Tidal calculations in the Netherlands, 1920-60

The computing problems in the field of tidal calculations in the Netherlands between 1920 and 1960 are described. These calculations were necessary to predict the changes in the water movements caused by hydraulic works like the Zuiderzee Works and the Delta Works. The growth of computing problems in this field was caused not only by the increasing technical complexity of the hydraulic works, but also by the growing importance of the tidal calculations in the decision process. Before the introduction of the digital computer. several solutions were developed and used: numerical methods, analog electrical machines, and large-scale models. The required accuracy of the predictions and the number of alternative plans for which calculations had to be done were important factors in the choice between the alternative methods.<>