Over four pages, The Times Higher explores the long-term impact of the Indian Ocean tsunami and examines what can be learnt from past natural disasters

The tsunami has brought its share of conspiracy theories and speculations, including that I foresaw this disaster.

In my first book about Ceylon, The Reefs of Taprobane (1957), I did indeed write of a tsunami's impact on Sri Lanka. I wrote about how, in 1883 after the Krakatoa earthquake, the water had suddenly drained from Galle harbour and how the people had "rushed to high ground as quickly as they could".

This intrigues me: what made them rush to high ground when in 21st-century Sri Lanka many died because they rushed out to see the suddenly receding sea?

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Devastating as they are, disasters have been a favourite element of storytellers over millennia. Many of my books deal with disasters, but perhaps my 1973 book Rendezvous with Rama contains the most important message for policymakers.

It opens with an asteroid impact on Europe that obliterates northern Italy.

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Such life-threatening impacts are more frequent than many people realise: there were three known ones in the 20th century alone, but all, miraculously, in uninhabited areas. It is only a matter of time before our luck runs out.

In Rama , I argued that as soon as the technology permits, we should set up powerful radar and optical search systems to detect Earth-threatening objects. This has now been widely accepted, but astronomers' efforts are woefully underfunded.

When the possible consequences of asteroid impacts on Earth are discussed, people seem to be comforted by the fact that two thirds of the planet's surface is ocean. In fact, we should worry more: an ocean impact can multiply damage by triggering the mother of all tsunamis.

Duncan Steel, an authority on the subject, has done some terrifying calculations that show that waves triggered by the impact of a modest-sized asteroid will carry a massive energy, equivalent to 60 megatons of TNT.

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These waves can travel long distances, causing much more diffused destruction than the land impact of an asteroid, where hills, buildings and trees mitigate the effects.

Contrary to popular belief, science-fiction writers don't predict the future - we try to prevent undesirable futures. In the wake of the Asian tsunami, scientists and governments are scrambling to set up systems to monitor and warn us of future hazards from the sea. But let us keep an eye on the skies as we worry about the next hazard from the depths of the sea.

Although he lost his diving school in the recent tsunami, Sir Arthur C.

Clarke has no plans to leave Sri Lanka. He thanks Nalaka Gunawardene for his support in writing this essay.

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