According to a report by the Department of Drainage and Sewerage, the annual clearing out of city drains was unable to be completed on time in many districts.

Only 22 per cent of Phra Khanong drains and 32 per cent of Bang Phlat's drains have been cleared, along with 56 per cent of Nong Khaem drains and 80 per cent of Chatuchak's system.

All drains should be completely cleared by May in preparation for the rainy season.

The annual dredging work in Bangkok is normally done by city council workers and about 2000 well-behaved inmates in a six-month spell from November to May the following year.

But the work was halted in May because the Corrections Department was unable to provide enough well-behaved inmates who could be allowed out to help complete the work.

Deputy Bangkok Governor Banasopit Mekvichai said it

was a big problem that would

cause floods in the city and the Bangkok Metropolitan Administration would urgently consult the Corrections Department to try to prevent the problem recurring.

Pornsawan Kerdpokha, the departmental official who oversees the inmates' social work, said up to 25,000 prisoners had been granted royal pardons to celebrate the 60th anniversary of His Majesty the King's accession to the throne. This caused the public work to be stopped.

"A huge number of well-behaved prisoners returned home this year [and] it takes some time to select new inmates who are qualified for working outside," she said.

Only well-behaved male prisoners are selected to work outside jails.  They must have completed more than half their terms, have less than two years to serve and be free of drug-related allegations to be eligible.

"However, we may be able to provide a new group of inmates for the dredging work this month," Pornsawan said.