Phnom Penh residents rate floods as the city’s top disaster hazard, with fires and toxic waste placing second and third, respectively, according to a study by Czech NGO People In Need and Cambodian NGO Sahmakum Teang Tnaut.

Experts said that flood risk has been elevated since the capital filled in 25 natural lakes for real estate developments. Meanwhile, an insufficient drainage system that’s frequently clogged by residents’ garbage or blocked by construction can’t get rid of the water quickly enough.

“Disaster hazards tend to concentrate in the outer districts of Phnom Penh,” the authors wrote in the study, which was quietly released in December but publicised via social media over the weekend. “These parts … are less developed and have fewer protection mechanisms.”

The most at-risk communes include Sak Sampov, Srah Chak, Samraong Krom, Prek Tasek and Phsar Doeum Thkov, with the greatest risk coming between August and November. Over the past 15 years, more than 36,000 households have been affected, 2,569 residences damaged or destroyed and 39 people killed by flooding.

San Chey, coordinator for ANSA-EAP, which monitors infrastructure, said that Phnom Penh’s drainage system is insufficient, and old and new drainage systems are poorly linked, limiting their ability to drain water.

Meanwhile, the surge of people moving to the capital and not paying attention to solid waste disposal has made problems worse, said Chey.

Piotr Sasin, country director of People In Need, said that developments like roads or buildings block water from finding a low point to drain into, which leads to pooling and flooding.

Ee Sarom, executive director at STT, said that City Hall hasn’t taken sufficient action to solve this problem.

“My assessment is that [the government] did little to help,” he said. “We have 25 lakes that have been filled in by the Phnom Penh City Hall. This is one of the causes of the flooding.”

Mean Chanyada, head of Phnom Penh’s administration department, said the assessment was accurate in labelling floods as the biggest problem but argued that the government has “achieved a lot” with the help of the Japan International Cooperation Agency.

“[We recently replaced] more than 100 kilometres of drainage pipes to make them wider. Our [total] drain pipes are more than 400 kilometres long. This year we could reduce flooding in the city by great amounts.”

Japan wants to help Cambodia’s largest cities improve their water infrastructure, according to a delegation that visited Phnom Penh in January.