Erosion is the most common cause of failures at earth-dams, dikes and levees, whether through overtopping and overflowing, or internal erosion and piping. The present work is dedicated to the phenomenon of internal erosion and piping. It is not intended to be exhaustive on the subject, but brings together some of the latest international research and advances. Emphasis is on physical processes, how they can be studied in the laboratory, and how test results can be applied to levees and dams. This work covers the results from several research projects in Australia, France, the Netherlands, and the United States. Our aim has been to share our most recent findings with students, researchers and practitioners. Understanding the failure of an earth-dam or a levee by erosion in a unified framework, be it internal erosion or surface erosion, requires continuous research in this field. We hope that the reader gains knowledge from this book that leads to further progress in the challenging field of the safety of levees and dams.