Will the Pakistan floods strike again?

The recent floods in Pakistan's Indus Valley are of truly Biblical proportions.

The UN estimates that the humanitarian crisis is now larger than the combined effects of the three worst natural disasters to strike in the past decade

These include the Asian tsunami and the major earthquakes that devastated Kashmir and Haiti.

The headline figure of 1,700 killed masks the real scale of the disaster that has displaced 14 million people.

As I write, the southern city of Hyderabad, with a population of 1.5 million, stands on the brink of inundation as peak floodwaters surge downstream.

Scientists have described this catastrophe as a once-in-a-century flood.

But could climate change mean that floods of this magnitude, or even bigger, become a more regular occurrence?

"Rivers just can't cope with all that water in such a short time,

It was five times, maybe 10 times, more than normal”
Rajiv Sinha Indian Institute of Technology

The "Great Mother"

The Indus is one of the world's great rivers.

From its headwaters in the Himalayas of Tibet, it flows north-west through India before turning sharply south across Pakistan. It finally discharges into the Arabian Sea, a journey of some 3,200km (2,000 miles).

Although some of its water comes from melting Himalayan glaciers, the vast majority is dumped by the summer monsoon.

As torrential rain sweeps in from the Indian Ocean, floods are triggered almost annually.

Humans have had long experience of Indus floods.

Its floodplain was an early cradle of civilisation 9,000 years ago. Here people first gave up their nomadic ways to farm livestock and cultivate crops.

Today, the Indus Valley is home to 100 million people, who rely on it completely for drinking water and irrigation. To many, it is "the Great Mother".

Yet, as the catastrophic floods of August 2010 demonstrate, the Indus is both friend and foe.

History lessons

Geologists are working round the clock to better understand the ancient flood history of the Indus River.

Such history lessons will help to better predict its erratic behaviour and "plan for our own uncertain future", said Professor Peter Clift of Aberdeen University, an expert on the Indus River.

His team recently used makeshift "rigs" to drill down into the sands and mud of the Indus floodplain. By precisely dating layers of flood-deposited sand, they were able to work out past changes in river flow.

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