Delta Life 12

27 DELTARES, OCTOBER 2019 Robust quay walls for Amsterdam The maintenance work is overdue onmany quay walls in Amsterdam. One quay has even collapsed; some others are subsiding, with all the inevitable consequences for people and traffic. Deltares is helping the city of Amsterdam to speed up the replacement of quay walls using a smart approach, and identifying the locations that are most at risk. T he centuries-old canals, charac- teristic buildings, bridges and quays of Amsterdam attract many thousands of tourists every year. As well as being a wonderful spectacle, the 850 bridges and 200 kilometres of quay walls on wooden piles are also important traffic infrastructure. And that is where things have sometimes gone wrong in recent years: mainte- nance is overdue onmany of these bridges and quay walls, and they are coming to the end of their lifespan. Inaccurate The replacement of a quay wall is not an easy operation and there is a risk for surrounding buildings. In the past, the city of Amsterdamhas used survey instruments – levels – tomeasure sub- sidence in buildings. That process took at least two years: it was often impos- sible to draw on historical data and the measurements were not very accurate. Deltares is now helping Amsterdam to catch up with the rest of the world by quickly identifying which quay walls are most likely to subside. We are working with the city on the formulation of a knowledge agenda and the development of an assessment framework and the associated protocol. That involves close collaboration with TNO, DelftUniversity of Technology and the Amsterdam Institute for Advanced Metropolitan Solutions (AMS). That will make it easier for the city to identify the quay walls that have to be replaced first. Satellitemeasurements Deltares and DelftUniversity of Techno­ logy developed away of mapping out subsidencemuchmore quickly. Deltares transformed Delft's scientific knowledge into a practical method for the client that uses satellitemeasurements. These measurements are already available for the last ten years and newdata are added every eleven days. 'This software can identify subsidence immediately and repair work on the quaywalls can start two years earlier,' saysMandy Korff, a consultant with Deltares. Themethod shows whether there is a probability that is higher or lower than five percent that a building is subsiding more than twomillimetres per year. This is a threshold based on practical experience that indicates how stable the buildings are. The procedure has been validated in three case studies and it was found to be reliable. In addition, Deltares is also developing the associated user-friendly software for the procedure. This software can probably also be applied to other projects in the future. For more information: mandy.korff@deltares.nl BY BONNE VAN DER VEEN