projects along its length. The last time the river flooded (along with the Missouri River) in a major way was in 1993. The Great Flood of 1993 resulted in $26 billion in damage (in current dollars—actual amount at time was $18 billion) which qualifies this as the costliest river flood in U.S. history.



The Missouri River floods a highway interchange near the Jefferson City, Missouri Airport on July 30, 1993. Photo from the Missouri Highway and Transportation Department.

The flood of 1927, however, killed and displaced far more people than the flood of 1993 even though the crests reached were not as high as those attained in 1993 or now. The death toll from the 1927 flood has variously been reported at between 246 and 313 and that of 1993 at 48. In 1927 some 750,000 were displaced versus 55,000 in 1993.



Flood refugees crowd onto an evacuation barge on the Sunflower River in western Mississippi during the 1927 flood. Photo from Library of Congress.

Deadliest Regional River Flood in U.S. History
The deadliest regional river flood in U.S. history was that of the Ohio River in March 1913. Four days of torrential rain (up to 11.16” in Bellefontaine) sent most of Ohio’s rivers into flood. The Miami River in Dayton crested some 34 feet above flood stage inundating the city and killing 123. All told 467 lives were lost in the region.




A map and table produced by USGS illustrate the rivers of risk in the United States and some of the historical floods of the 20th century.

Noah’s Flood

Obviously, great river floods have occurred in times prior to the modern records I list above. The historical event of the so-called ‘biblical flood of Noah’ has its basis in fact. Archeological evidence shows that at some time around 2400 BC the Tigris-Euphrates Valley was entirely submerged and silt some 10 feet deep was deposited in a very short amount of time.