Pieter Jacobus Wemelsfelder Explained

Pieter Jacobus Wemelsfelder
Birth Date:18 November 1900
Birth Place:Goes, The Netherlands
Death Place:Almen, The Netherlands
Citizenship:Netherlands
Nationality:Dutch
Fields:Civil Engineering
Hydraulic Engineering
Hydrometry
Workplaces:Rijkswaterstaat
Waterloopkundig Laboratorium
Alma Mater:Delft University of Technology
Known For:Probabilistic approach to determining flood levels for storm surges
Honorific Prefix:ir.

Pieter Jacobus (P.J.) Wemelsfelder (18 November 1907 – 1 July 1995) was a Dutch hydraulic engineer who made significant contributions to the field of hydrometry in the Netherlands, and in hydraulic engineering internationally. In addition to his involvement in the design and planning of the Delta Works, he published widely and is notable for the first use of probability theory in the design of flood levels.

Wemelsfelder introduced a systematic approach to understanding and predicting the occurrence of storm floods, considering both the characteristics of the sea's probable and possible heights and the human and economic interests at stake. His methodology involved creating frequency curves for storm floods, using a standard frequency curve applicable to different gauges worldwide, and classifying storm floods based on their probability of exceedance. This classification system helped in understanding the variability of maximum storm floods over different time periods.

Wemelsfelder emphasised the importance of considering both the period and risk when determining design levels, advocating for a two-dimensional approach to flood protection. His approach required establishing a frequency curve for each gauge, determining the period during which the risk is present, and choosing an acceptable total risk value for serious damage, generally not exceeding 10%, and as low as 0.1% for critical areas. He noted the need to balance the costs of safety measures with the economic and human values they protect, and recognised the importance of incorporating contingency in design to account for uncertainties.

The body set up by the Dutch Government in response to the 1953 North Sea Flood, the Delta Commission, adopted Wemelsfelder's probabilistic methods, setting design levels based on a risk of total loss of 1 in 1,000 years for critical areas, ensuring a high level of safety. His contributions have had a lasting impact on coastal engineering and continue to inform the design and implementation of flood defences in the Netherlands and beyond.

Life

Wemelsfelder was born in Goes, the son of Jacob Abraham Wemelsfelder and Jannigje Verschoor, in 1907.[1] After completing his studies at the Delft University of Technology, Wemelsfelder worked at the Waterloopkundig Laboratorium and later at Rijkswaterstaat, where he served as the head of the Hydrometric Department of the Water Management and Movement Directorate. One of his major accomplishments was the development of methods and instruments for hydrometry in the Netherlands.[2] [3]

Wemelsfelder introduced a probabilistic approach to determining design flood levels for storm surges in the Netherlands. Prior to his work, flood protection measures were based on a deterministic approach that relied on the highest previously recorded water levels, along with some estimation. For example, the height of the Afsluitdijk was determined based on the highest observed storm surge,[4] with the height of the crest determined based on insufficient data about wave run-up. This became apparent soon after the first significant storm surge following the completion of the dike in December 1936, when water in the Wadden Sea reached to around half a metre below the dike.[5]

n(h)/n

, where

n(h)

represents the number of times the level

h

was exceeded during

n

years, closely followed a straight line when plotted on logarithmic paper.[6]

Prior to Wemelsfelder's work, S.H.A. Begemann had applied statistical methods to hydrological aspects such as precipitation and runoff for irrigation. In the United States, publications on stochastic hydrology such as those by Allen Hazen and others had been appearing since the early twentieth century.[7] However, Wemelsfelder's statistical analysis of water levels measured between 1888 and 1937 at Hoek van Holland enabled the derivation of a probability distribution of storm surges. He published his findings in the Dutch journal Dutch; Flemish: de Ingenieur in March 1939, which revolutionised the way flood protection measures were designed in the country.[8] [9]

By using a frequency curve on a logarithmic scale, Wemelsfelder showed that an effective statistical overview of storm surges could be obtained. His 1939 paper demonstrated that the structure of the distribution of storm surges over the years, both in terms of strength and frequency, can be accurately represented by a probability law.

In 1939, the establishment of the Dutch; Flemish: Stormvloedcommissie (Storm Surge Commission) was prompted by concerns regarding the state of many dikes in Zeeland. Under the leadership of Johan van Veen, the commission adopted Wemelsfelder's probabilistic approach as the basis for determining the probability of water level exceedance and the calculation of dike heights. This was a departure from the earlier approach of relying solely on previously recorded high water levels.[10]

Despite the commission's recommendation to raise the levels of the dikes, the Government of The Netherlands did not take action, and the dike system remained vulnerable throughout World War II. After the war, attention turned to rebuilding efforts, and this was exacerbated in 1953 further to a catastrophic flood that claimed 1,836 lives in The Netherlands, and caused billions of guilders in infrastructural damage.

The storm surge associated with the 1953 flood saw water levels reach 3.85 metres above Normaal Amsterdams Peil (NAP) at Hoek van Holland, higher than the crest height of the dikes which had been determined based on previously recorded highest water levels (3.28 metres above NAP) at the same location.[11] [12] [13] [14]

In response, the Dutch Government formed the Dutch; Flemish: Deltacommissie (Delta Commission), which was charged with making recommendations for reducing the risk of such disasters. The commission relied heavily on the analysis and solutions put forth by the Storm Surge Commission, which had already adopted Wemelsfelder's probabilistic approach for determining dike heights.[15] [16]

The Delta Commission recommended a target exceedance frequency of 10−4 per year as the basis for design levels in central Holland, and its work led to the enactment of the 1958 Delta Act. Wemelsfelder's work actually considered a factor of safety that increased the exceedance frequency to that which corresponds to m=10−5, where m is the acceptable risk. This corresponds to a total loss figure of 1% in a 1000-year period.[17]

Wemelsfelder made significant contributions to the Delta Commission's analysis and recommendations, and was active in research throughout his career, publishing a number of technical papers in Dutch and English.[18] [19] [20] [21] [22] [23] His findings continue to inform flood protection measures in the Netherlands today.[24] [25] [26] [27]

Activities outside hydraulic engineering

In 1946, Wemelsfelder published a 358-page monograph focused on topics such as cultural development, societal change, the structure of an organic society, governance, legislation, and international order, entitled Dutch; Flemish: Plan voor een redelijke Nederlandse samenleving (English: Plan for a reasonable Dutch society).[28]

The book set out Wemelsfelder's thoughts on how The Netherlands could organise society in political and economic fields in the immediate aftermath of the Second World War and dealt with issues including combating unemployment, the establishment of a savings credit bank, reorganisation of banking and industry, pensions, the introduction of child allowance and the introduction of a separate income for married women.[29]

Selected Publications

Between 1965 and 1972, Wemelsfelder prepared reports on various storm surges which occurred in the Netherlands. All reports from this period are available at TU Delft Repository: Link:

See also

Notes and References

  1. Web site: Genealogie . Coret . Birth Pieter Jacobus Wemelsfelder on November 18, 1907 in Goes (Netherlands) . 2024-07-27 . Open Archives . en.
  2. d' Angremond . K. . 2001 . Pompen of verzuipen . Sink or swim . nl . De Academische Boekengids . Oct . 29 . 7–8 . 3 April 2023.
  3. Web site: Pieter Jacobus Wemelsfelder . 2023-12-28 . Flevolands geheugen . nl.
  4. Stuvel . H. J. . 1957 . Het eerste offensief: 25 jaar afsluitdijk 1932-1957 . The first offensive: 25 years of the Afsluitdijk, 1932-1957 . Staatsdrukkerij en Uitgeverijbedrijf . 3 April 2023 . nl.
  5. Book: Thijsse, J. Th. . Een half eeuw Zuiderzeewerken 1920-1970 . H.D. Tjeenk Willink B.V., Groningen . 1972 . 156–160 . 5439270 . nl . A half century of the Zuiderzee Works 1920-1970 . 3 April 2023.
  6. Wemelsfelder . P. J. . 1938 . Beknopte Nota over de Frequenties van Stormvloeden . Concise note on the frequencies of storm surges . Rijkswaterstaat . nl . 3 April 2023.
  7. Vreugdenhil . C. B. . Alberts . G. . van Gelder . P. . 2001 . Waterloopkunde: een eeuw wiskunde en werkelijkheid . Hydraulics: A century of mathematics and reality . Nieuw Archief voor Wiskunde . Dutch . S 5, dl 2 . 3 . 266–276 . 0028-9825 . 3 April 2023.
  8. Wemelsfelder . P. J. . 1939 . Wetmatigheden in het optreden van stormvloeden . Patterns in the occurrence of storm surges . De Ingenieur . nl . 54 . 9 . 3 April 2023.
  9. van Dantzig . D. . David van Dantzig . 1954 . Mathematical problems raised by the flood disaster 1953 . Proceedings of the International Congress of Mathematicians, Amsterdam Sept. 2 - 9 . . 218–239 . 15 December 2023 . Wageningen University.
  10. Maris . A. G. . De Blocq van Kuffeler . V. J. P. . Harmsen . W. J. H. . Jansen . P. P. . Nijhoff . G. P. . Thijsse . J. T. . Verloren van Themaat . R. . De vries . J. W. . Van der Wal . L. T. . 1961 . Rapport Deltacommissie. Deel 1. Eindverslag en interimadviezen . Delta Committee Report. Part 1. Final Report and Interim Recommendations . Rapport Deltacommissie . nl . 3 April 2023.
  11. d'Angremond . K . Kooman . D . 1986 . Eastern Scheldt storm surge barrier . International Journal of Project Management . 4 . 3 . 149–157 . 10.1016/0263-7863(86)90046-3 . 0263-7863 . 3 April 2023. subscription .
  12. Web site: Watersnood, een reconstructie van de watersnoodramp in 1953 . Flood Disaster, a Reconstruction of the 1953 Flood Disaster . 2023-04-02 . nl . lab.nos.nl.
  13. Web site: The Watersnoodramp: the Dutch battle against water . 2023-04-02 . www.europeana.eu . 31 January 2019 . en-GB.
  14. Wemelsfelder . P. J. . 1953-01-01 . The disaster in The Netherlands caused by the storm flood of February 1, 1953 . Coastal Engineering Proceedings . 1 . en . 4 . 18 . 10.9753/icce.v4.18 . 2156-1028 . 3 April 2023. free .
  15. Web site: Embrechts . P. . January 31, 1953 and 9/11: living with risk. Presentation by Professor Paul Embrechts, London School of Economics and Political Science . 2023-04-02 . London School of Economics and Political Science . en-GB.
  16. Kruizinga . Samuël . Lewis . Pepijn . 2018-12-13 . How High is High Enough? Dutch Flood Defences and the Politics of Security . BMGN - Low Countries Historical Review . 133 . 4 . 4 . 10.18352/bmgn-lchr.10365 . 158747369 . 2211-2898 . 3 April 2023. free .
  17. Wemelsfelder . P. . 1960 . On the use of frequency curves of stormfloods . Coastal Engineering Proceedings . 7. 33. 617–632 . 3 April 2023.
  18. Wemelsfelder . P. J. . 1971 . De stormvloed van 21 en 22 november 1971 . The storm surge of 21st and 22nd November 1971 . Rijkswaterstaat . nl . 3 April 2023.
  19. Wemelsfelder . P. J. . 1965 . Bodemdaling, blijvend actueel aspekt van de Nederlandse waterbouw . Land Subsidence, a Permanently Relevant Aspect of Dutch Hydraulic Engineering . Overdruk van Bericht No. 10 van de Nederlandse Vereniging voor Landaanwinning (Reprint of Report No. 10 from the Dutch Association for Land Reclamation) . en . 3 April 2023.
  20. Wemelsfelder . P. J. . 1948 . Verslag metingen Voedingsduiker Maastricht: 2de serie . Report on Measurements of Maastricht's Feeder Culvert: 2nd Series . Rijkswaterstaat . nl . 3 April 2023.
  21. Wemelsfelder . P.J. . 1957 . Origin and effects of long period waves in ports . Permanent International Association of Navigation Congresses (PIANC), XIXth International Navigation Congress . SII . C1 . 1–10 . 3 April 2023.
  22. Book: Conference on The North Sea Floods of 31 January - 1 February 1953 . 1954 . . 978-0-7277-4509-5 . London . en . 10.1680/cotnsfo1953.45095 . Institution of Civil Engineers.
  23. Book: Jelgersma . S. . Zeespiegelbeweging en bodemdaling: voordrachten gehouden voor de algemene vergadering van de Nederlandse Vereniging voor Landaanwinning, gehouden op 1 mei 1963 . Smits . H. . Wemelsfelder . P.J. . 1965 . Ceres . nl . Sea Level Movement and Land Subsidence: lectures given at the general meeting of the Dutch Association for Land Reclamation, held on May 1, 1963.
  24. Wemelsfelder . P. J. . 1972 . De stormvloed van 13 november 1972 . The storm surge of 13th November 1972 . Rijkswaterstaat . nl . 3 April 2023.
  25. Expertisenetwerk Waterveiligheid . 2016 . Fundamentals of flood protection . Expertisenetwerk Waterveiligheid . 2 April 2023 .
  26. Web site: P.J. Wemelsfelder reports and papers stored by TU Delft Repositories . 2023-04-02 . repository.tudelft.nl.
  27. Web site: Onderzoeksrapporten - P.J. Wemelsfelder. Research Reports - P.J. Wemelsfelder . 2023-04-02 . Rijkswaterstaat Publicatie Platform . nl.
  28. Book: Wemelsfelder, P. J. . Plan voor een redelijke nederlandse samenleving . 1946 . L. J. C. Boucher . nl . Plan for a reasonable Dutch society . 10270645 . PJ Wemelsfelder . 28 December 2023.
  29. Book: Wemelsfelder, P.J. . Plan voor een redelijke Nederlandse samenleving . L.J.C. Boucher . 1946 . The Hague . nl . Plan for a reasonable Dutch society . 3 April 2023.

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