The swollen Chao Phraya River spills out of its banks in Pathum Thani province, north of Bangkok, Thailand, on Oct. 17, 2011. The province, lying upstream of Bangkok, has already suffered major flooding. (AP Photo/Sakchai Lalit)

Flood barriers protecting Bangkok are being tested as some of the highest historical flood waters make their way to the sea.

The death toll has reached at least 315 people with another three missing, Australia’s ABC said on Tuesday.

More than a million sandbags have been filled, many of them to be laid atop existing dikes.

Tens of thousands of workers have been evacuated from the Navanakorn industrial estate following the failure of a flood barrier. As late as Monday, the estate was “dry and declared safe by the government,” ABC said. There are 200,000 people working on factories and living in apartments on the estate.

Talk of sacrificing some areas to save those of greater economic significance was reported. This would involve opening of upstream sluices to prevent total inundation of Navanakorn.

An ongoing fight to protect the Don Mueang area has included the building of a new flood wall. Don Mueang is the site of one of Bangkok’s main airports.

Unusually high monsoon rainfall reaching back as far in time as July has been the trigger for the severe, far-reaching inundation.

Flood waters from the nation’s hinterland have gathered into the lower reaches of the Chao Phraya, the major stream that meets the sea near Bangkok.

Owing to the low river gradient and flatness of the land, the flood threat will persist in Bangkok for some time to come. Authorities have said that another month will likely be needed before the voluminous flood surge finds its way into the sea, according to ABC.

Mid-October is about the time that the summer monsoon, with its plentiful rain, typically winds down in central and northern Thailand, the areas hard hit in 2011.