Ramón Iribarren Cavanilles

Ramón Iribarren Cavanilles Ing.D (15 April 1900 – 21 February 1967) was a Spanish civil engineer and professor of ports at the School of Civil Engineering (, ETSICCP) in Madrid. He was chairman of the Spanish delegation to the Permanent International Association of Navigation Congresses and was elected as an academic at the Spanish Royal Academy of Sciences, although he did not take up the latter position. He made notable contributions in the field of coastal engineering, including methods for the calculation of breakwater stability and research which led to the development of the Iribarren number.

He undertook detailed research at several ports in the Bay of Biscay which were subject to extreme waves and frequent storms, and this underpinned much of his early research work. Iribarren recognised that many of the ports in the Bay of Biscay were insufficiently protected from severe wave and storm conditions, which had resulted in a number of shipwrecks and threatened the economic viability of the local fishing community, with whom he enjoyed a close relationship.

He was instrumental in the development of a research facility for coastal engineering, the first of its kind in Spain. and remains highly relevant, being subject to ongoing development and underpinning several contemporary design methods used in coastal engineering and coastal protection works.

Life and career Education and early work Iribarren was born in Irún in 1900, the son of Plácido José Iribarren Aldaz, a wealthy businessman with properties in Cuba, and Teresa Cavanilles Sanz. The eldest of three brothers, he initially studied at the school in his hometown, where he excelled as a student of mathematics. Upon graduation, he initially worked for the Ministry of Public Works at the regional Catalonian roads department in Girona.

Iribarren undertook extensive research at the Port of Mutriku, where he was responsible for the design and construction of a breakwater to the outer harbour in 1932. The works mitigated the approach and entry difficulties for shipping at the outer harbour area, but Iribarren observed that the existing vertical sea walls of the inner harbour were still causing significant wave reflection, leading to dangerous berthing conditions for ships once inside the mouth of the harbour. Despite initial opposition from the local fishing community, he was successful in implementing a sloping breakwater at the inner harbour in 1936, which ended the problems caused by reflection and made safe berthing of ships possible.

The work at Mutriku provided Iribarren with the opportunity to develop his fundamental theories around refraction, allowing him the time and environment in which to research and observe his theoretical approximations of wave direction and wave characteristics from available depth contours. He published papers on his work at Mutriku in 1932 and 1936, and this work led to the development of a dimensionless parameter for waves breaking on a slope, which was further developed by Jurjen Battjes in 1974

The importance of this parameter for so many aspects of waves breaking on slopes appears to justify that it be given a special name. In the author's opinion it is appropriate to call it the "Iribarren number" (denoted by "Ir"), in honor of the man who introduced it and who has made many other valuable contributions to our knowledge of water waves. — Jurjen A. Battjes title="Surf Similarity" — Proceedings of the 14th International Conference on Coastal Engineering (1974)

Meanwhile, Iribarren was approached by the French authorities to prepare a design for similar works across the river in the town of Hendaye. The project was a major success and in 1949, seeing the results of Iribarren's work in Hendaye, the City Council in Hondarribia approved the construction of a breakwater to his design. Iribarren supervised construction which commenced on 7 September 1949, with the works completed in 1955 at a cost of 18 million pesetas. He made changes through an iterative design process as construction progressed, with the final breakwater being 1,100 metres in length, 40 metres wide at the base and using 300,000 tonnes of armourstone from a quarry in Jaizkibel. The project was a success, solving the erosion problems, increasing navigation safety and creating a large recreational beach. Iribarren promoted the idea of establishing a Spanish centre for the study of coastal engineering and harbour works, modelled on research facilities in universities such as Technische Universität Berlin and ETH Zurich. This was achieved in 1948 with the creation of the Ports Laboratory in Madrid, with Iribarren as Director. In 1957 the laboratory became part of the Centro de Estudios y Experimentación de Obras Públicas.

The Port of Palma de Mallorca and the Wave Diagram Method Iribarren's approach to the study of wave behaviour for the works at the outer breakwater of the Port of Palma de Mallorca was used as the basis for several harbour projects across Spain after he published his or (wave diagram method / method of wave plans) in 1941. Portuguese Iribarren noted that the orientation of the Port of Palma meant that it would only be exposed to storms whose direction varied from Southwest to Southeast. He therefore studied these two extreme storms and their midpoint (the south), and designed the breakwater accordingly.

He used as a starting point the existing theory of trochoidal waves, assuming circular orbital motion for liquid molecules in a body of water agitated by swell at infinite depth, and elliptical motion for those at reduced depths. Iribarren took into account shoaling, and the modifications which waves undergo approaching the coast as they enter shallow water, which he defined as a point where water depth is equal to or less than half the original wavelength.

Iribarren's formula for the design of breakwaters

in which:

is the weight of the armourstone; is the slope of the armourstone (or, more precisely, the cosine of the angle the slope makes with the horizontal when the sine is taken as unity); is the density of the stone relative to that of water, and; is the wave height.

De Castro's formula implies that for , should be zero; which means that when the slope is almost horizontal, even very light armour units can be used.

If is less than , has an imaginary value, indicating that for very steep slopes, a breakwater or dike cannot be successfully constructed no matter how large the armourstone is. If is given a negative value, which is unacceptable, it results in an inadmissible value for .

With de Castro Pascual's encouragement, However, the political situation in Spain and international attitudes to scientific co-operation with the Franco dictatorship restricted the dissemination of Iribarren's work, which led to more common international adoption of a similar method which had been developed by Robert Y. Hudson at the USACE Waterways Experiment Station (WES) in Vicksburg, Mississippi, known as Hudson's equation. Iribarren's 1938 paper included the following formula, which calculated the weight of the armourstone or wave-dissipating concrete block required:

Iribarren continued to develop and refine this formula and his work on breakwater stability over the years, and in 1965 he published an improved version of the formula based on his ongoing research:

This improvement includes a friction coefficient, , and was a result of research and experiments by Iribarren and his colleagues during the period between the first (1938) and final (1965) publication of the Iribarren formula. Iribarren proposed that the force of a wave can be approximated by:

By then analysing the balance of forces for the rock or artificial element in question, the required minimum stone weight for stability could be determined both during wave run-up and wave run-down. Despite Iribarren's demonstration of its shortcomings, the Hudson formula continued to be used widely in its original 1959 iteration until the 1970s. A modified version of the Hudson formula is still commonly used for concrete breakwater elements, but for rock armour structures, it is valid only for situations with a permeable core and steep waves. It is also not possible to estimate the degree of damage on a breakwater during a storm with the Hudson formula. with whom Iribarren also collaborated on a two-volume engineering textbook entitled Maritime works: Waves and dikes which was first published in 1954, with a second edition in 1964.

Personal life Iribarren married Maria Hiriart, a French national, in 1939. His second brother, José Iribarren Cavanilles, was the municipal architect in Irún.

In February 1967, Iribarren died as the result of a fire whilst driving in a Fiat 1500 on the main Valencia-Madrid motorway, near Vallecas. An inscribed watch, gifted to him by a federation of fishermen in Gipuzkoa, was used to identify him.

Legacy and recognition Iribarren had a highly theoretical approach grounded in detailed observation and assisted by experiment, and his work continues to underpin several coastal engineering design methods. His findings have been further developed by modern research, including contemporary design methods such as the van der Meer formula, which expands Iribarren's methods to include allowance for irregular waves and the influence of storm duration. A bust of Iribarren is also displayed in the building in Madrid.