In this paper I summarize the results of a worldwide study of 167 dams that have been constructed on preexisting landslides. Many major landslides in the past have blocked, or partially blocked, river valleys, providing possible dam sites that at first sight have appeared to be ideal. Thus, dams were occasionally built on landslides without a complete understanding of the problems involved. Today, however, every effort is made in the selection of dam sites to use foundations and abutments that are generally impervious and capable of withstanding the stresses imposed by the proposed dam and reservoir under all probable loading conditions. Any pre-existing landslides that might impinge on the foundation or abutments of a dam should be carefully investigated. If a landslide is recognized in a dam foundation or abutment, the landslide deposits commonly are avoided in siting the dam or are removed during stripping of the dam foundation and abutment contacts. However, it has often been found to be technically feasible and economically desirable to site and construct dams on known landslides or on the remnants of these features. In these cases, proven preventive and/or remedial measures have been used to ensure the stability of the foundations and abutments, and to reduce seepage to acceptable levels.
"No structure grips the ground so closely as a dam. It holds on at its base and at its flanks… In other words, a dam is made up of two parts: the artificial dam, man-made, and the natural dam, which continues it, surrounds it, and on which it is founded. From Coyne's statement it can be further inferred that any movement, or potential movement, of the foundation or an abutment2 is critical to the stability and effectiveness of the dam itself.