49 Fun Facts About Floods

Flash floods have a gap between rainfall and flooding of fewer than how many hours?

Six hours: the US National Weather Service defines a flash flood as one beginning within six hours of the causative rain; paved urban ground that cannot absorb water produces them often.

Which adjective describes flooding from rain pooling on saturated or frozen ground, not a river overflowing?

Areal flooding: on flat ground such as floodplains and endorheic basins, rain arrives faster than saturated or frozen soil can absorb it or the land can drain it, so water pools in place.

A '100-year flood' is one with what probability of occurring in any given year?

A 100-year flood has a 1% chance of being equalled or exceeded in any given year; the name misleads, since many places can each see their own 100-year flood in the same year.

Deliberate agricultural flooding is used to prepare fields for growing which semi-aquatic crop?

Rice is grown in paddy fields that are flooded on purpose; land is also flooded deliberately for military defence or for river management.

Which of these is a waterborne disease whose spread increases after floods?

Cholera spreads through water contaminated with sewage, so outbreaks follow floods; hepatitis A and typhoid are other waterborne risks, while malaria rises via mosquitoes breeding in standing water.

Periodic flooding sustained ancient peoples along the Tigris, Euphrates, Indus and which other river?

The Nile's annual inundation deposited fertile silt on Egyptian fields each summer; Mesopotamia on the Tigris and Euphrates and the Indus cities depended on the same seasonal cycle.

'Overland flooding' in the flat Red River Valley affects Minnesota, North Dakota and which Canadian province?

Manitoba: the Red River of the North flows north past Winnipeg into Lake Winnipeg, so spring melt upstream in the Dakotas meets river ice not yet thawed downstream and spreads across the flat valley.

A 1963 landslide into which Italian dam's reservoir sent a wave that killed about 2,000?

The Vajont Dam in the Dolomites survived intact, but on 9 October 1963 a landslide of some 260 million cubic metres into its reservoir sent a wave over the crest that destroyed Longarone and killed about 2,000 people.

The 1931 floods hit which two major cities on the Yangtze?

Wuhan and Nanjing, then the capital, were both inundated in summer 1931; the government estimated 25 million people were affected, and four Yangtze stations recorded over 600 mm of rain in a single month.

Which waterway, nicknamed 'China's Sorrow', flooded in 1887, killing at least 930,000?

The Yellow River burst its dikes near Zhengzhou in Henan in late September 1887 after days of heavy rain; death estimates run from 930,000 to about two million.

The Great Mississippi Flood of 1927 inundated roughly how many square miles?

The 1927 flood inundated about 27,000 square miles of the lower Mississippi valley, with water up to 30 feet deep standing for months; Arkansas, Mississippi and Louisiana bore most of the damage.

Whose handling of the 1927 Mississippi flood as commerce secretary helped propel him to the presidency?

Herbert Hoover, then commerce secretary, ran the relief effort and rode the publicity to the presidency in 1928; the disaster also helped elect Huey Long governor of Louisiana.

The Johnstown Flood of 1889 was caused by the failure of which dam upstream of the Pennsylvania town?

The South Fork Dam, about 14 miles upstream, gave way on 31 May 1889 after heavy rain, releasing a private resort lake owned by a club of Pittsburgh millionaires.

How many people did the Johnstown Flood kill?

2,208 people died (some counts say 2,209); for a while the torrent equalled the average flow of the Mississippi, and Clara Barton's Red Cross mounted its first major disaster relief there.

Which Pittsburgh industrialist led the group that made the Johnstown reservoir a private resort?

Henry Clay Frick led the Pittsburgh speculators who bought the reservoir in 1879 and turned it into a fishing and hunting club; members were widely blamed, but none was held legally liable.

The Great Molasses Flood of January 1919 struck which American city?

Boston: a tank holding 2.3 million gallons burst in the North End on 15 January 1919; locals claimed the area smelled of molasses on hot days for decades.

Roughly how fast did the wave of molasses travel through the streets in 1919?

The wave moved at about 35 mph (56 km/h) and stood some 25 feet high; it killed 21 people and injured about 150, and the tank belonged to the Purity Distilling Company.

The North Sea flood of 1953 was caused by what?

A heavy storm surge, driven by a severe northerly windstorm over the North Sea, struck the Netherlands, Belgium and eastern England on the night of 31 January to 1 February 1953.

How many people died in the Netherlands in the 1953 flood, most of them in the province of Zeeland?

1,836 people died in the Netherlands, most of them in Zeeland's island polders; the Dutch call it simply the Watersnoodramp, the Flood Disaster.

The 1953 flood killed 58 people at which low-lying spot in the Thames estuary in Essex?

Canvey Island, off the Essex coast, was inundated with the loss of 58 lives; the car ferry Princess Victoria also sank in the same storm in the North Channel.

Which system of dams and storm-surge barriers did the Netherlands build after the 1953 flood?

The Delta Works, built from 1954 to 1997, shortened the coastline by closing off the estuaries of Zeeland and South Holland with a chain of dams, sluices and storm-surge barriers.

The final piece of the Dutch post-1953 defences, completed in 1997, was which storm-surge barrier?

The Maeslantkering, two huge swinging gates on the Nieuwe Waterweg near Rotterdam, was completed in 1997 as the final element of the post-1953 defences; gates were chosen over a dam so the port could stay open.

In which year was the Afsluitdijk, which turned the Zuiderzee into the IJsselmeer, closed?

The Afsluitdijk was closed on 28 May 1932 after five years of construction and opened to traffic in 1933; the engineer Cornelis Lely gave his name to Lelystad, built on reclaimed land.

The Thames Barrier, protecting London from storm surges, has been operational since which year?

The Thames Barrier became operational in 1982 and was formally opened by the Queen in May 1984; its rising sector gates were Charles Draper's idea, and it stands at Woolwich.

The deadly Lynmouth Flood of August 1952 followed a night of extreme rain on which upland?

Exmoor received about 229 mm of rain in 24 hours on 15 August 1952 on already saturated ground, sending the East and West Lyn rivers through Lynmouth and killing 34 people.

The Great Flood of 1993 in the American Midwest ran along the Mississippi and which other great river?

The Missouri and the upper Mississippi both flooded from April to October 1993 after months of rain; the crest at St. Louis near their confluence set a record, and in some measures the flood surpassed 1927.

The 2010 monsoon floods along the Indus basin submerged roughly what share of Pakistan's land area?

About one-fifth of Pakistan's land area was under water and some 20 million people were affected; UN Secretary-General Ban Ki-moon called it the worst disaster he had ever seen.

Pakistan's 2022 floods killed 1,739 people and caused about how much damage?

Damage was put at about $40 billion by Pakistan's government; the climate minister said a third of the country was under water, and glacial melt after a heatwave added to record monsoon rain.

Melting glaciers contributed to the 2022 Pakistan floods, causing glacial flooding in which northern region?

Gilgit-Baltistan, home to thousands of Karakoram and Himalayan glaciers, saw glacial lake outburst floods after the 2022 heatwave; one destroyed the Hassanabad bridge in Hunza in May.

In the Atrahasis epic, which god secretly warns his priest of the flood and tells him to build a boat?

Enki, god of fresh water and wisdom, whispers the warning through a reed wall, defying Enlil's plan to drown mankind; the story predates Genesis and shares its structure.

The Greek counterpart of Noah, who survived Zeus's flood with his wife Pyrrha, was called what?

Deucalion, son of Prometheus, and Pyrrha rode out the flood in a chest and repeopled the earth by throwing stones over their shoulders; the Hindu tradition tells of Manu and the great flood.

Deforestation and the removal of which water-absorbing habitat increase flooding?

Wetlands act as sponges, absorbing and slowly releasing water, so draining them raises flood peaks; straightening waterways and building levees also shift and often worsen flood risk downstream.

Climate change raises flood risk via sea-level rise and by intensifying which global process?

The water cycle intensifies because a warmer atmosphere holds about 7% more moisture per degree Celsius, so extreme rain events become more frequent and heavier.

Muddy floods, where run-off picks up sediment, most often occur when overland flow crosses what?

Tilled fields with bare, loose soil shed muddy run-off during heavy rain, carrying sediment onto roads and into villages downslope; the problem is studied especially in Belgium's loess belt.

The word 'flood' can also refer to the inflow of what?

'Flood tide' is the rising tide; tidal flooding in estuaries mixes river and coastal processes.

The study of floods belongs to hydrology and which branch of engineering?

Hydraulic engineering, the branch dealing with the flow and conveyance of water, designs levees, spillways and barriers, though levees can push the problem downstream.

The Arno's November 1966 flood damaged millions of books and artworks in which Italian city?

Florence: the Arno burst its banks on 4 November 1966, leaving several metres of water in the old city and damaging millions of books and artworks; volunteers called 'mud angels' helped the clean-up.

The Thames Barrier is raised at which point of the tidal cycle when a surge threatens?

Low water: the gates are closed after the ebb, roughly four hours before the surge peak, leaving room for the river to flow in; they reopen once the sea level outside has fallen back to the river level.

Which body named the Zuiderzee Works and post-1953 Dutch defences one of the Seven Wonders of the Modern World?

The American Society of Civil Engineers listed the Dutch North Sea Protection Works among its Seven Wonders of the Modern World; the Zuiderzee scheme alone reclaimed about 1,650 square kilometres and created the province of Flevoland.

The 1927 Mississippi flood left more than how many people homeless?

More than 700,000 people were left homeless, many of them Black sharecroppers housed in levee-top refugee camps; the disruption pushed many to leave the South for good in the Great Migration.

The 1931 Yangtze floods followed which climatic sequence?

Drought, then snowmelt and rain: after dry years from 1928 to 1930, heavy winter snow melted into sustained spring rain and summer cyclones, so the usual three high-water seasons merged into one deluge.

What is the US National Weather Service's well-known slogan for flood safety?

'Turn Around, Don't Drown' is the National Weather Service's trademarked flood-safety slogan, urging people to back away from flooded roads rather than cross them, since even shallow moving water can sweep a car away.

What is a Dutch 'overlaat'?

An overlaat is a deliberately lowered levee segment: the Beerse Overlaat on the Meuse let floodwater spill onto land judged less valuable, relieving pressure on the dikes protecting areas downstream.

According to FEMA, roughly what share of small businesses never reopen after a flooding disaster?

FEMA puts it at almost 40 percent of small businesses; the agency also estimates that a wet basement alone can cut a US property's value by 10 to 25 percent.

The online GFMS flood-mapping tool uses rainfall data from which NASA satellite mission?

GPM data is combined with a land-surface model of vegetation, soil and terrain to estimate runoff into streams.

Which river's August 2002 flood inundated Dresden's historic centre?

The Elbe crested at 9.40 metres in Dresden on 17 August 2002, its highest level in more than 150 years, flooding the Zwinger and the Semperoper.

Which 2005 hurricane's floodwaters covered about 80% of New Orleans after its defences failed?

Hurricane Katrina made landfall on 29 August 2005; its waters breached the city's flood defences, covering about 80% of New Orleans, and the failures were later ruled an engineering error.

Typhoon Nina's rain burst which dam in Henan province in August 1975?

The Banqiao Dam on the Ru River collapsed on 8 August 1975 after Typhoon Nina dropped roughly a year's rain in days; estimates of the dead range from 26,000 to over 200,000.

Which event on 26 December 2004 flooded coastlines from Indonesia to East Africa?

A tsunami raised by a magnitude 9.1 earthquake off Sumatra on 26 December 2004 flooded coasts around the Indian Ocean and killed about 230,000 people in 14 countries.