Jo Johannis Dronkers

Jo Johannis Dronkers (24 May 1910 – 20 February 1973) was a Dutch mathematician who is notable for the development of mathematical methods for the calculation of tides and tidal currents in estuaries. His work formed much of the mathematical basis for the design of the Delta Works.

Education and early work

Jo Johannis Dronkers was born in Poortvliet, the son of Willem Dronkers, a mayor, and Cornelia Pieternella van der Slikke. He had a twin brother, Johannis Jo Dronkers (1910-1993). He attended the State High School in Bergen op Zoom and then studied mathematics and physics at Leiden University. He completed his dissertation entitled "On stratifiable congruences" in 1939 under the supervision of Professor Willem van der Woude.

Although his work dealt with a problem in pure mathematics, it was notable for containing eleven propositions, five of which concerned tides. Three of these five propositions contained fundamental criticism of the work of Jannis Pieter Mazure, who at that time was one of the most influential people in the field of tidal calculations in the Netherlands. Another of Dronkers' propositions concerned an inaccuracy in the work of Hendrik Lorentz contained in Lorentz's report on tidal movements as a consequence of the Zuiderzee Works.

Rijkswaterstaat and the Delta Works

In 1934, Dronkers joined Rijkswaterstaat, where he was placed in the Sea Arms, Lower Rivers and Coasts service, a section of the Directorate Lower Rivers under the leadership of Dr. Johan van Veen. Dronkers was charged with undertaking a detailed mathematical study of tides and related issues. He was actively involved in the reclamation works which followed the Inundation of Walcheren in 1945, and is portrayed as "The Calculator" in the non-fiction novel Het verjaagde water by A. den Doolaard.

Dronkers published research and technical papers on hydraulic engineering subjects including tidal basin closures, in collaboration with engineers such as Frank Spaargaren. He also played an important role in advanced studies and design work for the Delta Works after the North Sea Flood of 1953. In 1963, he became head of the hydrological department of the Delta Service, succeeding Ir. H.A. Ferguson. He made significant contributions to the tidal calculations required for the Delta Works.

Dronkers' mathematical contributions were pivotal in advancing the development of numerous computational methodologies which replaced empirical principles with a more robust scientific foundation, transforming the domain of hydraulic engineering. They enabled the anticipatory analysis of the impacts of hydraulic interventions, thus facilitating the formulation of evidence-based strategies in this field.

Dronkers' seminal work, "Tidal computations in rivers and coastal waters" (1964), remains a benchmark in the domain of tidal calculation theory. However, its creation was not without controversy. Dronkers' computational approach, though rigorous, was criticized by Van Veen for its complexity and computational demands, which he believed could hinder timely practical applications. Instead, Van Veen proposed the use of an electrical analogue. Conversely, the notable Dutch civil engineer Johannes Theodoor Thijsse advocated for a physical model-based approach.