Baghdad: The risk of Iraq's largest dam collapsing and unleashing a huge wave onto Mosul is affecting plans to retake the city from jihadists, an adviser to the premier's office said.
The army is deploying thousands of soldiers to a northern base in preparation for operations to recapture the city, the largest urban centre in the Islamic State group's self-proclaimed caliphate.
Concern has grown that a failure of the unstable dam, which is about 40 kilometres (25 miles) northwest of the city, could wipe out much of Mosul and flood large parts of Baghdad.
The Americans "frequently refer to Katrina" and say a collapse of the Mosul Dam would be "a thousand times worse", the adviser to the office of Prime Minister Haider al-Abadi told reporters.
Hurricane Katrina ravaged the US city of New Orleans in 2005, killing nearly 2,000 people and leading to a wave of violence and looting that completely overwhelmed the authorities.
"If the dam busts, the centre of Mosul goes under water by about a 40-50 foot wave (12 to 15 metres)," the adviser said, speaking on condition of anonymity.
"It just disappears, so 500,000 people (are) killed within a few hours".
He said another dam in Samarra, hundreds of miles downstream, would also burst. It is estimated the wave would still be several metres high when it reaches Baghdad.
A US assessment published Monday on the Iraqi parliament's website said Mosul Dam was "at a significantly higher risk of failure than originally understood."
'Nightmare scenario'
High-level contacts have taken place between the US administration and Baghdad, with Washington pushing for repair work to be undertaken urgently.
Since the dam's completion in 1984, Iraq has sought to shore up the foundation by injecting mortar-like grout into cavities that develop under the structure.
Regular minor seismic activity in the area is now seen as a potential threat.
There are also fears that IS could weaponise the dam.
"If the attack on Mosul goes well, there is a nightmare scenario that Daesh (an Arabic acronym for IS) could itself strike the dam as they withdraw from Mosul," the adviser said.
He said the US-led coalition, whose primary role in retaking Mosul would be to carry out air strikes, is concerned that a major bombing campaign could have an impact on the dam.
"They are worried about it, they are thinking carefully about what kind of munitions they use in the Mosul operation," he said.
Colonel Steve Warren, the spokesman for the international anti-IS operation, said the dam was far enough from Mosul for strikes not to be a threat to its integrity.
Another concern as Iraq begins deploying troops southeast of the city is a mounting economic crisis.
'Moral responsibility'
The government of Iraq's autonomous Kurdistan region is struggling to pay its peshmerga forces, who currently control the dam and will likely play a significant part in any Mosul assault.
Speaking in Rome on Wednesday, Abadi said "we have a moral responsibility, a national responsibility to guarantee the protection of this dam."
Iraq has awarded a contract to Italy's Trevi to repair and maintain the dam.
"We need to speed up the arrival of this company in Iraq and also to guarantee the security of its technicians and workers," said Abadi.
Italian Prime Minister Matteo Renzi, who has said Rome would deploy some 450 troops to protect the dam, stressed Wednesday that Iraq and Italy were "working together for the security of the area."
"When the Italian force comes in, the Italian force is responsible for the security of the dam, so there's no dispute over who's responsible," and Kurdish forces who hold the dam will withdraw, the adviser said.
He said Abadi hoped the contract -- estimated at 284.5 million euros (around $320 million) -- would be signed within two weeks. The World Bank is helping to finance it.
A warm winter could lead to early snow melt and Trevi is expected to swiftly begin work with a seven-month phase to repair the dam's lower gates. Another 18 months are needed for the rest of the major work.
