BANGKOK — As some of Thailand’s worst flooding in half a century bears down on Bangkok — submerging cities, industrial parks and ancient temples as it comes — experts in water management are blaming human activity for turning an unusually heavy monsoon season into a disaster.
A soldier pulled a boat as people and their belongings were evacuated from a flooded area in Ayutthaya province in Thailand.
The main factors, they say, are deforestation, overbuilding in catchment areas, the damming and diversion of natural waterways, urban sprawl, and the filling-in of canals, combined with bad planning. Warnings to the authorities, they say, have been in vain.
“I have tried to inform them many times, but they tell me I am a crazy man,” said Smith Dharmasaroja, former director general of the Thai Meteorological Department, who is famous here for predicting a major tsunami years before the one that devastated coastal towns in 2004.
The monsoon season this year has brought disaster to Cambodia, the Philippines and Vietnam as well as Thailand, where 283 people are reported to have died.
Thousands of people have been displaced as typhoons have battered the Philippines, and the country’s steep rice terraces of Banaue are reported to have been damaged by mudslides.
Floods have spread through Cambodia, where the city of Siem Reap is reported to be knee-deep in water, with floodwaters reaching the nearby temples of Angkor.
Thai officials are warning that, in the next few days, Bangkok could be inundated by a combination of heavy floodwaters from the north, unusually high tides and monsoon rains. People in some of the most threatened neighborhoods are building sandbag barriers around their homes and emptying shops of food, drinking water, batteries and candles.
Preparations in Bangkok have become frantic. About 45 miles of sandbags have reportedly been laid to reinforce a dike along the Chao Phraya River, which flows through the city. New flood barriers and drainage canals are being built. People are being told to stay alert.
As the water flows south from the inundated cities of Nakhon Sawan and Ayutthaya, with its submerged brick temples, the local news media have reported that 150,000 sandbags are moving south too, as soldiers truck them from one hard-hit area to the next high-risk point.
As the government rushes to protect some urban or industrial areas by diverting water from them, local officials have faced off over whose towns will be saved and whose will be sacrificed.
In Ayutthaya, two groups of villagers are reported to have battled over a dike that protected one side and condemned the other. As the unlucky residents dug at the dike to send the water toward their neighbors, a gunfight broke out, wounding one of the villagers. In some places, according to news reports, troops have been deployed to protect the dikes.
Among those stranded by floodwaters were 15 elephants, which climbed to the top of a wall a week ago to escape fast-rising water in Ayutthaya. They include seven mothers and their babies and a nine-year-old elephant known internationally for his painting skills with his trunk, said Ewa Narkiewicz, communications director for a group called Elephantstay, a nonprofit agency that cares for retired elephants.
“If proper help does not come soon, the mothers and babies are in grave danger,” Ms. Narkiewicz said. Each animal consumes up to 440 pounds of food a day, but the boats that could be used to ferry bananas, pineapples and sugar cane to them are busy rescuing stranded residents, she said.
Mr. Smith, the meteorologist, said the flooding situation this year had been aggravated by bad water management.
“They miscalculated the water levels and did not discharge water from the dams early enough in the rainy season,” he said. “The dams are almost full now, so they discharge the water at the same time, and all the discharge water comes down to the low-lying areas.”
Those areas become obstacles to the free flow of water, he said, as developers continue to extend their activities.
“They build their estates in low-lying areas that are supposed to be reservoirs,” he said, “and they throw up a dam or a dike, and they block the flow where the water is supposed to go in rainy season.”
Once the floodwaters reach Bangkok, they will pour into a city that has lost its natural defenses: a huge network of canals that have been filled in — or clogged with garbage — as the city has become an overcrowded behemoth.
“Our city plan is inefficient,” Capt. Somsak Khaosuwan, director of the National Disaster Warning Center, said by telephone.
“The weather hasn’t changed that much,” he said. “We always have more water in the rainy season. But if we don’t have integrated water management, we will face this problem again next year.”
Man and nature are increasingly estranged, he said, and their coexistence is becoming a battle. “This is the sign that we should preserve the forest,” he said. “We’ve hurt nature for a long time, and right now it seems that nature wants to pay us back.”
Poypiti Amatatham contributed reporting.