If you are looking for concrete information about sea tides on the Belgian coast and on the inland rivers, please contact the Ministry of the Flemish Community, Afdeling Kust – Vlaamse Hydrografie, Vrijhavenstraat 3, 8400 Oostende (059/554211) and/or Afdeling Maritieme Schelde, Tavernierkaai 3, 2000 Antwerpen (03/2220803). Some websites also provide information about this, e.g. http://www.vlaamsehydrografie.be or http://www.lin.vlaanderen.be/awz that gives all water levels.
At the Royal Observatory the earth tides are measured and studied using gravimeters. The small differences between the astronomical calculations (position sun, earth, moon) and the gravimetric measurements are investigated in detail to detect any other external influences. More information: https://www.astro.oma.be/en/scientific-research/seismology/.