Apparently here is some water element in the landscape. It's called 'Bomputteke' after a German V2 bom hit this place during WW2.
You can read about it in Dutch on Facebook (https://www.facebook.com/groups/806596192836980/permalink/1892631750900080/).
Also on Geopunt Vlaanderen (https://www.geopunt.be/kaart?viewer_url=https%3A%2F%2Fmaps.geopunt.be%2Fresources%2Fapps%2FGeopunt-kaart_app%2Findex.html%3Fid%3D8ab2284f77cfe8ab0177e93c383d00ac) the element is visible.