Compounding landslides and flash floods in tropical East Africa: A remote sensing perspective

Flash floods occur worldwide. Triggered by intense rainfall spanning only a few hours, they frequently occur together with landslides. These landslides can deliver hillslope material to the river system, leading to amplified and devastating impacts. Landslides and flash floods are influenced by the daily to monthly variations in rainfall that precondition the landscape and change their likelihood of occurrence. The cooccurrence, interaction, and the preconditioning effect of rainfall reflects the compounding nature of these hazards. The tropics provide favorable conditions for their occurrence, with inequalities and challenging socioeconomic conditions often increasing their impact. Understanding their occurrence is therefore essential. In this PhD research, we aim to better understand the spatial and temporal patterns of landslide and flash flood events in the tropics. To do this, we focus on the western branch of the East African Rift (WEAR). We developed two complementary remote sensing methodologies that  allow for the detection of landslide and flash flood events in the challenging data scarce conditions of the tropics. Through these methodologies we have identified more than a hundred new landslide and flash flood events in the WEAR. Our results suggest that preconditioning rainfall plays a central role in understanding their occurrence, along with land use and land cover and landscape geological history. This research offers new information and tools relevant to a region that is commonly underrepresented in global studies, and that can serve as a foundation for further landslide and flash flood research.