The Three Gorges Dam and Sea Level Rise

From the department of something-called-erosion:
In the 18 months since the Three Gorges Dam was completed, increasingly clear signs of environmental degradation have started to accumulate along the Yangtze, just as activists had warned. Among the most troubling have been incidents of geological instability in the soaring gorges that now embrace a reservoir stretching behind the dam across a good portion of Hubei province 600 miles southwest of Beijing.

Local officials acknowledge that dozens of major landslides have been recorded, affecting more than 20 miles of riverbank.

The Chinese, who had been talking about taming the Yangtze for a century, finally realized their dream of the Three Gorges in May 2006, when the dam was declared finished in a burst of national chest-thumping. From the beginning, Communist Party officials had acknowledged that the massive engineering project would entail environmental risks and upset the lives of riverside peasants. An estimated 1.2 million were forced to move to make way for backed-up water. But the damage could be controlled, the party and government insisted, and overall, the benefits still would outweigh the dangers.

The $24 billion dam played its assigned role in controlling the river during the annual flood season this summer. Moreover, the 7,575-foot-wide (almost 1.5-mile) structure has dramatically increased China's supply of clean electricity, producing 23.7 billion kilowatt hours in the first half of this year. The reservoir and swollen upstream river waters, reaching about 250 miles to Chongqing, have given the center of the country a trouble-free transportation lane.

But the breaking-in period has also shown how vast the environmental damage is likely to be -- and how expensive to handle. Lei Hengshun, an engineering professor at Chongqing University who has followed the Three Gorges project since its inception, said it has opened a "bottomless pit" of government expenditures that will have to go on for decades.

A group of hydraulic engineers and environmentalists reported in March that the overall number of landslides in the area, including small ones, surpassed 4,700, requiring reinforcement or evacuation of 1,000 localities.

Higher and less stable water levels behind the dam, now at almost 500 feet above sea level and scheduled to rise to 575 feet, already have altered pressure bearing on the base of majestic cliff sides, they explained, causing the perennially unstable ground to give way more often up and down the reservoir.
The Three Gorges Dam is one of the largest and most expensive dams in the world. In many ways it is a triumph of engineering and one of the most obvious pointers to Chinese technological and economic know-how. It is also clearly an environmental disaster. China seems to be very good at producing high-tech economic goods and services while, at the same time, contributing to problems in the global environment.

But then, of course, they did learn from us.

What really interests me about the article above is that it shows that dams don't just plug water up behind a wall. The water itself, now rising perhaps hundreds of metres over where it was before, is gouging out hills and causing all sorts of erosion in the process. Of course, all this will settle down over time since the dam is still only relatively new and the geography upstream still has time to adjust itself.

Now - think of Global Warming, especially the issue of rising sea levels. Given the massive impact that the Three Gorges Dam is doing with rising flood waters, think of the damage done to coastlines around the world if sea levels do rise. A rise of 1 metre may not seem much but we need to remember that, given this hypothetical rise in sea level, the damage done may result in the eventual erosion of areas exceeding 1 metre above sea level (depending upon the local geology). Moreover, any increased rainfall in areas may also increase soil erosion as well.

So, if you're saying to yourself "my home is 20 metres above sea level, I'll be okay", just remember that's what you thought as you watch your house tumble down a cliff and into the encroaching sea.

1 comment:

BLBeamer said...

I'll believe those catastrophic predictions when Al Gore and his ilk sell their waterfront property, even at a loss, to escape the impending deluge.