Vietnam's Ho Chi Minh City is learning to live with floods but climate change has raised the stakes

HO CHI MINH CITY, Vietnam (AP) — It is the flood Vietnam's Ho Chi Minh City has learned to expect.

Forecasters warned on Sept. 27 that high tides could combine with heavy rain to increase the risk of flooding in Ho Chi Minh City, one of the world’s most climate-vulnerable cities . As heavy rain combined with the tide on the evening of Sept. 30, the Saigon river and smaller waterways spilled onto the roads of Vietnam's commercial capital.

Life went on. Floodwater lapped at diners’ feet as they ate their food at roadside shops. Street vendors sat under plastic raincoats beside their wares, while customers in ponchos rode up, bought what they needed and headed back into the water.

Residents of low-lying neighborhoods in the city have long learned to live with the water. Some, like 63-year-old Vo Dang Thi, have raised the floors of their homes to keep the water out. But familiarity does not make the flooding less disruptive, and climate change is making the city’s exposure worse.

“In cities such as Ho Chi Minh City, climate change is increasingly amplifying flood risk because it is interacting with rapid urbanisation and land subsidence,” Benjamin Horton, a professor of earth science at City University of Hong Kong, said in an email to The Associated Press.

A warming climate is raising sea levels and bringing heavier downpours. In mid-September, heavy rain caused flooding in several provinces in northern Vietnam .

The changes can overwhelm drains in Vietnam's largest municipal area, especially in densely populated areas, Horton said.

Nearly half of Ho Chi Minh City's land is less than 1 meter (3.2 feet) above sea level and its drainage and canal system was built during the French colonial time, when the population was about 2 million. The system has since been expanded, but a study by the U.K.-funded Global Future Cities Programme found it has struggled to keep pace with rapid growth.

At the same time, parts of the city were sinking because of groundwater extraction, leaving low-lying neighborhoods even more vulnerable to flooding. Pumping water from beneath the city can cause the ground to compact and sink as water is removed from underground layers, Horton said.

This means residents of vulnerable areas are at risk from floodwaters that can inundate homes and businesses, disrupt transportation, damage infrastructure, contaminate water supplies and increase public health risks, he said.

Nguyen Ngoc Thuong, 45, who runs a small eatery, said the water can reach knee height when the tide is high or it rains heavily.

“It takes more than two hours for the water to go down. Some customers just walk through the water and sit down to eat” she said.

Vietnam is seeking to overhaul the economy with a goal of becoming a high-income country by 2045. Ho Chi Minh City has merged with neighboring provinces to create a vast new megacity, bringing together industrial hubs, services and seaports across Vietnam's south with sharply differing landscapes and levels of urbanization.

Authorities quickly realized the existing drainage system, approved in 2001 and 2008, was no longer fit for purpose in the expanded city.

They launched a $13 billion plan in July to tackle 159 flood hot spots by 2030 including upgrades to flood-control infrastructure. That month, the city also adopted a climate action plan through 2030 to upgrade drainage systems and major canals, expand green spaces and improve its ability to cope with heavy rain, high tides and rising sea levels.

But the problem for the city is not simply heavy rain or high tides, Horton said.

Higher sea levels make it harder for rainwater to drain to the sea, while heavier rainfall can send more water into the city in a short time. In a sinking city, water also builds up faster and drains more slowly. As the climate warms, floods that were once rare can become more frequent, deeper and last longer, he said.

“Climate change is raising the baseline on which these events occur,” Horton said.

This is already happening elsewhere in the region. In Thailand, heavy rains have battered the country since mid-September, affecting more than 2.6 million people and killing at least 19.

For now, Nguyen Thi Nhua is keeping her stall open, selling banh gio, a Vietnamese snack made from steamed rice flour and filled with seasoned pork. She has been selling it from the same sidewalk spot for 12 years as the city has grown and through countless bouts of rain and high tides.

“There are still customers who stop by, so I just keep my stall open when it rains or the tide comes in,” she said.

Ghosal reported from Hanoi, Vietnam. ___

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