Influence of inherited topography on gravitational slope failure: three‐dimensional numerical modelling of the La Clapière slope,Alpes‐Maritimes,France

Gravitational slope failure involves rock slopes at various scales. Nowadays, it is accepted that different factors influence slope destabilization, including topography. In many cases, slope failure occurs between tributary valleys cutting the slope. In this study, we ask what influence tributary valleys have on slope failure. To tackle this question, we developed a 3‐D numerical model of the La Clapière Slope and then examined a series of simplified 3‐D models with different geometries of tributary valleys (spacing and depth). Our results show that: (1) whatever considered in situ stresses are, including the third dimension reduces the destabilization threshold compared with 2‐D models; and (2) the spacing and the depth of tributary valleys influence slope failure. For shallow incisions, increasing the lateral spacing between tributary valleys does not affect failure localization but does increase slope damage (to a stable value from 2000 m). However, deeper incision does not affect slope damage but does contribute to failure localization. When the spacing is less than 1500 m, the part of the slope between tributary valleys is not involved in the failure process, but for spacings above 1500 m slope failure occurs between tributary valleys.