In this volume, the erosion and conservation measures discussed are, for the most part, those under unirrigated agriculture. The use of irrigation could cause significant changes in the growing seasons, and in the agricultural calendar, especially in the warmer climates where temperature is not a limiting factor. It is further noted that much of the material in this volume has been prepared with the developing countries of the so-called Third World in mind. In many of these countries there is a dearth of basic data, such as long-term hydrological records, detailed soil and topographic surveys, and experimental results for various types of erosion control measures. Some design procedures cannot be imitated or copied directly from those of the technologically more advanced countries. Consequently, emphasis will be placed, wherever possible, upon simple empirical methods of design, and approximate solutions within the limitations of the available data, technical possibilities, and financial resources of the Third World countries. Much of the numerical data and calculations will be presented in the metric system.