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Nov
10
2009
Ancient Chinese road construction method preserves cliff ecosystems
A technique used to build cliff paths during China’s Qin Dynasty could protect fragile ecosystems against the damage usually caused by mountain road development, scientists report in Landscape and Urban Planning.
Cliffs can house unique communities of trees, lichens, birds, and small animals. But human encroachment onto mountainous regions is “eliminating species from these sites even as scientists discover them,” the team writes.
To preserve these natural habitats, China has turned to an ancient road construction method called cantilevering that was practiced around 200-300 BC. During that time, engineers built hundreds of kilometers of cliff paths by inserting wooden beams into holes in the mountainside, covering the beams with planks, and propping up the road from below with additional supports if necessary.
The same technique, updated with modern materials, was recently used to rebuild a mountain road in China’s Hubei Province. Researchers monitored eight cliff sites during three years of construction and found that, on average, only 11.1 square meters of vegetation was damaged at each location. In contrast, the conventional construction method of creating a tunnel and filling in the slope below the road would have caused an average of 362 square meters of damage per site, they estimate.
The ancient technique also required moving 97.8 percent less sand and soil than the conventional method, lowering the likelihood of erosion and the impact on nearby rivers and streams. A cantilevered road with underlying supports was 17.4 percent cheaper than a conventional road, and a cantilevered road without supports was 85.6 percent cheaper, the authors write. If adopted, they say, the technique could not only protect biodiversity but preserve the stunning mountain views valued by tourists. – Roberta Kwok
Source: Cao, S., Ye, H., & Zhan, Y. (2009). Cliff roads: An ecological conservation technique for road construction in mountainous regions of China Landscape and Urban Planning DOI: 10.1016/j.landurbplan.2009.10.007
Image © scionxy, iStockPhoto.com
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