Dams and Impounded Rivers - River Dynamics and Integrated River Management - page 426

7.3.1.3 Infant Life
Dam failures occur at various ages. The dam failure events are grouped according to the age of failed
dams into 0-1, 1-5, 6-10, 11-20, 21-30, 31-40, 41-50, 51-60, 61-70, 71-80, 81-90, 91-100, 100-200,
and >200 years. Figure 7.26 shows the percentages of different age groups of failures of large dams
(higher than 15 m) in China and throughout the world. The data on dam failures in China were collected
in the period 1954-2003, and the data on other countries are from 50 countries including the U.S., UK,
Australia, and India, including 900 dam failure events. About 60% of dam failures in China occurred within
one year, in other words, the dams failed during the first flood or in the first time to impound water. A
great many of these dams were constructed during the “Great leap” period in 1957-1962, a particular period
in Chinese history of paying attention only to quantity but not quality. In the figure, the data on the world
dam failures are collected from selected countries.
Fig. 7.26 Percentages of dam failures for different age groups in China and other countries
Similarly, Fig. 7.27 shows the percentage of different age groups of dam failures in Russia in comparison
with the failures of world dams (He et al., 2008). The figures show that the dam failures mostly occur for the
dams younger than 10 years. The dam failure probability reduces rapidly following with operation time.
Fig. 7.27 Percentage of different age groups of dam failures in Russia in comparison with the failures of world dams
Many dam failures occur in arid and semi-arid areas. Figure 7.28 shows the spatial distribution of the
dam failure rate in China, which was based on statistics of dam failure events in the provinces, in which
the dam failure rate in each province is shown (He et al., 2008). The number in the figure is the failure
rate × 10 4 . The dam failure rate is zero in Tibet, because there were no dams in the area. High dam failure
rates occur in the north-west China, where the annual precipitation is low and rainfall intensity in summer
is high. The figure shows a division line between provinces having a high dam failure rate (>15×10 4 ) and
a low dam failure rate (<15×10 4 ), and also a contour of 400 mm precipitation. The division line and the