During a failure event on the 2nd of November 2023, non-closure of the spill gates in IJmuiden resulted in sea water inflow into the adjacent water system. This water system consists of the North Sea Canal, Amsterdam-Rhine Canal and multiple side rivers and basins. Considerable research is available on the ability of the complex IJmuiden in discharging the fresh water system and the connected polders. However, research on sea water flowing into the water system is limited. This research focusses on the behavior of a flood wave due to sea water retaining failure of the spill-lock complex in IJmuiden. Several scenarios are modeled in which sea water level, the failure mechanism and the duration of failure are varied. The model is created with the software of HEC-RAS. With the probabilistic analysis in combination with an estimation for the costs of damage, the research concludes with a flood risk estimation for 6 hours of spill failure.

Hospitals are part of the vital and vulnerable infrastructure in the Netherlands. Failure of such infrastructure may have severe consequences on a national scale. The Dutch flood risk management approach aims to prepare hospitals for floods through spatial adaptation. However, the current policy does not prescribe concrete guidelines for consistent decision-making and implementation of flood strategies to increase flood preparedness of hospitals. The engagement of stakeholders in this process is also arbitrary.

The main research question is: “How can flood preparedness of hospitals in the Netherlands be assessed and improved?” The main aim of this research is to quantitatively assess the flood preparedness of hospitals to enable comparison between flood strategies and to make recommendations on which stakeholders should be engaged for the implementation of flood strategies and how this can be achieved.

Six different flood preparedness indicators were selected that together describe flood preparedness of hospitals. Based on these indicators, the impact of several flood scenarios on the Reinier de Graaf Gasthuis (RdGG) and Erasmus Medical Centre (EMC) was quantitatively assessed. The costs per flood strategy are highest for “shelter in place with additional measures”, followed by both “shelter in place without additional measures” and “preventive evacuation”. “Accept” is least expensive. The number of fatalities per flood strategy for the RdGG (0,2 to 2,1 fatalities) is much lower than for the EMC (18,8 to 195,3 fatalities). Furthermore, it was determined which stakeholders should be engaged for the implementation of each flood strategy. Experts who have experience with hospital floods were interviewed to obtain their view on how these stakeholders could be engaged.

In conclusion, essential hospital functions can be categorised based on the flood preparedness indicators and flood strategies can be quantitatively compared. For the RdGG and EMC, "shelter in place with additional measures" yield the least amount of fatalities and is therefore the "best" flood strategy. The Executive Board of a hospital, hospital personnel, water boards, municipalities and safety regions should be engaged to realise the implementation of flood strategies. Experts with lived experience recommended to engage stakeholders through legislation or creating awareness.

It is recommended to calibrate the number of fatalities based on historical flood events and to analyse the vulnerability of the regional healthcare system to supplier failure during floods.