What is a flash flood?
AnswerA flood that rises very quickly, often after intense rain
Flash floods develop within minutes or hours, often when heavy rain falls on steep or hard ground.
Nature · Facts & stats
Flood facts & stats
8 fact-checked facts about floods, each with the reason behind it. 4 more are in today's round and join this page after it closes.
The basics
What is a floodplain?
AnswerFlat land beside a river that floods when the river overflows
Floodplains are built from sediment dropped by rivers when they spill over their banks.
Going deeper
What is a storm surge?
AnswerA rise in sea level pushed ashore by a storm's winds and low pressure
Strong onshore winds and low air pressure pile seawater against the coast during storms.
What does a '100-year flood' mean?
AnswerA flood with a 1% chance of happening in any given year
The term describes probability: such a flood can happen in back-to-back years.
Which huge Dutch flood-defence system was built after the North Sea flood of 1953?
AnswerThe Delta Works
The Delta Works, a network of dams, sluices and storm barriers, was built after the 1953 disaster.
What is the Dutch word for low-lying land reclaimed from water and protected by dikes?
AnswerPolder
Polders are drained areas kept dry by dikes and pumps, once powered by windmills.
Expert level
Which dam, built in the 1960s, ended the Nile's annual flood in Egypt?
AnswerThe Aswan High Dam
The Aswan High Dam holds back Lake Nasser and controls the Nile's flow.
What is a hydrograph?
AnswerA graph showing river flow or level over time
Hydrographs show how quickly a river rises and falls after rain.
Know these cold?Today's round is five questions like these, 20 seconds each. Your streak and level follow you to every arena.Play today's round