Heavy rainfall can lead to flooding in cities. In order to prevent damage, it is necessary to know how much rain falls and where. Dr Marie-Claire ten Veldhuis is investigating reliable ways of collecting this type of data.
Cities in the Netherlands can be characterised by more and more paved surfaces, fewer green spaces and less open water. Anyone can see what happens during a cloudburst: the sewers are unable to cope with the enormous amount of water, drains overflow and streets and cellars become flooded. The warming of the North Sea is expected to increase the frequency of flash flooding in the Netherlands.
It is time to find solutions that are capable of coping with such peak loads. First, however, we need to identify the places where these solutions are needed. In other words, we need to know where the rain actually reaches the ground, and in what quantities. ‘We currently do not have enough information about that’, explains Assistant Professor of Urban Water Systems Marie-Claire ten Veldhuis, of the Department of Water Management (Civil Engineering and Geosciences). Weather stations, rain radar and a mobile app are expected to change this situation. Ten Veldhuis is currently testing 20 weather stations on the campus in Delft. These types of stations are never installed in cities, because they would be too close to the built area, according to the rules set by the World Meteorological Organisation. ‘But for urban water management, they do need to be built in the city. We are investigating how many weather stations are needed in order to generate a representative image’. Several primary schools in Delft are participating in the project as well.
After the testing phase, weather stations will also be installed in Rotterdam and Amsterdam. Ten Veldhuis plans to combine the data generated by the stations in Rotterdam with those from the advanced rain radar, which the City of Rotterdam installed on the Nationale Nederlanden building this year, in collaboration with the department of radar expert Herman Russchenberg. This system is capable of measuring rainfall by street, at a height of 150 metres above the ground. It is not able to establish with any certainty where the most raindrops hit the ground. The influence of the wind is difficult to predict, as the wind is affected by buildings. For this reason, Ten Veldhuis wants to use people as rain gauges in Amsterdam – a system she refers to as citizen sensing.
Participants receive an app with which they can report how much rain is falling (or has fallen) in their streets. Ten Veldhuis developed this app in collaboration with the intelligent systems group (Electrical Engineering, Mathematics and Computer Sciences). Her Bachelor’s students will be testing it. ‘In this way, we hope to combine a large amount of information, which can then be used for modelling’. The ultimate goal is to develop something that will be of benefit to everyone: weather radar at street level.