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Lessons from China’s natural flood control

Lessons from China's natural flood control 2

Lessons from China’s natural flood control

The rainy season in southern China this year lasted nearly twice as long as usual.

`The rainy season normally lasts about 24 days, but this year it’s up to 43 days,` Xiquan Dong, an expert on extreme weather at the University of Arizona, USA, said about recent weather developments in China.

Three Gorges Dam in Hubei province, China, released floodwater on July 19.

However, the level of damage from this year’s floods is not as catastrophic as the historic floods in 1998. Some environmental experts believe that this result is due to natural disaster mitigation strategies based on

`This year’s rainfall is much higher than in 1998, but the floods are less severe and cause less damage,` said Liu Junguo, head professor of the School of Environmental Science and Engineering at the University of Science and Technology.

According to China’s Ministry of Emergency Response, this year’s floods left 158 people dead or missing, and more than 400,000 houses were destroyed.

The Chinese government attributed the 1998 floods to unusually heavy rains as well as widespread deforestation and high population density along the Yangtze River and its tributaries.

According to Professor Liu, the 1998 disaster forced the Chinese government to rethink its entire flood planning and management strategy.

Lessons from China's natural flood control

Shangrao city, Jiangxi province, China, was flooded with floodwaters in July. Photo: Reuters.

`This is definitely a very important turning point in the Chinese government’s thinking on the relationship between humans and nature,` Liu said.

For centuries, China’s flood control strategy has mainly relied on dikes built on the banks of rivers, to separate the overflowing river water from the living and farming areas of the people on the other side of the dikes.

However, the dyke system that has sprung up along every river has caused flood waters to rise higher, creating greater and greater pressure on the increasingly overloaded and degraded dykes.

In order to overcome the damage caused by the overloaded dyke system, China has launched a number of major ecological restoration projects, planting billions of trees to prevent mountain water from flowing into rivers and retain more water.

`The Chinese government has initiated a lot of forest restoration programs,` Liu said.

Liu said his studies show that depending on the context and terrain, afforestation can help reduce flooding by up to 30%.

In addition, the Chinese government is actively implementing `sponge city` projects with the goal of increasing green spaces and absorbent sidewalks to absorb more rainwater in urban spaces.

According to Jeff Opperman, freshwater scientist at the World Wildlife Fund, China’s new strategy also focuses on restoring the original status of alluvial areas along the Yangtze River.

`Mudflats are a type of natural terrain. Rivers tend to rise and overflow into the mudflats on a relatively regular basis seasonally,` Opperman said, adding that moving people out of the floodplains will

According to him, ideally the government should have policies to prevent people from living at high densities in mudflat areas from the beginning.

After the 1998 floods, the Chinese government persuaded 2.4 million people to leave the land along the Yangtze River, restoring nearly 2,600 square kilometers of mudflats.

Liu assessed these nature-based interventions as effective.

However, according to David Shankman, an expert on Chinese floods at the University of Alabama, USA, convincing tens of millions of people to relocate from the Yangtze River floodplain is almost impossible.

`It is the center of China’s rice granary,` he said.

Many families have lived here for many generations and they do not want to give up farming.

China has invested billions of dollars building dams on the Yangtze River and its tributaries.

Lessons from China's natural flood control

People watch the flood discharge scene of Tammen Ha dam in Henan province, China, June 30.

Critics are skeptical about the dam’s effectiveness, and some have expressed concerns that the dam could be damaged as water pressure increases upstream.

Expert Xiquan Dong from the University of Arizona said climate change will make above-average rainfall common along the Yangtze River.

`With climate change, ocean temperatures will increase, causing more water vapor to form in southern China,` Dong said.

A series of studies conducted over the past decade have confirmed Dong’s findings.

China’s large-scale flood management projects can help the world learn what works and what doesn’t, said Cecilia Tortajada, a water policy expert at the University of Singapore.

`In terms of flood water management, they’ve learned a lot,` she said.

Countries should prepare for a world in which more intense floods will occur.

`Floods will not go away,` she emphasized.

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