Opinion please - Pakistan flood partly man-made

‘Recent floods in Pakistan’s Indus Valley are of truly Biblical proportions’, the BBC writes on its website. And it asks: ‘Will the Pakistan floods strike again?’

The rainfall has been extreme. Last August, more than half of the monsoon rain fell in one week, whereas typically it is spread over three months. Professor Huib de Vriend, who works both at the faculty of Civil Engineering and Geosciences and at Deltares, blames the extreme precipitation on El Nino, which in Asia tends to lead to extreme rainfall. “During the last El Nino in 1998, China was hit and the Yangtze River flooded.”

“But rainfall is not the only cause of the flood. The capacity of the Indus’ river bed has decreased enormously over the last decades.” De Vriend explains that the Indus carries water, sand and mud from the Himalayas. However, because the water has increasingly been diverted for irrigation purposes, the Indus has had too little water left to transport its sediment to the sea. The consequence has been an accelerated silting up process, making the riverbed shallower and steeper, and thus reducing its flood carrying capacity. “It’s the consequence of some 50 years of irrigation”, De Vriend explains. “This has dramatically reduced the river’s flood capacity, so that any solid downpour will now lead to higher water and flooding.”

The BBC quotes professor Rajiv Sinha, from the Indian Institute of Technology in Kanphur, who basically shares De Vriend’s interpretation. But Sinha also adds that the problem has been made worse by deforestation. The BBC writes: “Trees protect the headwaters from erosion. But over the last half century, more sediment has been flushed down the river as forests have been cut.” Professor Sinha says: “What we’ve done is apply a system from the West that just doesn’t work in South Asia.”

Meanwhile, “Dutch development workers have been involved in setting up large irrigation structures in Pakistan”, De Vriend says. “The irrigation channels run through the sand, just like the Indus. I’m therefore not surprised that local scientists are well aware of the hidden causes of the floods.”
So is there any way back? De Vriend: “You can improve the river’s properties by applying a consistent policy of not using the river for irrigation. Store rainwater instead, reduce evaporation, and better retain the water. But to do so implies reducing agriculture in favour of long term security. In a political dilemma between short term benefits and long term goals, the short term usually wins out.”

“Our understanding of why the Indus Valley is prone to catastrophic floods is steadily improving”, BBC science reporter Howard Falcon-Lang states on the website. “However, this will be of no consolation for those displaced by the worst humanitarian crisis in a decade.”