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    1. Erosion Control
    2. Vegetation Management

    The Three Gorges Project: When Flood Control Means More Than a Dam

    March 1, 2003
    Beijing, China, July 31, 2002. The initial reason to sign on a six-day cruise up China’s Yangtze River was the scenery, which in itself would have been enough, given that most of what we saw will soon be lost. Almost half of our 1,352-km (840-mi.) voyage was to have been in the Three Gorges, where the Yangtze rushes through 914-m (3,000-ft.) limestone cliffs, some so narrow and steep it’s said sunlight never reaches the water. Hidden shoals and treacherous currents are so numerous that ships must navigate 37 one-way channels. Once on the water, it was easy to lose track of the scenery and become distracted by the functional problems of containing this unruly river, especially in light of the controversy surrounding the Three Gorges Dam, the Chinese government’s latest and most massive attempt to control this mighty river, which has created havoc in central China for centuries. The Yangtze is China’s longest river, the third longest in the world after the Amazon and the Nile and the third largest in terms of runoff after the Amazon and the Congo. The Yangtze gives with one hand what it takes away with the other, depositing rich soil in its delta but causing devastating floods in its vulnerable middle reach. In the 2,200 years of Imperial rule that ended with the Qing Dynasty in 1911, the Yangtze has caused 214 major floods, on average one every 10 years. The last century began with the dual flooding of the Yangtze and the Han rivers in 1911, which was followed by four major events: in 1931 almost 150,000 lost their lives when an area the size of New York state was inundated and 3 million ha (7.4 million ac.) of farmland were ruined; 142,000 people died in a flood four years later; in 1954, another 40,000 lost their lives and floodwaters suspended operations of the railroad between Beijing and central China for four months; and when the river rose in 1998, 3,000 people died, 5 million homes were lost, and 21.8 million ha (53.9 million ac.) of farmland were submerged for a damage total of $30 billion.

    A model for the completed dam. The cruise ship passed through a temporary diversion channel at the south end of the spillway, around the second breakwater (foreground). Although the Chinese have long been at the mercy of the Yangtze, damage in recent floods has been compounded by development. The total volume of water in the 1954 flood, for example, was greater than in 1998, but the 1998 flood caused more damage, in part because the retention capacity of lakes in the middle and lower Yangtze Valley has shrunk by almost half in the last 50 years due to increased sedimentation (annually the river deposits 426 mt [470 tons] of silt at Wuhan in Hubei Province, close to the center of its middle reach) and because land has been reclaimed for housing and agriculture. Forest cover along the river has also shrunk by half since the 1950s, in no small part the result of Mao Zedong’s Great Leap Forward, when millions of Chinese built wood-fired furnaces to smelt backyard steel in support of the Communist leader’s goal to lead the world in steel production. During this same period, marshland along the river was drained as farmers built houses and planted fields. In 21st Century Science and Technology magazine (Fall 2000, Vol. 13, No. 3), US journalists William C. Jones and Marsha Freeman estimated that if the 1954 flood were to occur today, the damage would increase by a factor of 10. Chinese journalist and dam opponent Dai Qing, who spent almost a month is jail for her views, and other Chinese experts suggest that water levels were lower in 1954 because flow was diverted from the river channel by dike collapses and deliberate breaches following the ancient practice of flooding farmland to protect developed areas downriver. Although rainfall wasn’t substantial, floodwaters caused damage again in 1999 (a separate incident than that of the 1998 river rising), some say because rising water seeped through dikes weakened by previous floods (according to tradition, the government builds the dikes but the farmers are expected to maintain them). Proponents of the Three Gorges Project say a 186-m (610-ft.) poured concrete dam, taller than San Francisco’s Golden Gate Bridge and 2,092 m (1.3 mi.) across constructed in the most eastern of the Three Gorges, 2,092 km (1,300 mi.) west of Shanghai, will protect people and farmland threatened by the Yangtze’s floods. Beginning in October each year, the level of the dam’s 620-km- (385-mi.-) long reservoir (longer than the Grand Canyon and approximately the distance between L.A. and San Francisco), will be gradually raised to 175 m (574 ft.), impounding 27.5 billion m3 (36 billion yd.3) of water, then lowered during January through May to 145 m (476 ft.) to prepare for rainy-season floods. The dam is designed to have a 483-m- (1,585-ft.-) long spillway with 23 bottom outlets and 22 surface sluice gates that will allow a maximum discharge of 102,500 m3 (134,000 yd.3) per second for a hydroelectric capacity of 18,000 MW – 2.715 kW an hour – enough to meet one-ninth of China’s current energy needs. (Venezuela’s Guri Dam, which until the Three Gorges Project is completed is the world’s largest, produces 10,300 MW.) Most important, the Three Gorges Dam will be equipped with what project engineers insist will be silt prevention dikes and silt clearing sluices adequate to a river so filled with sediment that it runs opaquely brown at its surface. The project also includes two five-stage locks that will lift ocean-going ships, which have not previously had access to the upper river, an unprecedented 152 m (500 ft.) and a ship’s elevator for smaller vessels.

    Demolition of part of Wanxian in preparation for flooding of the Three Gorges Reservoir. Note the uncontained mud and debris.The west-to-east course of the Yangtze reflects China’s stairway topography. From its source at 5,700 m (18,700 ft.) in the Tibetan plateau, the river flows east for 6,276 km (3,900 mi.) to sea level at Shanghai, where it deposits 960 billion m3 (1.25 trillion yd.3) of water per year into the China Sea. During the rainy season, when it’s swollen with glacier melt and monsoon precipitation, the Yangtze runs 30 m (100 ft.) higher through the Three Gorges, sometimes rising as much as 18 m (60 ft.) in 24 hours. Reflecting the “staircase” geography through which it flows – dropping 6,614 m (21,700 ft.) from its mountain source – the flooded river is also fast-moving. Records from 1870 have water rushing past the riverbanks at a whopping 110,000 m3 (143,875 yd.3) per second. More recently during a 1970 flood, the river was clocked as running at 2,700 m3 (3,532 yd.3) per second. We experienced some of this when, on our fourth day out, the river began to rise – 12 m (40 ft.) in less than 24 hours – and we were put ashore short of our destination because the engines of our 200-passenger German-built cruise ship were inadequate to push the ship through the escalating current.
    Travel photographs of the Three Gorges suggest the Yangtze’s banks are an uninhabited natural wonderland, but in fact 400 million people live along the river – one-third of China’s total population and one-fifth of the world’s. The Yangtze River Basin produces 50% of China’s cotton and 70% of its grain, and despite a history of disastrous floods, four of China’s 10 largest cities have been built along the riverbanks (Chongqing, headquarters for Chiang Kai-shek’s nationalist government during World War II; Wuhan, an industrial city in the middle of the cotton growing region where we began our cruise; Nanjing, which anchors China’s richest and most populous area, the Land of Fish and Rice along the river’s lower reach; and the port city of Shanghai – each with a population of more than 8 million). We boarded our ship in an area of the old international concession protected by levees meant to accommodate a 7.6- to 9.0-m (25- to 30-ft.) rise in river level. The guide told me that in the 1998 flood, these levees had to be augmented with sandbags, and another guide in a local geology museum told me how floodwaters in the museum’s garden rose above his waist. And although the well-maintained hotels and businesses on the land side of the levees looked secure, less affluent Wuhan residents were living along the riverbank inside the embankments.
    Slough of streambank into the river, west of Wuhan, in the area where streambank erosion is caused in part by boat wash.In total, the Yangtze drains 1.8 million km2 (695,000 mi.2), roughly 18% of China’s landmass, but it is here in the river’s middle reach, east and west of our embarkation point, where the battle against water has been fought for centuries. Here the Yangtze runs 1.6-2.1 km (1.0-1.3 mi.) wide through a flat, low-lying landscape, its bed so thick with silt that it’s called the Hanging River. During flood season the water level can rise 6-17 m (20-56 ft.) above the river’s floodplain on both its banks, and some residents are said to live 3-7 m (10-23 ft.) below water level. It was here in the middle reach during the Ming Dynasty (1368-1644) and then later in the Qing (1644-1911) that funds from the imperial treasury were allocated to build dikes as high as 10-16 m (33-53 ft.) to prevent flooding on the river’s north bank. Here the mighty river slows down, meandering and looping and depositing so much silt that its raised bed requires constant dredging; here the navigation channel crosses from one side of the river to the other to avoid built-up silt, and the wash from hundreds of barges and tugs and cruise ships causes mini landslides on either side of the Yangtze’s banks. We saw this for ourselves on the first day out of Wuhan as garbage can-size chunks of thick red soil sloughed into the water in our ship’s wake.
    A section of spillway on the Three Gorges Dam

    Family living inside the leveeHere where cotton and grain grow on the rich alluvial Jianghan Plain, flooding has traditionally been dealt with by building levees, the effectiveness of which has just as traditionally been compromised by lack of maintenance and the fact that sediment deposits continue to raise the river level. To remedy the situation, the Jingjiang Flood Diversion Project was launched in the 1950s, which included strengthening 180 km (112 mi.) of dikes along the river’s north bank and construction of flood-intake sluices and regulating dams and retention basins on the south. The efficiency of the south bank basins has gradually diminished, however, as millions of Chinese have settled there to live and farm (estimates are that as many as 5 million people live in retention areas). On our first day on the river, with its flow already swollen from rainy season storms, we saw open sluice gates that funneled river water into what looked like irrigation ditches and then at a distance across the flat floodplain what looked to be armored levees about the height of those we’d seen in Wuhan. Along this wide stretch of the river, sections of the south bank were alternately unprotected or armored with cemented rocks and boulders or newer looking soil-filled concrete hexagons. We saw 3- to 5-km (2- to 3-mi.) stretches where symmetrical double and sometimes triple rows of poplar trees were planted in front of the newer armored banks, many of the trees standing in water a quarter of the way up their trunks. (The Chinese government seems to have adopted trees as an environmental catch-all; in Beijing a guide explained that the government encouraged planting trees as a remedy to the city’s chronic air pollution.) When I asked our river guide why one stretch of bank was left natural and an adjacent section armored, he told me the armored sections were “infected with an organism,” which he couldn’t describe or name but that made the soil more susceptible to erosion. The area we passed through on those first two days of our voyage was alternatively agricultural and developed with light industry, and in places where factories and/or housing had been built close to the river, elaborate brick or what looked like concrete block levees had been constructed. In contrast, upriver in the Three Gorges, where the riverbanks were higher and much steeper, towns were built directly on the water with no flood control protection, and local guides told of frequent washouts. Agriculture was much in evidence in the Three Gorges and farther west, despite the fact that much of the land slopes 45º or more. What we saw close to the river were mostly small hillside plots of corn, wheat, potatoes, and small orange and nut orchards, some crops planted in rows running perpendicular to the river, a practice that is now illegal. In other places, the slopes had been roughly terraced with stones. Throughout the Three Gorges and beyond, there was evidence of massive deforestation, with only an occasional stand of evergreens suggesting the vegetation that had once covered these hillsides. Occasionally we saw signs that exhorted farmers to return their farms to forests, part of a multiyear program the government initiated in the late 1990s. But when I asked the river guide if the government compensated farmers for taking land out of cultivation or supplied them tree stock to plant, he just smiled – although he did mention the government had repeatedly seeded this area by air. In the three rainy days we spent on the river, we saw water running uninhibited off hillsides from tributary streams, from road cuts high in the limestone cliffs, off farmland that had been abandoned in anticipation of flooding from the dam and off riverside cuts where gravel had apparently been mined or soil removed, perhaps for terracing. Later as we were bused through the countryside from Fengdu (a city that is to be flooded under the Three Gorges Reservoir) to Chongqing, we saw first-hand where runoff originates. Rice was being grown on steep, terraced hillsides where exposed soil was running off uninhibited toward the river 0.8-4.8 km (0.5-3.0 mi.) below us. Small earthen detention basins had been constructed in places, but after three days of rain, they were overflowing. Many of the roads were dirt paths, and water and soil ran off them freely. In one small town, an apartment or office building was being constructed on a steep hillside, and water poured off the hill above the unfinished building and through its unenclosed doors and windows as if over a dam. Closer to Chongqing, a long cut had been made in a loamy 61-m- (200-ft.-) high cliff to widen an existing highway. With no sandbags, silt fencing, or hay bales to contain it, soil was pouring off the cut and onto the paved section of the highway, to eventually find its way to the river. All this seems to point to the fact that although the Three Gorges Dam might impound dangerously high floodwater, unless something is done about controlling upriver erosion, high sediment levels will continue to the threaten the river. As reported by the government newspaper, People’s Daily, on July 30, 2000, 40% of the Yangtze River Basin – some 740,000 km2 (285,714 mi.2) – experiences erosion, and every year the basin loses 2.03 billion mt (2.24 billion tons) of soil, damaging 67,000 ha (165,560 ac.) of cultivatable land.

    Entering the middle of the Three GorgesThe possibility of major silt buildup has been voiced as a concern among opponents of the Three Gorges Project, who suggest sediment will pile up behind the dam and render it useless for generating electricity, as occurred with the Sanmenxia Dam built on the Yellow River in the 1950s. Reports are that a $14 million World Bank study concluded silt carried downriver and deposited in the dam’s reservoir could alter the course of the Yangtze, which could actually increase the risk of flooding in bad years. In the end, the World Bank refused to finance the project, maintaining that the era of big dams has come to an end. In response, project engineers point to the Gezhouba Dam, built in the 1980s 44 km (27 mi.) downriver from the Three Gorges Project, a 70-m- (230-ft.-) high low-water dam that was constructed with silt prevention dikes and silt-clearing sluices and is still functioning and producing electricity. Given that water in the Three Gorges Reservoir will slow and no longer flush large amounts of sediment downstream, Chinese experts predict that in as little as 80 years, silt could build up in this stretch of the tamed river, causing the bed to rise and making the river once again unnavigable for large ships. Chinese and international environmentalists also complain that flood control is coming at a high price, that the dam will destroy habitat for the Chinese alligator, white crane, the river dolphin (on which Chinese fishermen have depended for centuries) and the prehistoric Chinese sturgeon, unique to the river. And although the dam is supposed to protect 400 million people from downstream flooding, some million and a half people in the Three Gorges region will have to be relocated, in many cases to less productive land, as farms and towns are flooded. Both Chinese and international experts repeatedly have suggested that a better plan would be to dam the Yangtze’s upriver tributaries, controlling the water’s flow before it joins the main stream, and then implement massive upriver reforestation and sound erosion control practices throughout the countryside.At 9:48 a.m. on November 6, 2002, eight months ahead of the official schedule, the diversion channel through which the Yangtze River has flowed for the past three years was closed off and water began backing up behind the completed north-bank segments of the Three Gorges Dam. Construction of the final segment of the dam and its two power houses is scheduled for completion in 2009, when the project will begin generating at full capacity, justifying its $30 billion investment.