Interactions between deforestation, landscape rejuvenation, and shallow landslides in the North Tanganyika–Kivu rift region, Africa

Abstract. Deforestation is associated with a decrease in slope stability through the alteration of hydrological and geotechnical conditions. As such, deforestation increases landslide activity over short, decadal timescales. However, longer timescales (0.1–10 Myr) location timing landsliding controlled by interaction between uplift fluvial incision. Yet, (human-induced) landscape evolution has hitherto not been explicitly considered. We address this issue North Tanganyika–Kivu rift region (East African Rift). In recent decades, regional population grown exponentially, expansion cultivated urban land resulted widespread deforestation. past 11 Myr, active continental rifting tectonic processes have forged two parallel mountainous shoulders that are continuously rejuvenated (i.e., actively incised) knickpoint retreat, enforcing topographic steepening. order to link rejuvenation erosion, we compiled an inventory nearly 8000 shallow landslides © Google Earth imagery from 2000–2019. To accurately calculate erosion rates, developed new methodology remediate biases linked spatial temporal inconsistency satellite imagery. Moreover, account for impact rock strength on both occurrence limit our analysis types threshold angles 24–28?. Rejuvenated landscapes were defined as areas draining towards Lake Kivu or Tanganyika downstream retreating knickpoints. find rates these roughly 40 % higher than surrounding relict landscapes. contrast, exerts stronger control These results reconciled observation generally gradient relief average steeper The weaker effect steepness could be result three factors: absence earthquake-induced events inventory, thinner regolith mantle, drier climate. More frequent extreme rainfall landscapes, presence thicker regolith, may explain response compared Overall, initiates peak lasts approximately 15 years factor 2 8. Eventually, deforested falls back level similar observed under forest conditions, most likely due depletion unstable regolith. Landslides only more abundant but also smaller size, which again consequence mantle and/or seismic fractures bedrock reduces minimal critical area failure. With paper, highlight importance considering geomorphological context when studying use changes activity.