Long-Term Flood Inundation Trends and Their Effects on Diverse Agricultural Systems in Ben Tre of Vietnam

Abstract

The Vietnamese Mekong Delta (VMD), a critical agricultural hub, faces recurrent flooding that poses substantial threats to livelihoods and productivity. Ben Tre province, with its low-lying coastal terrain, is particularly vulnerable. Effective risk management and sustainable agricultural development necessitate a thorough understanding of these flood dynamics. This study leveraged the Google Earth Engine (GEE) platform and Sentinel-1 Synthetic Aperture Radar (SAR) imagery to analyze flood inundation patterns and their impacts on diverse agricultural land uses in Ben Tre province from 2015 to 2023. The methodology involved SAR data pre-processing, Otsu thresholding for water body delineation from VH polarization data and change detection using a 2020 land use map to quantify annual flooded areas and their impact on specific agricultural categories. The total inundated area peaked in 2018 at 58,334 ha, a significant increase from 27,934 ha in 2015, before stabilizing around 42,000–44,000 ha in 2021–2023. Flooded agricultural land mirrored this trend, increasing from 18,615 ha (2015) to a peak of 39,514 ha (2018), then decreasing to 28,841 ha (2023). Notably, wet rice cultivation experienced a 37.8% increase in its flooded area over the study period, while other annual crops and perennial crops saw increases of 38.9% and 68.4%, respectively. This research demonstrates the GEE platform's efficacy with Sentinel-1 SAR for robust, long-term flood monitoring and impact assessment, revealing escalating flood pressure on key agricultural systems and an expansion of flooding beyond traditional low-lying zones, providing crucial data for adaptive land use planning.