I'm writing a story in which the characters (and society at large) have to deal with a recurring natural disaster (like hurricane season or the common winter, in a way). What I want to know is how long can I space out the occurrences of this disaster while still having it be a force that shapes the daily lives of the people and culture?

I do have some restrictions. It has to be big enough that it affects daily life: deadly while happening, requiring preparation while not. It can't be so long between events that the natural disaster is doubted. No "legend into myth" type thing. I also don't want variability to be a factor like the winters in ASOIAF. The society isn't supposed to be afraid of sudden disaster just happening or starting out of nowhere.

While I'm at it, what would be a good vector for this disaster? Could a locus migration or animal hibernation happen on the scale of decades? What about a storm or kind of rain that reoccurs on the scale of centuries?

  • $\begingroup$ What technology level are you looking at? Do people have good records of what happened in past generations? Are you willing to allow supernatural events? Magic? $\endgroup$
    – Priska
    Oct 9, 2019 at 2:42
  • $\begingroup$ @Priska Medieval for sure, but maybe with higher levels in the distant past (but that's irrelevant I guess). $\endgroup$ Oct 9, 2019 at 2:47
  • $\begingroup$ Magic? Supernatural events? Different rules of physics? or not? $\endgroup$
    – Priska
    Oct 9, 2019 at 2:48
  • $\begingroup$ No magic and as normal of physics as possible. But I am willing to bend the rules of physics a little if I need to. $\endgroup$ Oct 9, 2019 at 2:50

3 Answers 3


Minimum once a human lifetime

People need to be able to talk to someone who has seen it before for a real feeling for it. Once more than a lifetime, people will forget or water down the effects.

A meteor shower could happen once a lifetime and put the fear of god into them. It would happen at a fixed time so people could tell when the stars are right when it will happen.

  • $\begingroup$ There are some good answers here, but I think this one provides the longest plausible time. Anyone looking for ideas should read the others though! $\endgroup$ Oct 9, 2019 at 19:22

One possible event with a lot of flexibility is to have a flood that happens periodically. Sea levels and river levels rise until they cover all land, or maybe just some land, so that people are forced to flee to higher ground or load themselves into boats and wait out the disaster. After some time, water levels finally recede and people can come back down and resume their lives. Obviously, no preparation would mean certain death, and much of society would have to be built to anticipate this flooding. Castles on high ground might be valued especially.

When the flood recedes, people need a system in place to restore order to society. Goods have to be protected so that they are not stolen by bandits post-flood before the owners get back to them. People who floated away need to find a way to return home.

A quasi-scientific justification isn't hard. You can reduce the phenomenon to tides. Fix an astronomical object, let's call it a blue moon, in a large elliptical orbit. Every X years, this elliptic trajectory aligns with Earth orbit so that the blue moon is very close to Earth and takes up a huge part of the sky. This blue moon exerts an extremely strong gravitational attraction to water for whatever reason; maybe it only attracts water. During the "Time of the Blue Moon", water levels rise to a crazy level and remain that way until the blue moon is gone. The blue moon could easily fit into societal mythology, as a cosmic force of purity, cleansing, etc.

Example: have a flood every 25 years, lasting 6 months. Everybody not fleeing to the mountains will need to find their own boat and stock it with supplies to wait out the flood. Societies will have to store food in advance to prepare. Some societies might even be built around barges designed to float so that they can continue to live and conduct business in Venice-like even during the flood. Military planners will have to take into account the possibility of enemies using the flood to slip past their fortresses and defenses.

  • $\begingroup$ Flooding everything with ocean water is a bad idea due to the salt, which will diminish soil fertility for common edible plants. $\endgroup$
    – Erik
    Oct 9, 2019 at 9:03

There are a lot of possible recurring natural disasters. Like:

  • Hurricanes

  • Tornados

  • Severe winter - Russian buildings are projected with this in mind.

  • Earthquakes - Japanese buildings are projected with this in mind.

  • Tsunamis

  • Volcanic eruptions

  • Locusts

  • Sandstorms

  • Droughts

  • Forest fires

  • Avalanches

  • Solar storms

  • Fish die-offs

All of those events have different frequency of recurrence and all of them could be quite devastating. All of them are something expected to eventually happen, given a matching geography, population and technology level.

Some events, like a volcanic eruption of a nearby active volcano are enough to keep most people waiting for decades knowing that some day, the mountain will spit fire. People could also in advance dig trenches or walls to try to redirect lavas to somewhere else or at least slow them down.

Most old people living in farmlands remember of some severe drought that messed up with their lives. Many people store rain water, dig up artificial lakes or rely on big artificial irrigation projects as a preparation for that.


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