Landslide Dams : Processes, Risk, and Mitigation

Landslide dams have proved to be both interesting natural phenomena and significant hazards in many areas of the world. A few of these blockages attain heights and volumes that rival or exceed the world’s largest man-made dams. Because landslide dams are natural phenomena, they are vulnerable to failure by overtopping and breaching. Some of the world’s largest and most catastrophic floods have occurred because of failure of these natural dams. In the United States, hazards related to landslide damming have received special attention in the past decade as a result of the 1980 blockage of the North Fork Toutle River in the State of Washington by the debris avalanche associated with the eruption of Mount St. Helens, and the 1983 damming of the Spanish Fork River in central Utah by the Thistle landslide. In each of these cases, the possibility of failure has been mitigated by construction of outlet structures that have either controlled the reservoir level or drained the reservoir. This volume, conceived in response to the above cases, consists of nine papers on landslide dams. The first paper deals with the landslide processes involved in forming these natural dams, the potential for catastrophic failure of the dams, and upstream and downstream effects of the dams. The other eight papers are case histories from the United States, Canada, Pakistan, Japan, and China that discuss the processes, risks, and mitigative measures involved in landslide damming.