The Ramspol Barrier, an inflatable storm surge barrier, is an integral component of the flood protection system for the Zwarte Meer and its hinterland. However, its current operational procedure faces several challenges that compromise flood safety, cause disruptions for the shipping industry, and significantly burden the operation team. The current operational procedure activates specific steps based on predefined water level thresholds, often mobilizing the operation team and disrupting shipping without ultimately leading to a barrier closure. It is also questioned whether closures are always the best strategy for optimizing flood safety in the system.

This thesis aims to improve the operational procedure of the Ramspol Barrier by balancing flood safety, operational burden, and disruptions to vessel navigation.

A comprehensive system and data analysis were conducted to understand the dynamics of high-water events, which are primarily driven by onshore winds, precipitation, and wind-induced water setups. These conditions, coupled with restricted drainage at the Afsluitdijk and increased discharges from the ZwarteWater and IJssel, result in rapid water level rises at the barrier. The current operation protocol triggers closure at +0.50 m NAP and an inland flow, protecting the Vecht Delta. However, this blocks outflow, delays vessel movements, and causes water accumulation in the Zwarte Meer. The analysis further revealed a strong correlation between higher water levels and wind setup. In comparison, the impact of discharges from the IJssel and ZwarteWater on higher water levels was minimal. The findings also highlighted the growing strain on the operation team and the disruptions faced by the shipping industry over recent years.

Nine scenarios were simulated using a developed reservoir model to assess the system’s sensitivity to wind setups and discharges, the effect of adjustments to the operation procedure, and the model’s predictive capabilities. The simulations revealed that closures during receding or stagnating water levels, or when wind setup was already developed, sometimes resulted in higher water levels than non-closure scenarios. In cases where water levels were between +0.40 m NAP and +0.50 m NAP, navigation could often be maintained, provided wind setups were reducing or stagnating, and no significant discharge peaks were predicted. Moreover, minor wind events at initial water levels above +0.50m NAP frequently triggered unnecessary closures, which could elevate water levels, highlighting the need for more robust closure criteria based on sustained flow rather than momentary fluctuations. When multiple peaks
occurred, the timing and proximity of these peaks played a crucial role in determining the impact on water levels. Earlier closures reduced water levels but extended operational disruptions, while higher discharges led to faster water level rises post-closure, requiring earlier openings. Lastly, enhancing the ability to predict critical water levels and closure and opening criteria can significantly benefit both operational teams and the shipping industry. Implementing 24- to 48-hour forecasts would enhance planning by ensuring teams are on-site when needed, minimizing unnecessary disruptions, predicting the timing and likelihood of Ramspol Barrier closures, and enabling the shipping industry to adjust schedules to reduce waiting times.

The results indicate that an adaptive, forecast-driven approach to barrier operation could potentially improve flood protection, reduce disruptions for the shipping industry, and alleviate the team’s operational burden.

Van Sickle Island, located in the Suisun Marsh in the San Francisco Bay Area, has experienced multiple levee breaches in the past. Due to the large social and economic implications of flooding, questions have arisen about whether the current management of the island is still feasible. This project, therefore, aimed to find the most financially favorable management plan for the upcoming 50 years. First, an understanding of the system was obtained through a site investigation, a multivariate analysis, and a hydrodynamic model. It was concluded that discharge, tide, air pressure, and wind setup all contribute to the water level. These variables were then used as input for a 1-dimensional hydrodynamical model, which quantifies their effect on the water level. Subsequently, four management plans were considered: status quo, raising the levees, conversion into an estuarine wetland, and abandoning the island. To allow for comparison between these management plans, a cost-benefit analysis and a net present value calculation were performed for every plan. One of the major contributors to the costs is risk. Risk is defined as the product of the probability of failure and the consequence of that failure. The failure mechanism assessed is overflow, as this is the most relevant one. To quantify this failure probability, a statistical model was developed. This model includes an extreme value analysis and an event tree. Due to large uncertainties in the behavior of both the levee and the water level over time, the original 50-year lifetime of the management plan was deemed too ambitious. Therefore the lifetime was reduced to 10 years. The conclusion of the cost-benefit analysis and the net present value was to convert Van Sickle Island into an estuarine wetland. This is because it was the only management plan that was profitable after 10 years. The net present value was found to be equal to $14,924,048.