Experimental research on the factors which influence the fleeing time and rescue time of people evacuating flooded areas

Abstract

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.