Design and performance of materials for subsurface drainage systems in agriculture

During the second half of the 20th century, numerous land drainage systems using new materials for the drain channels that often function inadequately due to biochemical and mechanical clogging, were developed. The design of drainpipes and envelope materials used for these land drainage systems was based on both theoretical and experimental investigations. This contribution reviews the simultaneous development of theory and practical experience in Europe and North America. The results of the effect of perforation shape and pattern in drainpipes and of envelope materials on drainage performance are summarized and the latest design criteria of granular materials and synthetic envelopes presented. Theoretical investigations are associated with field data on the performance of drainage materials. A thorough knowledge, not only of the flow conditions, but also of the physical soil properties in the vicinity of the drains is imperative for a correct interpretation of field data. This contribution represents the main features on drainpipes and envelope materials, and the physical soil processes that occur in the vicinity of the drain. It gives an overview of the research work done referring to numerous publications where relevant and detailed information can be found.