A Multi-Criteria Assessment of Drought Hazard in the Lake Toba Catchment Area Using AHP and GIS

Abstract

Drought in the Lake Toba catchment area has become an increasing concern due to climate change and land-use change. This study assessed and mapped drought hazard across 46 sub-districts in the Lake Toba catchment area, North Sumatra, using the Analytic Hierarchy Process (AHP) integrated with Geographic Information Systems (GIS). Five parameters were evaluated: rainfall, land use, distance to water sources, soil type, and slope. AHP weighting shows that rainfall is the most influential factor (36%), followed by land use (21%), water sources (20%), soil type (13%), and slope (10%). Spatial overlay analysis classified drought hazard into low, medium, and high categories. The results indicate that 29,394 ha (11%) of the area fall into the high-hazard class, 178,013 ha (68%) into the medium-hazard class, and 55,499 ha (21%) into the low-hazard class. High drought hazard is concentrated mainly in the eastern and southern parts of the catchment. Lumbanjulu, Muara, Siborong-Borong, and Silaen sub-districts each contain more than 2,000 ha of high-hazard area. These findings provide a useful basis for drought mitigation, land-use planning, and water resource management in the Lake Toba region.