Mapping gully severity areas using AHP techniques and GIS at Meqebesa sub-catchment, Lake Hawassa watershed, Ethiopia

Gully erosion is a series environmental problem affecting the society. Investigating gully formation factors in a rapidly changing erosion prone are is crucial. Meqebesa sub-catchment in Ethiopia is currently experiencing significant gully expansion. Therefore, this study aims to identify the most influential factors of gully formation and map the severity of gully erosion using field collected data of gully characteristics. Analytical Hierarchy Process (AHP) and geographical information system (GIS) were integrated to select the driving factors among the ten gully influential factors and to map gully erosion severity areas. The predictive performance of the model was validated using field-collected data of gully width and length and an analysis of the area under the curve (AUC). The GIS model achieved 79.17% accuracy in field verification and 68.9% accuracy in the AUC analysis. The overlay analysis showed, land use/land cover to be the most influential factor at 19.2%, followed by rainfall at 13.7%, and slope at 13.2%. Severity mapping revealed 64.72% of Meqebesa sub-catchment is in less severe conditions, while 33.23% is in moderate conditions. The AHP technique reliably identified key gully formation factors influence level in Meqebesa sub-catchment and could hold a potential for transferability to other regions. The gully severity mapping supports the regional planners and managers to draft a mitigation and rehabilitation strategies.