The present state of the art of dam engineering has been ronmental, and political factors, which, though important, attained by a continuous search for new ideas and methods are covered in other publications. while incorporating the lessons of the past. In the last 20 The rapid progress in recent times has resulted from the years particularly there have been major innovations, due combined efforts of engineers and associated scientists, as largely to a concerted effort to blend the best of theory and exemplified by the authorities who have contributed to this practice. Accompanying these achievements, there has been book. These individuals have brought extensive knowledge a significant trend toward free interchange among the pro to the task, drawn from experience throughout the world. fessional disciplines, including open discussion of prob With the convergence of such distinguished talent, the op lems and their solutions. The inseparable relationships of portunity for accomplishment was substantial. I gratefully hydrology, geology, and seismology to engineering have acknowledge the generous cooperation of these writers, and been increasingly recognized in this field, where progress am indebted also to other persons and organizations that is founded on interdisciplinary cooperation. have allowed reference to their publications; and I have This book presents advances in dam engineering that attempted to acknowledge this obligation in the sections have been achieved in recent years or are under way. At where the material is used. These courtesies are deeply ap tention is given to practical aspects of design, construction, preciated.

Most dam accidents with hydroelectric plants are due to under-dimensioning of the maximum floods of spillway design, causing extravasation and dam breaks (this occurs in 23% of the accidents). This work highlights the relationship between spillway design and potential dam failure and other important aspects of these structures and presents the methodology of design based on the international experience on the subject. The book covers river basin studies and floods (the geology, geomorphology, hydrology, hydraulics, and layouts of the works). Further, spillway function, capacity and design flood, layouts, or arrangements, of hydroelectric works and types of spillways are treated in the book. Finally, the book discusses examples of dams that broke due to insufficient spillway capacity. The book is intended for engineers and the companies that design dams and power plants around the world, as well as students in dam and hydraulic engineering. In short, people interested in producing electricity that is clean and potentially cheaper than other sources.

Although hundreds of stilling basins and energy­dissipating devices have been designed in conjunction with spillways, outlet works, and canal structures, it is often necessary to make model studies of individual structures to be certain that these will operate as anticipated. The reason for these repetitive tests is that a factor of uncertainty exists regarding the overall performance characteristics of energy dissipators. The many laboratory studies made on individual structures over a period of years have been made by different personnel, for different groups of designers, each structure having different allowable design limitations. Since no two structures were exactly alike, attempts to generalize the assembled data resulted in sketchy and, at times, inconsistent results having only vague connecting links. Extensive library research into the works of others revealed the fact that the necessary correlation factors are nonexistent. To fill the need for up-to-date hydraulic design information on stilling basins and energy dissipators, a research program on this general subject was begun with a study of the hydraulic jump, observing all phases as it occurs in open channel flow. With a broader understanding of this phenomenon it was then possible to proceed to the more practical aspects of stilling basin design. This monograph generalizes the design of stilling basins, energy dissipators of several kinds and associated appurtenances. General design rules are presented so that the necessary dimensions for a particular structure may be easily and quickly determined, and the selected values checked by others without the need for exceptional judgment or extensive previous experience. Proper use of the material in this monograph will eliminate the need for hydraulic model tests on many individual structures, particularly the smaller ones. Designs of structures obtained by following the recommendations presented here will be conservative in that they will provide a desirable factor of safety. However, model studies will still prove beneficial to reduce structure sizes further, to account for nonsymmetrical conditions of approach or getaway, or to evaluate other unusual conditions not described herein.