PHNOM PENH -- It was late at night when water from the engorged Prek Tnaut River started spilling into Yoeu Phally's two-story concrete house on the southern fringe of Phnom Penh.
"By 11 p.m., everything was floating," Phally, a rice farmer, told Nikkei Asia. "We never thought it would rise that high."
Nearby, monks at Wat Har Pagoda grabbed essentials before building a makeshift dike of sand and plastic outside a temple door in an attempt to keep floodwaters out.
"It happened quickly, in less than 20 minutes," recalled monk Mok Sok Ly. "The water came up to our necks."
Scenes like these have played out across the Greater Mekong region in recent weeks as tropical storms brought heavy downpours to Cambodia, Laos, Thailand and Vietnam. The resulting floods and landslides have killed scores of people, forced the evacuation of tens of thousands and caused widespread damage to property, infrastructure and crops.
Floods from the Mekong River and its tributaries annually inundate the landscape in Cambodia and its neighbors, playing a vital role in agriculture, fisheries and the environment. But the recent flash floods, which result from intense downpours, are the worst in years.
Coming on the back of a prolonged drought, experts say they appear in line with predictions that climate change will intensify extreme weather events.
In Cambodia -- ranked as one of the most vulnerable countries to the risks of climate change by ratings agency Standard & Poor's -- recent flooding has led to the deaths of at least 40 people, damaged dozens of garment factories, and impacted more than 130,000 families in 19 of the country's 25 provinces.
The crisis has turned the spotlight on the destruction of wetlands and lakes surrounding Phnom Penh that provide a natural flood barrier.
Prime Minister Hun Sen last week rejected criticism that the filling in of lakes played a role in the disaster, which he characterized as the "natural" result of too much rain.
Observers, however, say poor planning and government's disregard of water management in the city's expansion have exacerbated the problem.
Since 2003, developers of satellite cities and gated housing communities have filled more than 60% of the city's lakes and more than 40% of its major wetland areas, according to a report by rights group Sahmakum Teang Tnaut.
The most high-profile case has been that of Boeung Kak, once the municipality's largest lake, where thousands were forcibly evicted from their waterside communities after the site was granted to a private company led by a powerful politician in 2007 and then pumped full of sand.
The trend has continued. Plans to develop some 1,500 hectares of wetlands south of the city into a massive mixed residential and commercial zone known as ING City are proceeding, with a third already filled in.
In a study of the project's impact in June, STT found it could leave more than 1 million people vulnerable to increased flooding. The area receives nearly 70% of the city's rainwater and wastewater, and serves as a natural filtration system for runoff and sewage before it enters river systems.
Marc Goichot, a freshwater systems expert focused on Asia at the World Wildlife Fund, said it was "convenient" to "blame the sky" and focus just on climate change, but governments needed to take responsibility for the impact of land use change within flood plains.
"We are creating the conditions that expose us to more disasters," Goichot said. "We call them natural disasters, but they are man made."
Cambodia's construction industry has seen explosive growth in recent years, with investment increasing from $5.5 billion to nearly $11 billion last year, according to official figures cited by local media. Much of this growth has focused on Phnom Penh, now home to 2.1 million people.
With the city set to continue growing, Saber Masoomi, Cambodia's country director for the Wildfowl and Wetlands Trust, said water management needed to become a "core" element of urban planning and broader decision-making.
"We need to accept that this country is rapidly growing. Its economy, population and demands. That is the reality," he said.
"What is missing, is first an understanding of the socioeconomic patterns of the country and second a plan that clarifies how a tropical city like Phnom Penh can address its water security. Without a diversified and strong economy, it is difficult to only focus on wetlands."
Representatives from the Ministry of Land Management and the Ministry of Planning did not respond to requests for comment.
A Cambodian bureaucrat with a planning background working in Phnom Penh said it was widely recognized that in-filling the flood plains was going to add to flooding woes, but said "politics" made it difficult to override such projects.
"Ever since the 1400s, when the king moved the capital from Siem Reap to Phnom Penh, they've known the city has problems with flooding," said the bureaucrat, who requested anonymity. "You can never have success stopping the floods, but if they fill in the lakes it will be a disaster."
Ultimately, experts say the monetary value attributed to real estate reclaimed from wetlands could be far outweighed by the cost of losing their natural functions.
One research paper published last year estimated that wetlands slated for development in the south of Phnom Penh provided about $30 million of economic value annually in wastewater treatment, food and water provisioning.
Courtney Weatherby, a researcher at the Stimson Center, said replacing natural systems with architecture that depends on human-made engineering for managing water was often far costlier in the long term.
"Certainly development needs to happen, but those trade-offs need to be considered with clear eyes because when you look at many of these decisions to fill in wetlands, that trade-off wasn't even part of the equation," she said
Weatherby added that the principle of including water management in design has already been well established by renowned Cambodian architect and town planner Vann Molyvann.
Known as the man who built Cambodia, Molyvann completed more than 100 projects during the 1950s and '60s as head of public works and state architect.
He died in 2017, but his legacy lives on in several iconic buildings and speeches -- such as one delivered to a conference in 1999.
"Cambodia is a society of half earth, half water and cities should be built not by landfill but by incorporating water into their design," he said.