"These barrages [dams] have significantly lost their design capacity due to deposition of silt loads," noted Mushtaq Gaadi, an expert on the Indus water basin and a professor at Quaid-i-Azam University. "Both Jinnah and Taunsa barrages experienced the failure."
Wreckage blocks flood control channels
The crumbled mess of bridges and buildings upstream compounded the problem, creating in some places inadvertent dams that held back floodwaters briefly before releasing them en masse downstream, adding to the misery.
According to Pakistani government officials, their nation boasts the largest contiguous irrigation network in the world. Along with three massive dams, more than 4,000 miles of levees and numerous smaller dams, the system includes an intricate network of "link canals" designed to channel waters from westerly rivers eastward, to feed Pakistan's richest farming areas.
Government engineers say the system is a valuable flood control instrument, as it expands the area available to channel excess water, but this year, even this system was overwhelmed.
In Punjab, the government has in place designated breaching areas, where levees are packed with explosives that can be detonated in the event of excessive flooding. Deliberate breaching is necessary to prevent damage to the barrages, but officials failed to prevent populations from sprouting up in the areas designated as flood control zones. As a result, government water managers admit they were forced to flood thousands of homes to spare barrages and other floodworks.
Still, unintended breaches occurred throughout the system, caused by levees that failed largely because national and provincial authorities didn't bother to pay for their upkeep. It all accumulated into a man-made disaster that could have easily been averted or made much less worse, said professor Gaadi.
"I can say with certainty that the multiple engineering failures have exacerbated the flooding hazards in several ways," he said. "The design capacity of many barrages (Jinnah, Taunsa, Guddu, Sukkur, etcetera) proved insufficient due to rising riverbed. The breaches of embankments at or around barrages, deliberate or natural, thus became imperative."
In addition, irrigation works designed to avoid mass flooding incidents "either disrupted the flood flows or became the main vehicle for their transportation beyond the riverine areas," Gaadi added.
Gaadi says he has uncovered evidence that a World Bank-financed rehabilitation project around the Taunsa Barrage made things worse. Culvert dams put in during construction weren't removed once the $123 million project ended in early 2010, said Gaadi, pushing water over the left bank and flooding out villages the project should have saved. Seventy affected people began a three-day protest in front of World Bank offices in Islamabad to draw attention to the controversy.
Pakistanis active in the flood emergency response paint a more sinister picture to explain flooding in Sindh province, where no purposeful breaching systems exist. Here levees broke anyway, conveniently diverting floodwaters around prime agricultural land owned by wealthy politicians, swamping poor villages instead.
Deliberate levee breaks to save the wealthy?
The fact that much of the floodwaters in Sindh have yet to reach the sea is fueling heated speculation of tampering. Government sources refused to comment but say that an investigation is under way. The Sindh provincial government has appointed a commission to investigate deliberate breaks.
"The possibilities of deliberate breaches cannot be ruled out, whatever may be the findings of the inquiry," said Meer Muhammed Parihar, former secretary of Sindh's Irrigation and Power Department.
Population growth and settlement patterns also factored into the massive extent of the damage.