Tsao-ling rockslides, Taiwan

On the mountainous island of Taiwan, where earthquakes and typhoons are common, many landslide disasters occur. The Tsao-Ling rockslides are perhaps the bestknown landslides in Taiwan. Between 1862 and 1979, four large catastrophic rockslides occurred on the southwest slope of Mount Tsao-Ling. These multimillion cubic meter mass movements created substantial landslide dams on the Ching-Shui River, which flows at the toe of the Tsao-Ling slope. The failures of these landslide dams resulted in additional catastrophes, which, in three cases, occurred years after the rockslide event. On December 17,1941, a rockslide involving a mass movement of more than 80 × 10 ⁶ m ³ occurred on the dip slope forming the southwest flank of Mount Tsao-Ling, triggered by a strong earthquake. On August 10,1942, heavy rain caused another rockslide on the same slope, and more than 100 × 10 ⁶ m ³ of rock slid down the Tsao-Ling dip slope. The Ching-Shui River was dammed with rock debris. The landslide dam (140-200 m high, 4800 m wide at base) was overtopped on May 18, 1951 and 120 × 10 ⁶ m ³ of impounded water was suddenly released. More than 100 human lives were lost. On August 15, 1979, heavy rain caused a breakaway failure from the lower part of the remaining slope. The slide mass collided with the original debris dam and the Ching-Shui River was once again dammed. The landslide dam was overtopped on August 24,1979. From 1980 to 1993, intensive investigations in the greater Tsao-Ling area were undertaken. We conclude that a further rockslide involving a mass movement of 50 × 10 ⁶ m ³ or so is possible.