Jos Wessels MSc
- asset management
The Netherlands is known throughout the world for its expertise in the field of water safety. TNO has always played a major role in this, both in terms of the philosophy of the risk approach and the development of the related methodologies. On the basis of this extensive knowledge and experience, TNO specialists work with other organisations on the further development of a risk approach to keep everyone's feet stay dry.
Since the 1953 flood disaster, the risk approach has developed rapidly. Initially it focused on exceedance probability for high water levels, but this is now emphatically shifting towards flood risk. The next interim step in the approach will be flooding probability. TNO has contributed to this development with specialist knowledge of probability calculations and 'probabilistic design'. Calculating the flood risk for a length of dike, a dam or a lock is a difficult undertaking. Combining these probabilities into flooding probabilities for dike rings demands the utmost in terms of computing time as well as defining the models. That is why derived models have been created. These are simpler to use, but give sufficient certainty that water safety requirements are met. TNO are the people to contact for issues in this area.
Deltares and TNO work together to fully utilise their knowledge to ensure water safety. Deltares focuses on water, soil and the subsurface, TNO on structures. We are also collaborating with Deltares in the development of risk-analysis methodology and asset management. For example, TNO is involved in creating the statutory assessment instruments (WTI, Wettelijk Toets Instrumentarium) that are being developed by Deltares and Rijkswaterstaat. A joint knowledge-investment project has also been launched to focus on achieving greater understanding of ground/structure interaction and on improving construction methods. This is resulting in improved methodologies.
TNO contributes to the development of models and guidelines for calculations relating to hydraulic structures in flood defences such as locks, dams, embankments and weir. These often complex structures can have a significant effect on flood probability in a dike ring. Specialist knowledge of structures and materials makes it possible to assess more accurately whether a structure complies with safety requirements. Particularly in doubtful cases, if a structure does not comply with the usual derived guidelines, more detailed and complex calculation models - and, if necessary, measurements - can ensure that structures comply with generally accepted safety standards, or that the necessary modifications can be made at minimum cost. This helps to extend the useful life of hydraulic structures. Our work in this field always takes account of societal challenges such as lack of space; for example, we were involved in a study of the possibilities for multifunctional flood defences.