Book excerpt: This book treats the subject of local scour around different kinds of marine structures, exposed to waves and/or currents. The first, major part of the book is devoted to marine pipelines, describing in detail all kinds of scour scenarios, and also making recommendations for scour protection. Other kinds of structures considered are single piles (slender or large), groups of piles, complex subsea structures, breakwaters, and seawalls. The scour due to ship propellers is also described. The book deals mainly with the scour in noncohesive sediment but, whenever possible, available literature on the scour in finer sediment has been incorporated. In addition, a chapter on the impact of wave-induced liquefaction is included.The authors' aim is to describe in detail the hydrodynamic processes causing the erosion. With a hydrodynamic understanding, it is easier for the consulting engineer to predict scour in those many cases where physical model tests are not available.