Graduation of Chris Veldman

Adaptive design of the Wide Green Dike with multivariate uncertainty

• Professor of graduation: Dr. ir. Oswaldo Morales Napoles (TU Delft)

• Supervisors: Prof. dr. ir. M. R. A. van Gent (Deltares, TU Delft); Dr. ir. P. Mares Nasarre (TU Delft); Ir. T. Vrinds (Sweco Nederland)

The uncertainty paired with the effects of climate change impacts the design aspects of hydraulic structures. To comprehend the uncertainty of the evolving conditions, methods and models that differ from the traditional ones could provide a better understanding of the uncertainty and potential risks associated with a design.

Hydraulic structures are designed to withstand loading conditions related to extreme environmental scenarios. Such natural hazards are characterized by the shared dependence of several random variables. Multivariate probabilistic design clears the way for exploring dependencies between design variables. A multivariate approach models the joint occurrence of a combined condition, revealing new insights e.g., the correlation between wave height, wind speed and water level. Next to incorporating new models that estimate the uncertainty and changing conditions related to climate change, there could be a leap forward could in design methodology. Adaptive design strategies can provide a way to mitigate over-designing hydraulic structures. To cope with the uncertainty of sea level rise, this methodology aims at handling the uncertainty in long-term decisions by emphasizing adaptivity in a design.

This thesis aims to develop a multivariate probabilistic tool to provide insight into incorporating adaptive design strategies, and to gain extra information that contributes to assessing the feasibility of the Wide Green Dike concept given the uncertainty of sea level rise.

A multivariate model using a vine copula is created to approximate the joint behaviour of the extreme hydraulic boundary conditions of the Wide Green Dike project. The results showed that by accounting for the joint behaviour of the extremes and the uncertainty and variability of design conditions, significant reductions in the design could be realised compared to designing in a deterministic manner. The deterministic design increased the cross-sectional area of the dike by 150% compared to the multivariate probabilistic design with a sight year of 2150.

To explore the adaptive design strategies, several strategies are created using the multivariate probabilistic design approach. The strategies consist of an initial design with a certain sight year and one or multiple adaptions during its lifetime up to 2150. The strategies are assessed based on the business case, up-scaling of the clay refinery in the Ems-Dollard estuary, the impact on the Natura 2000 area and feasibility. It was found that incorporating an adaptive strategy could promote the business case and help mitigate the risk of over-designing.