Antiquarian observations carried out on the course on the river Deûle in Lille often mention Gallo-Roman material associated with river deposits. Recently acquired archaeological data confirm this incidence of forms, at least from the rue du Port down to the rue de Paris. The antique occupation of the banks is illustrated by the discovery of a small building of unknown designation (rue des Tanneurs). In the IInd century AD there occurs in the minor bed a major erosion event, followed in the IIIrd century by the rapid deposition of silt and peat. The causes of these probably local hydrographical changes are hard to make out. The fine sedimentation favoured a detailed palynological recording (rue de la Riviérette) and from this the agro-pastoral transformations that developed between the time of the Late Empire and that of the construction of the mediaeval walls can be identified and discussed. A modest settlement in the minor bed dates back to the viith century at the Tanneurs. On the same site, the Becquerel bears witness to the first real canal work (xith century). Not subjected to the topography of the site, the canal constitutes the ex nihilo creation of a hydrographical axis. While mediaeval urbanization developed, the older course long remained subject to flooding, with deposits of clays silts, and the vicinity was not built upon. The successive systems of fortifications naturally tended to use it as a ditch defence (rue Patou, rue de la Riviérette), while, intra muros, these low and wet plots of land, which are crossed with urban canals, remains long dedicated to crafts (Tanneurs).