The first International Conference on Hydraulic Design in Water Resources Engineering held at Southampton University in 1984 brought together engineers interested in channels and channel control structures. It was well attended, very successful and generated papers relating to control and diversion structures, sediment control facilities for headworks and intakes, canals under quasi-steady flow conditions, computer simulation of irrigation and drainage canal systems under unsteady flow conditions, and sediment problems in rivers and the effects of engineering works on the regime of rivers. The success of the first meeting was a major factor in deciding to reconvene the Conference in April 1986, also at Southampton University. The second conference is concerned with the design, constructions and operation of land drainage systems and the wealth of papers received for presentation is an indication of how much this subject has developed in the last few decades. The Conference is intended to bring together as much information as possible in the field of Land Drainage together with forecasts of future developments in this important subject. The Proceedings will provide a unique reference and state-of-the-art presentation to all interested in Land Drainage. The Proceedings incorporate the text of a keynote lecture given by W. H. van der Molen, an eminent researcher. His participation added to the prestige of the Conference and the Editors would like to thank him most sincerely for his contribution.

The development of water resources has proceeded at an amazing speed around the world in the last few decades. The hydraulic engineer has played his part: in constructing much larger artificial channels than ever before, larger and more sophisticated control structures, and systems of irrigation, drainage and water supply channels in which the flow by its nature is complex and unsteady requiring computer-based techniques at both the design and operation stage. It seemed appropriate to look briefly at some of the developments in hydraulic design resulting from this situation. Hence the idea of the Conference was formed. The Proceedings of the Conference show that hydraulic engineers have been able to acquire a very substantial base of design capability from the experience of the period referred to. The most outstanding development to have occurred is in the combination of physical and mathematical modelling, which in hydraulic engineering has followed a parallel path to that in other branches of engineering science. The Proceedings of this Conference will give to the reader an awareness of the current state of hydraulic design in open channel flow and open channel control structures. K.V.H. Smith Editor 1. CONTROL AND DIVERSION STRUCTURES 1-3 FACTORS AFFECTING BRINK DEPTH IN RECTANGULAR OVERFALLS G.C. Christodoulou, G.C. Noutsopoulos and S.A. Andreou Dept. of Civil Engineering, National Technical Univ. of Athens, Greece.