Bangkok, Thailand (CNN) -- The worst flooding to afflict Thailand in half a century could take more than a month to recede in some areas, the Thai government said Sunday.
The country is also bracing for more high tides in the coming week, according to Thailand's Flood Relief Operations Command. High tides cause rivers to back up, subsequently raising water levels.
Thai Prime Minister Yingluck Shinawatra said authorities are trying to drain water into the sea as quickly as possible, but the disaster has proved arduous.
"I would like to apologize to the public because it has been difficult to make advanced notice about the floods," she said, according to the Thai News Agency. "There are many factors beyond our expectation. Informing too early could cause panic and mistakes could happen easily, but people should be alert and closely follow up the situation."
The government has set up more than 1,700 shelters nationwide, and more than 113,000 people have taken refuge inside.
"Since the flooding situation might persist for four to six weeks in many areas of the country, the Government has prepared several plans to improve the living conditions in various evacuation centers," Thailand's government public relations department said Sunday. "The plans include occupational training and lesson teaching aimed at generating employment for the affected people after flood water recedes."
The government had hoped that strengthening flood barriers and widening canals would keep populated areas safe.
But now the government is trying a different technique: opening floodgates to relieve pressure on dams and levees and send the water toward the sea.
The decision to divert water through canals in Bangkok means parts of the city, and its surrounding suburbs such as Rangsit, are flooded.
By Sunday, diversion tactics used by the government starting to work in eastern Bangkok, where water is starting to recede. But areas west of the Chao Phraya River --- which has burst over its banks -- remain a concern.
The flooding, which follows months of monsoon rains, has already killed 356 people, with nearly 9 million others affected, authorities said.
Overall damage from the floods could top $2 billion, with the worst yet to come as the waters destroy shops and paralyze factories nationwide, the Thai Finance Ministry said.
Thailand derives a significant portion of its revenue from tourism.
Many residents waded through dirty water in the capital in recent days as they made a desperate attempt to save their belongings.
Rising water in Rangsit gave residents little chance to save what they could.
Some moved out of flooded homes by boat, or anything that could float. The rest waded through water with plastic bags balanced on their heads.
Pets were tucked into coats or pushed inside boats. Children, meanwhile, seemed to struggle to stay on their feet against the fast-moving water.
The prime minister has urged all Bangkok residents to move their belongings to higher ground as government workers try to contain the flooding.
Government spokeswoman Thitima Chaisaeng said the move was a precautionary measure.
To protect their cars, residents double parked along elevated highways, making it nearly impossible to navigate a city where traffic is congested on a normal day.
CNN's Kocha Olarn and Karen Smith contributed to this report.