Adaptation of marine locks against sea level rise

Abstract

There is a lot of uncertainty in climate change developments, and therefore in its consequences. For the flood defence system of the Netherlands, an important consequence of climate change is the sea level rise. Marine locks are large, rigid, and intricate structures, with a required lifespan of at least 100 years, for which often design decisions have to be made for many decades, which is not made easy by the uncertainty of sea level rise. In this thesis, it is first analysed by means of a probabilistic model how sea level rise alters the failure probability of a marine lock, and at what degree of sea level rise the safety norm is reached. This analysis also results in knowledge on the critical lock characteristics which are required to be improved once the safety norm is reached. Once the safety norm of a lock has been reached, the lock can either be adapted, or completely replaced. Adaptation concepts were developed to improve the critical lock characteristics. To compare these adaptations to the lock replacement, an adaptive pathways map was drafted, which visualises the implementation of adaptations and replacement in regard to the sea level rise development. It was found that the application of a minor adaptation is always preferable over a replacement, but that the benefits of a drastic adaptation depends on the functional and structural state of a lock. When a lock eventually has to be replaced, because of sea level rise or any other reason, the question still remains how to implement the uncertainty of sea level rise into the design. Instead of designing for a conservative sea level rise scenario, one can create an adaptive design. This is a structure which can be adapted over time, meaning costs are saved in case of a mild sea level rise scenario, but the lock can still be made sufficient in case of a severe scenario. Again, an adaptive pathways map was drafted to compare the application of a conservative lock to several adaptive lock alternatives. Unfortunately, no general recommendation can be made for adaptive lock designs, as the advantages and disadvantages of the alternatives depend on the specifics of a lock.