Flooding observations in Rotterdam

Abstract

This thesis focuses on identifying flood-prone locations, flood vulnerability and analyzing risk for the Municipality of Rotterdam. Municipal call center data of flooding complaints from 2012-2016 are investigated to identify the most flood-prone locations, which are called hot spots. This is performed by creating heat maps of the flooding record locations. The most dominant hot spots for multiple analyses are all situated in the sub districts of ‘Rotterdam Centrum’, ‘Delfshaven’ and ‘Noord’. Most flooding records are related to gully pots (≈55%), followed by sewer related problems (≈20%). Flood vulnerability is investigated by analyzing the influence of amount of inhabitants and degree of imperviousness on the hot spot locations. Both factors are involved in the origin of the hot spots. Investigating the influence of rainfall on flooding incidents pointed out an exponential relationship. From comparing differences in resulting flooding records for heavy/extreme rainfall events and cloudbursts, it can be concluded that Rotterdam’s drainage system is better capable at handling short heavy bursts of rainfall than consecutive hours of rainfall. The influence of seasonality on flooding incidents has also been investigated. There do appear to be seasonal patterns, which can be linked to blockages of gully pots by leave fall. In the risk & asset management analysis, asset maps related to infrastructure are created. They are used to calculate risk levels, based on the company values matrix of the Water Management department of Municipality of Rotterdam. The lower elevation of Rotterdam’s city center and surrounding downward slopes, which have been identified from the created elevation map, might contribute to the increased flood vulnerability and hot spots in the city center area.