Belgian wetlands
Ground Investigation

The Sigma Plan

The Sigma Plan, designed by De Vlaamse

Waterweg NV, protects Flanders from flooding, at the same time boosting the valuable nature surrounding the River Scheldt.

In extreme weather conditions, the river and its tributaries can reach dangerously high water levels and even overflow their banks. The Sigma Plan involves creating sturdier and higher levees and a chain of natural flood control areas to catch excess river water. This gives the rivers room to flow and to overflow.

In addition to water safety, the plan also focuses on the development of the river’s nature, recreational facilities and local economies.

Vlassenbroek is one of the projects in this plan. It is a picturesque village popular for cycling and hiking. The Geotechnics Division, part of the Government of Flanders’ Department of Mobility and Public Works, provides expert advice in geotechnical engineering.

Project Summary

  • Name
  • The Sigma Plan
  • Location
  • Belgium
  • Date
  • December 2018 - 2020
  • Client
  • De Vlaamse Waterweg NV
  • Contractor
  • Aertssen Aannemingsbedrijf nv
  • Consultant
  • Geotechnics Division, Flemish Government


Piezometers were installed on several cross sections along the new levee. The levee is built on peaty ground and the aim is to monitor the dissipation of the pore water pressure and to steer and control the rate of elevation.

Bearing in mind the specific ground conditions, fully saturated and with a significant percentage of decaying peat, special care was taken during installation to ensure the results from the 15 piezometers would truly represent ground conditions.

The piezometers were connected to five five-channel wireless dataloggers which transmit data to a central Gateway, which in turn sends the data to Aertssen’s FTP.  This allows monitoring data in real-time so decisions can be taken in order to build a stable dike.

Geosense provided on-site technical services to assist with the method to drive in the piezometers as well as to train Aertssen on setting up the Wi-SOS wireless system.