Debris Flows and Landslides - River Dynamics and Integrated River Management - page 195

4.1.3 Landslide Disasters
4.1.3.1 Landslide Events
More than 30 large-scale landslides occurred along the Sichuan-Tibet Highway in the 1960s. The landslides
blocked the highway more than 1,500 days. A landslide damming the Palongzangbu River created the
Ranwu Lake, at 3,990 m above the sea level, it is 26 km long and 1-2 km wide. A landslide at the Layue
section of the highway in 1966 with a sliding volume of over 20 million m 3 destroyed 5 km highway and
the highway route had to be changed. From June to August 1966, 648 landslides occurred in the Guxiang
Gully in Tibet Autonomous Region and provided abundant solid material for large-scale debris flows.
Dongjiu Village is located by the Lulang River and the Sichuan-Tibet Highway. A heavy rainstorm
triggered a landslide in September 1991. The sliding body thrust into and dammed the Lulang River. The
river water was forced to scour the highway destroying it (NFH and IMH, 1994).
In the Three-Gorges area of the Yangtze River evidence of 404 landslides and avalanches has been
observed with a total volume of 3 billion m 3 , which dammed the river and stopped navigation in the
channel many times. Figure 4.6 shows the distribution of large-scale landslides and rock avalanches along
the Yangtze River near the Three Gorges Dam. Many villages and towns are located in the old landslide
areas or even on the sliding bodies. Landslides threaten the people there. Most of the landslides are
bedrock landslides occurring in strata of classic rocks with weak intercalation. There are a few landslides
in surface deposits. They were partly or completely revived old landslides in bedrock. The Liyutuo landslide
is located in Wushan County, on the left bank of the Yangtze River, as shown in Fig. 4.6. The volume of
its remains is about 10 million m 3 . In September 1979, a rainfall that lasted for more than 10 days triggered
superficial landslides on the front part of the landslide deposit with a volume of 0.78 million m 3 . Soon
afterwards, several open cracks appeared near the rear margin and the east lateral border of the old
landslide deposit (SCST and MGMR, 1988).
Fig. 4.6 Distribution of large-scale landslides and rock avalanches along the reaches of the Yangtze River upstream
of the Three Gorges Dam
The Xintan landslide occurred in 1985. It was a large-scale landslide that attracted attention from the
whole country. Figure 4.7 shows the sliding body of the Xintan Landslide before and after sliding. The
town of Xintan was located on the left side of the Yangtze River in Xiling Gorge, about 37 km upstream
from the Three Gorges Dam site. At 3:45 on June 12, 1985 a sliding body 50 m thick, 2,000 m long and
200-700 m wide with the town of Xintan on it collapsed and slid into the Yangtze River. The total
volume of the sliding body was 30 million m 3 and more than 2 million m 3 thrust into the river. The Town