The floods of 1953, 1993, 1995, 2021 and the almost flood in Rivierenland show that floods have major consequences. Before a flood people can evacuate preventively or vertical and during a flood people can flee, being rescued or permanently stay behind. This research focuses on fleeing and being rescued to a safe region. The research question is: ‘How much time does it take to flee to a safe region during a flood, and what are the core factors that determine the success of a rescue operation by a lifeboat in the Netherlands?’. To indicate how much time it takes for people to flee to a safe region, an experiment took place at test facility Flood Proof Holland in Delft. During this experiment 25 persons walked or bicycled over a parcourse divided into five rounds with different water depths, namely 0.2, 0.4 and 0.6 meter. Additionally, there were other variations, such as walking with a floating object, bringing luggage, bringing a domestic animal, fleeing during darkness and the addition of debris in the water. Time measurements took place during the experiment. If people cannot flee, rescue is needed. To gain more insight into rescuing of people during floods, a questionnaire is spread among experts. Relations between time measurements are found with the use of the Pearson moment correlation coefficient, paired t-test and determining the line by using intersept free linear regression. The relations are combined into a flow chart. Further, the time needed during a rescue attempt is combined into a formula. The navigation speed deviates for different water depths and types of lifeboats. Further, it is estimated by the experts that it takes 7½, 30 and 1 minutes from the contact with a person located at respectively a higher floor or attic, collapsed building and out of the water until having this person into a lifeboat. There is no direct singular answer to the research question, because it depends on the area where the flood takes place and the extent of the flood. Larger water depths increase the fleeing time. If a person decides to flee, it is recommended to walk with a bicycle or bring an air mattress. A stick is useful to check where the road is located. Avoid areas with a lot of debris and do not flee during darkness, except if this is inevitable to survive. People can also wait for rescue at a higher (dry) floor. For the rescue crew, number one priority is safety. Try to avoid to navigate through areas with a lot of debris as this may damage the lifeboat. Search the area systematically and make notes of where people are located.

Evacuation is a tool to minimise the loss of life and economic damages in flood (threat) scenarios. There is currently little data available on mass evacuation in the Netherlands to calibrate existing models or to develop new insights. This thesis aims to improve the methods used in the Netherlands to estimate the effectiveness of evacuation with methods developed by the United States Army Corps of Engineers (USACE). This USACE method includes a questionnaire that can be completed with authorities which in turn estimates the time it takes for authorities to give a warning to evacuate, how fast the warning spread through the population and how fast people will react to this warning. The results of this thesis showed that this “USACE assessment method” could be a valuable source of information to the Netherlands. However, due to the different threat scenarios and command structure(s) found in the USA several adaptations are needed to this USACE assessment method to make it usable in the Netherlands. However, this thesis also showed that the effect of (most) measures takes by authorities in the Netherlands will be limited by the heavy road congestion during evacuation. Traffic jams will quickly develop and any improvements with respect to evacuation will be cancelled out. So a recommendation that follows from this report is that authorities in the Netherlands shift their focus from an area specific evacuation strategy to a national evacuation strategy so new traffic management option can be developed that can limit these traffic jams. Another conclusion of this thesis is that agent based and micro level evacuation and loss of life models (models where people are modelled separately and area specific parameters are taken into account and thus include much more detail) add little to nothing to the evacuation strategies of the Netherlands compared to the current used macro models (models where an overarching view of the evacuation is used). Again, this is due to the large traffic congestion where traffic jams will almost immediately develop. When better traffic management options are available these micro level and agent based models may provide new insights on the evacuation effectiveness of specific areas.

Reinforcement measures are applied by water boards during critical conditions in an ultimate attempt to prevent flooding. However, the effect of these measures on the reduction in flood risk or failure probability of the flood defence is often unknown. This research focusses on the effectiveness of grass revetment reinforcement measures applied during critical conditions at the outer slope of river dikes. Reinforcement measures applied during critical conditions are characterised by time constraints and human errors. The effect of the reinforcement measure on the reliability of the flood defence is studied. A probabilistic model is developed to assess the failure probability of the reinforcement measure and the time needed to install the measure. A model named OPSCHEP-model is used to quantify the failure probability due to human action. The effect of the measures on the failure probability of the flood defence is calculated by a crude Monte Carlo simulation. It is found that the reinforcement measures are most effective for known weak spots in the flood defence. Weak spots that are to be found during emergency dike inspection result in a much lower reduction in the failure probability of the flood defence. The level of preparedness of the water board organization largely determines how effective the measures are in reducing the failure probability.