Susceptibility, change and drivers of riverine gullies in an Afromontane agroecosystem

Riverine gully erosion threatens agricultural productivity, infrastructure, water resources, and livelihoods in steep tropical agroecosystems, yet catchment-scale evidence that integrates field-measured gully morphology, susceptibility modelling, temporal change, and community-perceived drivers remains limited. This study assessed the susceptibility, distribution of severity, change, and community-perceived drivers of riverine gully erosion in the Lwakhakha sub-catchment of eastern Uganda. The geometries of 25 gullies were measured using Real-Time Kinematic (RTK) positioning, and geocoded gully locations were integrated with soil characteristics, slope, elevation, geology, rainfall, and Normalised Difference Vegetation Index (NDVI) datasets. A total of 380 households were randomly selected and interviewed using semi-structured questionnaires. The results of this study revealed that gully erosion occurred across three severity classes (high, moderate, and low), with gullies occupying a total area and volume of 209,116 m 2 and 260 m, respectively. The best predictors of riverine gully erosion were slope, elevation, and NDVI. Changes in gully erosion indicated that gullies are actively increasing in both area and volume, and the perceived major drivers were slope steepness, erratic rainfall, soil type, weak underlying geology, absence of vegetation cover, deforestation, poorly constructed roads, and the land tenure system ( P < 0.05). Community responses identified interacting physical, economic, and social drivers, particularly slope steepness, intense rainfall, soil and geological conditions, vegetation loss, deforestation, road drainage, poverty, and land-tenure constraints. The combined evidence indicates that gully erosion in the Lwakhakha sub-catchment is a coupled hydro-geomorphic and socio-environmental process. Interventions should therefore prioritise the upper and middle sub-catchments and combine runoff control, vegetation restoration, road drainage management, sustainable land management, and locally appropriate livelihood and tenure measures.