China’s annus horribilis continues. Floods across swaths of southern provinces that have claimed the lives of 171 people and forced the evacuation of almost 1.7 million look set to worsen, as torrential rains continue to pound the region.

In the densely populated province of Guangdong, which abuts Hong Kong, officials are warning of a “black June” as high tides, heavy rains and two converging swollen rivers threaten levees and force the closure of factories in one of China’s economic powerhouse regions.

People’s Liberation Army troops were scrambling to shore up sodden banks with sandbags amid forecasts of yet more heavy rains in central and southern China that could even trigger flooding along the country’s second-longest waterway, the Yellow River.

Damage in the far south was described as the worst in half a century. The Guangdong water resources office said: “The Pearl River Delta river network has suffered not only the biggest-volume floods in over 50 years but simultaneously also the highest tides in over 10 years."

Rarely a year goes by when China does not suffer floods, drought and other disasters somewhere on its huge landmass. But this year has been among the worst for decades. The cost of the latest flooding has yet to exceed damage in previous years and is much less then losses from devastating winter storms that crippled much of southern China with rare snow and ice. It has however compounded difficulties for the residents of the southwestern region hit by the May 12 earthquake that killed more than 70,000, with the bad weather impeding aid and reconstruction efforts.

In Wenchuan County, epicentre of the 8.0 magnitude tremor, troops were struggling to reach about 20,000 people threatened by landslides as heavy rains approached. More than 52,000 had already moved from threatened areas.

China’s leaders are anxious that the storms in the south could exacerbate inflation and foment social unrest. Officials have said China’s sugar crop could suffer damage if the wet weather continues for another week. And Nestle, the world's largest food group, halted production at its only coffee plant in China, based in Guangdong, because of flooding.

There were also signs of localised price spikes, a worry for officials with inflation near its highest in more than a decade.

In the suburbs of the Pearl River delta city of Dongguan, farmers battled to save their crops. Farmer Liang, 64, tended a small patch of yams, lotus and other vegetables on the banks of the river. "The water came up to here," Liang said, pointing at a spot on the levee about 10-12 feet above the water level. "It washed away all my cabbages."

The typhoon season has begun, ensuring further disaster for the coast of sub-tropical Guangdong, home to 110 million permanent and migrant residents, over the summer.