The “Séré de Rivières” type fort: geomorphological approaches to polemolandscapes (GIS, LiDAR, military archives). Example of the fortified belt of Reims (France)

The purpose of this research is to study the place of the “Séré de Rivières” type fortification in the geomorphological dimension of the war landscape. A multiscalar approach is proposed to analyze the geomorphological context of this defensive system. It appears that the rationalization of the relief is effective at all scales: the defensive system is rooted in the eastern mountain massifs and in the cuesta system of the Paris Basin; the strongholds of Reims locks a funnel of consequent valley (Vesle river) by basing itself on the reliefs associated to the cuesta of Île-de-France (reverse side of the cuesta, residual hills, outliers). The cross-analysis under GIS of an airborne LIDAR survey of the Nogent-l'Abbesse fort sector (fortified belt of Reims), and of documentary and field sources, provides a diachronic vision allowing to sort out the forms and to polyphase the “morphogenesis” of this polemolandscape. Its construction and modernization (1875-1892) testify to an architectural standardization, a remarkable adaptation to the reliefs and the reasoned use of local geomaterials. Its integration into the defense networks of the WW1 induced mutual pedological (pedoturbation), morphological (bombturbation) and spatial disturbances between the forts (ramps, tunnels, shelters) and the different components of these networks (trenches, observatories, artillery positions, etc.). This highlights the impact of these fortifications prior to the WW1, which tended to be obscured by this fundamentally morphogenic conflict. Finally, it questions the resilience of these morphologies associated with the war and the patrimonialization of their ecological (islands of biodiversity), geomorphological (“polemogeomorphosite”) and historical wealth.