Italy's mountainous and unstable geography has always made the country vulnerable to natural disasters, from floods to landslides and earthquakes.

Genoa, between the sea and a ring of steep mountains, is particularly exposed to severe storms and flooding.

But administrative failures under successive governments, from unregulated building to poorly planned infrastructure and bureaucratic inertia, have exacerbated the problems.

"It's a mass of problems together. You have houses built in the wrong places, inadequate water-channelling systems, poor planning and administration," said Carlo Malgarotto, president of the Liguria regional council.

The city also came under criticism for not learning the lessons from the deadly floods in 2011.

"What is really alarming is how little has been done in three years to make Genoa secure from another flooding disaster," said Francesco Vincenzi, president of ANBI, a national association representing the organisations charged with overseeing flooding and water-safety issues.

Italy's deep economic crisis, which has seen public spending pared back to the bone in many areas, has made handling unexpected disasters more difficult, but deeper systemic weaknesses have also been highlighted.

"The problem of water security in Italy isn't mainly to do with resources, it's about political will and bureaucracy," Vincenzi said.

Governor Claudio Burlando estimated the damage to public infrastructure at some €200 million (HK$2 billion) and as workers and volunteers began the cleanup, Franco Gabrielli, head of the civil protection authority, warned that the problems would persist over the weekend.

"We are still in full emergency," he said. "The forecasts for the next few hours offer no relief at all for [Sunday] and Monday."

He admitted that authorities had failed to predict the huge volume of rain that fell in the space of a few hours. Parts of the city saw 700mm of rain fall in 72 hours, not far short of the average rainfall of an entire year.

But he criticised delays in reinforcing the banks of the Bisagno River, the biggest in Genoa, which burst its swollen banks late on Thursday, and said it was a "scandal" that €35 million set aside for the work after the 2011 floods had not been spent because of a legal dispute.

The archbishop of Genoa, Angelo Bagnasco, called for "timely and massive" action by government to resolve the crisis and prevent similar disasters in future.

"Everyone knows what their responsibilities are," he said.

"It's absurd and shameful that bureaucracy of any kind should be blocking funds that are absolutely necessary for resolving these problems."