Earthshots: Satellite Images of Environmental Change

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The population of China has been urbanizing at a rapid rate. In 1978, less than 20% of China’s population lived in cities. In 2015, more than 55% of the population of China was urban, and that rate is climbing. By 2030, the country’s urbanization is projected to reach 70%. That will be about 1 billion people living in cities in China.

The Shiyan Municipality, Hubei Province, presents an interesting example of urbanization. The population of Shiyan increased from 333,089 in 1990 to 724,016 in 2010. To accommodate the increased urbanization in the Shiyan region, as in other regions of China, engineers have found an innovative way to create more land for building—flattening mountaintops.

This Landsat series of natural color images shows the rapid development occurring on leveled land around Shiyan, along with changes seen to the Danjiangkou Reservoir nearby.

Map of the featured area.

Shiyan, China, was a small village in the mountains until the 1960s. That’s when a lot of industrial production was established there in its relatively safe mountainous regions. However, because of the mountainous terrain, Shiyan did not have enough land to offer for expansion. So the industry moved away in 2003.

To prevent that from happening again, the city began planning to create new land for development in 2007. Drastic changes can begin to be seen in the imagery by the 2008 Landsat image.

Shiyan is now a famous production base for automobiles. Dongfeng Motor is headquartered in Shiyan. Other major industries in Shiyan include pharmaceuticals, textiles, and chemicals. Shiyan is also one of the central tourist centers in the northwest of Hubei Province.

To create this new land for building, they are leveling mountaintops and filling in valleys. Explosives level the hills, and fleets of trucks haul away the soil. This rock and soil is then used to fill in the valleys.

This additional land that can be developed can ease pressure on land that is valuable for agriculture elsewhere. It creates land for cities to expand where they could not do so previously. Most of the new land is for warehouses and industry. A small amount is for housing.

The bright spots in the images show the leveled and cleared land. These areas are then quickly replaced by industrial centers.

A Sentinel-2 image from February 2016 shows a bit more detail than Landsat. This close-up view of Shiyan shows the industrial development and land clearing at 10-meter resolution. Blue-topped rooftops are buildings for industry; light tan spots are leveled land.

The hills that are being flattened vary in height from 100 to 150 meters. The material used to level the hills is used to fill valleys. However, building on this infill might not be best for urban construction. The soft soil from the infill subsides easily and is prone to landslides.

Other environmental problems are cropping up based on this land leveling. The process of moving this much material throws dust particles into the air. Changing hills to plains has caused soil erosion, which adds sediment to local water sources. Shiyan is near the headwaters of the South-North Water Transfer Project, a huge project that diverts water to northern China. The sediments can end up in waterways, polluting the water. Furthermore, it can take years for the flattened ground base to be stable enough for building.

Visible in these images is one canal associated with the $62 billion South-North Water Transfer Project. Water resources are a concern in China because freshwater is distributed throughout the country unevenly. The south has abundant freshwater, but it’s scarce in the north. This project is an attempt to alleviate the water shortage in the north.

The entire project has three different canal routes that link China’s four major rivers (the Yangtze River, Yellow River, Huai River, and Hai River). The central route brings water from the Danjiangkou Reservoir north to Beijing. The reservoir was formed by the Danjiangkou Dam, completed in the 1970s. The height of the dam was increased from 162 to 176.7 meters above mean sea level between September 2005 and September 2013.

On the east end of the largest portion of the Danjiangkou Reservoir, a bright line extends to the east and north. This canal takes water from the reservoir 1,400 kilometers to Beijing. This water will benefit over 100 million people.

Construction of this central route of the South-North Water Transfer Project began in December 2003. Beijing began receiving water from the reservoir via the canal in 2014. The entire project is the biggest interbasin transfer scheme in the world.


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