The Waterloopkundig Laboratorium (Hydraulic Research Laboratory) was an independent Dutch scientific institute specialising in hydraulics and hydraulic engineering. The laboratory was established in Delft from 1927, moving to a new location in the city in 1973. The institute later became known as WL | Delft Hydraulics. In 2008, the laboratory was incorporated into the international nonprofit Deltares institute.
Purpose The Hydraulic Laboratory was classified by the Dutch Government as a major technological institute and was tasked with acquiring, generating, and disseminating knowledge on hydraulics and hydraulic engineering. The laboratory conducted research into the causes of changes in the course of rivers, estuaries, and coasts, and the possible influences on them due to hydraulic engineering activities, along with a range of studies on topics such as dredging, wave action and coastal morphodynamics. The laboratory played a significant advisory role in the conception, design, and implementation of the Zuiderzee Works and the Delta Works, along with several international projects.
History The laboratory was established in 1927 by Rijkswaterstaat, under the directorship of Professor ir. J.Th. Thijsse (1893–1984). It was initially located in the basement of the Civil Engineering Department building at Delft University of Technology. Thijsse's role on the Zuiderzee State Commission had introduced him to hydrodynamic model research, an innovative approach to understanding the dynamics of water. In 1927, both Rijkswaterstaat and Delft University of Technology began incorporating this research methodology, prompting the establishment of the laboratory. The impetus for the formation of the laboratory began in the 1920s, and lay in the design of the sluices for the Afsluitdijk, a significant project requiring extensive research and experimentation. The task was initially assigned to Professor Theodor Rehbock at the Flussbaulaboratorium (river construction laboratory) at the Technical University of Karlsruhe, a major institute in the field of hydraulic engineering research at the time. The results of this investigation were documented in a report which was published in 1931. This report was subject to review by Thijsse, who advised the Dutch authorities on the need for additional research of this type, not just for the Zuiderzee Works, but also for other projects across the Netherlands. This recommendation precipitated the decision to establish a laboratory similar to that in Karlsruhe, to serve the Netherlands. Thijsse spearheaded the initial research at the newly formed laboratory and documented the findings in a follow-up report to Rehbock's original study. To facilitate third-party contract research, such as work for Rijkswaterstaat and international schemes, it was decided that the laboratory would operate independently from the Delft University of Technology, and be established as a financially autonomous foundation, with its board appointed from university staff, major consultants, and representatives from Rijkswaterstaat. Experiments into the behaviour of irregular waves had been undertaken in the Netherlands since 1920, with initial experiments on irregular wave behaviour in wind tunnels. This pioneering research, including investigations into wave run-up, led to the construction of a specialised wind wave flume at the laboratory in 1933. Unprecedented at the time of construction, the flume boasted dimensions of 25 metres in length, 4 metres in width, and a maximum water depth of 0.45 metres. Subsequently, in order to better satisfy the necessary conditions for wave height and period, the flume was extended to 50 metres in length, and fitted with a monochromatic wave generator. These enhancements enabled a wider variety of research projects, including studies on wave overtopping, the stability of rubble-mound breakwaters, wave impact forces, and the stability of floating structures. By the time of World War II, research had extended into model investigations of wave generation, with outcomes corroborating prototype data collected by Harald Sverdrup and Walter Munk. In 1969, new wave flumes with typical widths of 8 metres were installed in the laboratory in order to permit modelling and testing of breakwaters and dikes whilst simulating arbitrary angles of wave attack. The previously available flume widths of 4 metres had proved too small for this purpose, and the new flumes therefore provided the laboratory with the ability to model and test the performance of significant coastal and river engineering structures. In 1973, the laboratory moved from its location in the centre of Delft to a new location at the most southern end of the Delft Technological University campus, becoming known locally as the Thijsse-erf (Thijsse yard). Throughout its history, the laboratory undertook national and international research on numerous civil and hydraulic engineering subjects including dredging technology, density issues, pumps, and detailed structural studies on locks and weirs. International projects included the Belgian Port of Zeebrugge (1933–36), the cut-off of the Abidjan lagoon (1933–46), and flood prevention works in Nottingham (1946–51).
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