Using Landsat Satellite Data to Explore Drought Index during the Dry Season Period 1990–2024 in Thu Duc City of Ho Chi Minh City, Vietnam

Drought is among the most significant natural disasters globally, caused by prolonged rainfall deficits that result in precipitation levels significantly below the long-term average. It has far-reaching impacts on the environment, economy, and society, including reduced agricultural productivity, diminished arable land, and socio-economic challenges. In recent years, remote sensing has emerged as a powerful tool for drought monitoring and mapping, offering significant advantages in spatial and temporal analysis. This study aimed to assess drought trends in Thu Duc City, Ho Chi Minh City, Vietnam, during the dry seasons from 1990 to 2024 using Landsat satellite data processed on the Google Earth Engine platform. The Normalized Difference Drought Index (NDDI), derived from the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Water Index (NDWI), was utilized to quantify drought severity. The results indicate a substantial increase in drought-affected areas over the study period, particularly after 2000, with drought severity closely linked to El Niño-Southern Oscillation (ENSO) cycles. Areas with low vegetation and water content were most vulnerable to high drought levels, as reflected in NDDI values. Notably, the northern and southern regions of Thu Duc City exhibited frequent drought occurrences, while areas with dense vegetation and abundant water resources, such as the eastern parts, were less affected. To further validate these findings, a land cover classification provided the relationship between drought-prone areas and different land cover types, highlighting the role of urban expansion and vegetation loss in increasing drought susceptibility. Urbanized areas exhibited higher drought intensity, whereas regions with substantial green cover and water bodies showed lower drought impact. Future studies should collect more field data to enhance the reliability of drought assessments. Expanding the temporal and spatial scope and examining socio-economic impacts will provide a more comprehensive understanding of drought dynamics. These findings underscore the importance of remote sensing in supporting sustainable urban planning and resource management in newly established urban areas as Thu Duc City.