Potential effect of agricultural terraces on landslide occurrence: the tropical mountains of Rwanda

The tropical mountainous environments of the Northern-western provinces of Rwanda in Africa are often referred to as the breadbasket of the country and are also densely populated. This high demographic pressure is associated with significant land management practices. In particular, agricultural practice of terracing has been promoted as soil and water conservation measure on the steep hillslopes of the region. However, the region is also landslide prone and the  potential effect of terracing on landslides occurrence has never been considered in the land management strategy. In this work, we assess this  potential effect through the analysis of more than 4000 recent landslides that were triggered by intense rainfall events. Exploring the role of slope, lithology, regional landslide susceptibility patterns and the types of terraces (typology, age), we show that, overall, terracing increases the odds of landsliding when compared to non-terraced hillslopes. Although the terraces are implemented as soil and water conservation measures in the region, we find that they result into higher hillslope hazard.