WHILE allout efforts by the government and people are needed to rehabilitate the flood-affected people and infrastructure, we also need to think as to whether it could be termed purely a natural disaster.

The climatic patterns are changing drastically which, in turn, is caused by the increasing concentration of the greenhouse gases in the atmosphere due to human activities.

According to a 2007 study by Oxfam, floods and windstorms increased from 60 events in 1980 to 240 in 2006, with flooding itself up by six-fold (Nov 26, 2007).

Besides the climate change, there are however certain local factors that exacerbated the destruction by floods.

With a basin area of 963,480 square km and 2,898 km length, the Indus ranks the 19th in world, and 17th by water volume of 269.1 cubic km per year. This Indus is also called the Lion River. Records before the construction of any dam or barrage tell us that its breadth stretched over several miles in its lower reaches, and it carried a silt load of up to 300 million tonnes a year to the delta.

There it contributed to average three square miles increase in the deltaic land each year.

Over the past century, this lion has been tamed by a number of dams and barrages, and confined within artificial embankments into a breadth less than one-tenth of its original breadth.

This should not have happened to this river; but with huge water diversions for agriculture and other purposes the river had been unable to fill even this limited space for most of the years, except for once in a decade by high floods.

The burgeoning human population encroached upon the river bed in the plains and the hill slopes in the catchment area of the Indus and its tributaries.

With agriculture being the major culprit in accelerating the erosion of soil, tilling the hill slopes must have increased the silt load of Indus and its tributaries by several-fold.

But instead of reaching the delta, this silt had been depositing in the reservoirs of dams and in the river bed itself. The shallowing of river further decreased its capacity to hold water.

In the wake of the unprecedented heavy monsoon rains this year, the lion came back roaring to its erstwhile majesty. With such a limited space available for this huge amount of water, the destruction was inevitable.

The only way to mitigate the floods in future is to give the river its natural space by moving the human settlements away from the river bed; and by controlling erosion in the catchment area by abandoning agriculture and logging of timber on hill slopes, reforesting them strictly with those tree species that were originally present there naturally.

PROF SURAYYA KHATOONUniversity of Karachi