LACTOSE - Slow-moving LAndslides in Changing TrOpical landscapes: dynamics and hillslope connectivity from SpacE

Context and objectives

LACTOSE aims to quantify how natural and anthropogenic environmental conditions control the dynamics of slow-moving landslides (SMLs) and their sediment contribution to river systems in changing tropical landscapes. To disentangle the complex influences of environmental changes on SML activity, LACTOSE will analyse hillslope processes across the diverse landscape conditions of the western branch of the East African Rift System (wEARS). This regional-scale approach will be enabled by exploiting synergies between different space-borne remote sensing tools (optical and radar imagery, historical aerial photographs, etc.). LACTOSE is at the interface between natural hazard assessment, geomorphology, land degradation, sediment dynamics, and environmental changes with Earth observation at its core. It is strongly focused on synergies, long-term collaborations, knowledge transfer and capacity building activities with several key research institutions in Africa. 

SO1: To present a first large-scale assessment of the presence of active SML and their spatial variations across a large spectrum of landscape conditions.  
SO2: To quantify and untangle the respective influences of natural (climate, lithology, tectonic settings, etc.) and human-induced (expansion of cultivated and urban land, deforestation) controls on the past and present dynamics of SML.  
SO3: To quantify the potential contribution of SML to river sediment loads by studying their dynamics and connectivity.  

Project outcome

Expected scientific results

To our knowledge, we will be the first to investigate the rates and controls on SML dynamics and their impacts on river systems at such a regional scale in a tropical region. Such a first comprehensive observational study should allow us to better comprehend a) how contrasting and changing environmental conditions affect the occurrence and characteristics of SML in the tropics; b) what are the main controls on the dynamics of SML in tropical mountain region and how SML activity has evolved alongside 70 years of anthropic changes to the landscapes (e.g., deforestation and agricultural terracing); c) what are the overall mobilization rates of SML at the landscape scale, what amount of the sediment transferred to the river systems is due to SML and how did has it changed over time. This is will not only be innovative for better understanding SML processes, but also crucial for improving landslide hazard assessments and our understanding of how environmental changes (anthropogenic and/or natural) affect landscapes and sediment budgets. Finally, this work will help addressing the critical need to better understand Earth-surface processes and their impacts in tropical environments. Capitalising on the results and lessons learned from MODUS, LACTOSE also will also adapt, develop and validate innovative tools and approaches in radar (InSAR/amplitude) and optical space Earth observation and combine them for the first time at an unprecedented regional scale.

Societal and environmental relevance

Although this research project is fundamental in nature, a better understanding of landslide processes and mechanisms is central to landslide hazard and risk assessment.  The information gathered in this project will therefore be used for such assessments in the area and in other regions with similar environmental characteristics. LACTOSE should also improve our understanding of how (anthropogenic and/or natural) environmental changes affect landscapes and sediment budgets – fundamental to assessing human impacts on their environment. Finally, we hope that this work will help to highlight the importance of paying sufficient attention to landslides and other earth surface processes in tropical contexts, where impacts are disproportionately high, but research is too scarce. Through workshops and collaborations with the Université Officielle de Bukavu and the Protection Civile du Sud Kivu, this research project will contribute to the strengthening of research networks in Central Africa.

Expected products and services

• Development of workflows (e.g., based on image correlation and inversion of radar-amplitude images) particularly adapted for the study of landslide dynamics in tropical context – and beyond.

• High-resolution topographic datasets (from UAS and optical remote sensing) useful for other research projects in the area and for local scientists.

• Maps, topographic datasets and inventories will be used for research and teaching purposes in local universities/research centres and are products of potential interest to local authorities involved in disaster risk reduction and land management.

Potential users

•    Researchers involved in landslide and/or remote sensing studies; also including researcher from African institutions based in the region of interest.

•    Maps, topographic datasets, inventories and knowledge will be used for research and education purposes in local universities/research centres and will be products of interest to local authorities (stakeholders, civil protection, etc.) involved in disaster risk reduction and land management.