"Strong, Invincible Arguments?" Tidal Models as Management Instruments in Twentieth-Century Dutch Coastal Engineering

In the twentieth century Dutch hydraulic engineers developed different types of models for tidal calculations, including numerical, electrical and hydraulic ones. These models aimed specifically to predict the propagation of tides at sea into bays and estuaries and up tidal rivers. The aim was to predict the effects of projected hydraulic works-which were becoming ever more ambitious-on tidal levels and currents at inshore locations. We argue that these models were not motivated primarily by technical considerations but rather by the engineers' need to manage the network of stakeholders around their hydraulic projects. As the scale and risk of projects increased in the course of the century, engineers' ability to mobilize support depended increasingly on establishing public trust in their tidal propagation models. Early models developed for the Zuider Zee only had to assuage fears about the effects of an established plan; they could be slow and laborious. In the Delta region in the1930s where different hydraulic/political options had to be investigated, rapidity, flexibility and accuracy all became important. In this phase the management potential of the models became their most salient feature.