Drought Mapping in Lembata Regency with the Normalized Difference Drought Index (NDDI)
Abstract
Drought is an event that threatens and disrupts human life as it is closely related to the availability of groundwater reserves. The availability of clean water has become a serious challenge due to arid climate conditions, low rainfall, and prolonged dry seasons. Ileape Timur Sub-district, Ileape Sub-district, and Nubatukan Sub-district in Lembata Regency are characterized by coastal, hilly, and mountainous topography. Given this topographic condition, these three sub-districts are experiencing both clean water crises and land drought. Therefore, this study aims to identify the spatial distribution of land drought using the Normalized Difference Drought Index (NDDI) algorithm by utilizing Sentinel-2A satellite imagery from 2025. The results show that Ileape Timur, Ileape, and Nubatukan Sub-districts are predominantly categorized as severely drought-affected, covering an area of 29,622.343 hectares (90.58%), and extremely drought-affected, covering 1,695.109 hectares (5.18%). This condition is largely due to the dominance of shrub vegetation with moderate vegetation density and non-water body Wetness levels. Based on field validation using a confusion matrix, the study achieved an Overall Accuracy of 92.59% and a Kappa Accuracy of 87.42%. The findings of this research are expected to contribute to mitigating future drought hazards in Lembata Regency.
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