Coastal cities and communities are threatened by Sea Level Rise (SLR). Designing adaptations to protect against the rising sea requires a novel approach. With changing conditions, a broader approach considering multiple climate scenarios is required. A city facing an increasing threat from sea levels is Venice, one of the UNESCO world heritage sites. To protect the historic Italian city against floods, the MOSE barrier was constructed by the Italian government.
In 2020, the MOSE barrier was used for the first time. The mobile barrier closes when high water levels are foreseen in the city, preventing floods. Due to SLR, it is anticipated that the barrier will have to close more in the future, leading to questions about the functionality of the barrier when water levels rise. This might require adaptations or alternatives for the MOSE barrier.

The main objective of this thesis is to explore the potential of the framework proposed by Rosner et al. (2014) to evaluate the economic feasibility of an adaptation strategy against sea level rise in the city of Venice.
This framework assesses the potential regrets (monetary losses) on the decision to invest in an adaptation strategy accounting for errors in the evaluation of the level of sea level in the future. The framework incorporates trends based on historical sea level observations, including the uncertainties around these trends.

First, different methods of calculating design values under varying conditions are compared. This comparison is focused on different non-stationary Extreme Value Analysis (EVA) distributions. Due to SLR, a stationary and thus constant situation is not valid for Venice. This leads to the choice of the Rosner framework since it evaluates the feasibility of adaptations under varying conditions.

The regret of adapting or not adapting to a trend or SLR scenario is calculated from the damages associated with that scenario and the costs of the adaptation. The damages are computed by calculating the number of MOSE barrier closures for the different scenarios and multiplying this number by the costs that are related to a closure event. The adaptation that was chosen for evaluation is raising the entire city by 30 cm. This is accomplished by injecting seawater into a deep soil layer underneath the city.

The analyses resulted in smaller expected regrets when the choice is made to adapt. This was the case for all SLR scenarios, the difference between the adapt and not adapt regrets is larger for higher levels of SLR. This includes a higher SLR scenario due to a trend with large uncertainty. This is under the assumption that the adaptation, lifting the city, will work, the technical feasibility of this method was not investigated in this thesis.
A more precise calculation of the number of closures is advised. However, it is evident that adaptations are required to keep the MOSE barrier functional and the city of Venice safe from high waters. Raising the city will allow more time to evaluate which alternative to the MOSE barrier is best suited for the future.