For Petch Cham, 35, a resident of Koh Dack, an islet in the middle of Cambodia's Tonle Sap river, the floods which swell the river each year are just a minor inconvenience.

``It is awkward walking about or riding my motorcycle in the flood waters, but I can live with them,'' said the taxi motorcyclist.

Petch Cham's ramshackle hut sits on stilts 1.5m above the ground. He said he has never feared the river even when it was swollen with the run-off caused by rains in lands further upstream.

The Tonle Sap connects with the Mekong, Southeast Asia's longest river, and flows into Tonle Sap lake, the region's largest freshwater lake.

``All I have to do is climb the stairs and live there for a week, maybe even a month,'' he said. ``We can live a normal life and use boats to travel about.''

But the floods in 2000 even caused Petch Cham some concern. ``I'm starting to fear floods. I have never felt like this in my 30 years of living with the river.''

And Petch Cham has every reason to worry.

At an international workshop on water policy issues in East Asia last month, water experts expressed the concern that floods across the Mekong region may get beyond people's control.

Sok Saing Im, the senior hydrologist with the Mekong River Commission, the inter-government organisation of lower Mekong countries housed in the Cambodian capital, said the floods of 2000 were the worst in two decades, wreaking havoc among towns and cities right along the river, from Chiang Saen district in Chiang Rai to Luang Prabang and Vientiane in Laos to cities further downstream in Cambodia and Vietnam.

The Commission estimates that up to eight million people had to be evacuated.

Sok Saing Im blamed man-made projects such as expanded townships, which were filling our rivers and seas with sediment, as a major contributor to the worsened flooding.

``But the most worrying [thing] is projects upstream that directly affect the downstream countries,'' he said.

When China filled a giant reservoir in Yunnan province in 1995, the water level in the Mekong in Cambodia was halved to 300cubm in just one day, he said.

In 2000, 20 Cambodians living along the border with Vietnam were drowned when Hanoi unexpectedly opened the Yali Falls dam on the Se San river.

Cambodia and Vietnam are also worried by the project initiated by China to improve navigation along the Mekong. This calls for the clearing of reefs, shoals and rapids, said Sok Saing Im.

Without these natural barriers, the river is expected to run more rapidly, making it harder for downstream countries to manage the regular flash floods that occur. Around 20 reefs in China, Burma, Thailand and Laos have been cleared this year to facilitate the navigation route.

Thailand, Laos and Burma signed an agreement with China on the river clearing in 1997. This calls for the deepening and widening of the navigation channel so the river can serve vessels of up to 500 tonnes. The idea is to bring goods from Yunnan province in China to Luang Prabang in Laos, rather than by the more costly and time-consuming South China Sea route.

Sok Saing Im said the Mekong River Commission was helping countries downstream to gather scientific evidence about changes in the river.

``Cambodia and Vietnam have not received much information on the project. They were only invited as observers to witness a reef blasting ceremony in December,'' he said.

Burma, China, Laos and Thailand have pushed forward relentlessly with the project, Sok Saing Im said. ``All the Cambodian government can do at the moment is wait for evidence to show that the project causes serious flooding.''

The Mekong River Commission has been collecting data on such things as the water volume and flow rate at its 400 water stations along the Mekong to prove whether the project has worsened flooding in Cambodia. This may be used to seek damages from upstream countries involved in the project.

``Man-made projects like dams may have changed the relationship between villagers and the river forever,'' said Ian Fox, a hydrologist and flood expert at Asian Development Bank.

Villagers used to live in harmony with nature, with floods part of their way of life. But development has changed all that, he said. The harmonious relationship has turned into an adversarial one.