Measuring sagging sewers from space

Published: 14 July 2014

It will soon be possible to monitor sagging sewers from space. This is an improvement on the traditional measurement methods, which are imprecise and extremely expensive. This idea came from Hansje Brinker, Waternet and Deltares, and it recently won an innovation award from Business Competition in Water. It will be elaborated further in the months to come. The jury described it as "a highly promising technology in the hands of an excellent team”. The prize: an innovation award of €25,000. In the collaboration with Hansje Brinker and Waternet, Deltares contributes knowledge about the behaviour of the subsurface. Deltares can use satellite measurements to describe the effect of surface settlement on sewers.

Traditional measurement methods imprecise and expensive

Many large cities are built in river estuaries on soft soil. That is the case for Amsterdam, Rotterdam and many cities in other countries. Sagging sewers can be the result, interfering with the flow of the sewage and blocking the sewers. When there is severe rainfall, the sewers will not be able to drain away the water adequately, and streets get flooded. Waternet is the agency responsible for managing sewers in the Amsterdam area, and it is very much aware of the problem of sagging sewers. Jojanneke Dirksen, a sewer specialist with Waternet: “The traditional measurement methods for mapping settlement are imprecise and very expensive. Satellite measurements could be a major advance and so we are very interested in this new technology.”

Satellite images provide millimetre precision

Jos Maccabiani, a director with Hansje Brinker: “From a satellite, the settlement of streets and buildings can be measured with millimetre precision. The challenge for us is that our measurements look at the street, and not the sewer, which can be several metres further down. This innovation award will allow us to call in Deltares. As a research institute for water and the subsurface, they can help us to translate our measurements to monitor the sagging of the sewers. Waternet is also supplying its expertise and data and so we think we will be able to use this satellite technology for sewer management within the short term.”

 

Visualisation of deforrmation measurement: green spots are stable, red spots are subsiced. The diagram shows the deforrmation of one of the red spots in years.

Visualisation of deforrmation measurement: green spots are stable, red spots are subsiced. The diagram shows the deforrmation of one of the red spots in years.