Landslides in Belgium—Two case studies in the flemish ardennes and the pays de herve

Abstract

Most landslides in Belgium, and especially the largest features, do not occur in the Ardenne, where the relief energy and the climate conditions seem most favourable. They appear in regions located mainly north of them where the lithology consists primarily of unconsolidated material. They develop on slopes that are relatively smooth, and their magnitude is pretty large with regard to that context. An inventory of more than 300 pre-Holocene to recent landslides has been mapped. Twenty-seven percent of all inventoried landslides are shallow complex landslides that show signs of recent activity. The remaining landslides are deep-seated features and rotational earth slides dominate (n > 200). For such landslides, the average area is 3.9 ha, but affected areas vary from 0.2 to 40.4 ha. The exact age of the deep-seated landslides is unknown, but it is certain that during the last century no such landslides were initiated. Both climatic and seismic conditions during the Quaternary may have triggered landslides. The produced landslide inventory is a historical inventory containing landslides of different ages and triggering events. Currently, only new shallow landslides or reactivations within existing deep-seated landslides occur. The focus on the Hekkebrugstraat landslide in the Flemish Ardennes allows us to understand the recent dynamics of a large reactivated landslide. It shows the complexity of the interactions between natural and human-induced processes. The focus on the Pays the Herve allows for a deeper understanding of landslide mechanisms and the cause of their origin in natural environmental conditions. These two examples are among the best-studied landslides and their analysis allows us to highlight the main processes at play and to better unravel their interactions.