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.

Wemelsfelder emphasised the importance of considering both the period and risk when determining design levels, advocating for a two-dimensional approach to flood protection.

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.

[1][2] 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.

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.

[5] In 1938, Wemelsfelder introduced a significant change in the design approach through a brief note on the frequency of storm surges, in which he carried out a statistical analysis of water levels measured between 1888 and 1937 at Hoek van Holland to derive the probability distribution of such events.

[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.

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.

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.

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.

[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.