Evaluation of the change in crop structure under the impact of flood prevention dikes in the Long Xuyen Quadrangle in the period 2005-2020

The study was conducted to monitor spatial fluctuations of dikes affecting the rice crop structure and evaluate changes in rice crop structure inside and outside the dikes in the Long Xuyen Quadrangle in the period 2005-2020. That serves as a basis for assessing the current status of flood control and the changing trend of rice production in the region in the future. The study uses LANDSAT images and applies the normalized difference water index (NDWI) and shoreline extraction to determine the current condition of dikes in the Long Xuyen Quadrangle region, while combining a series of normalized difference vegetation index (NDVI) on moderate resolution imaging spectroradiometer (MODIS) image data to determine the structure of rice crops in 2005 and 2020. The results show that the embankment length increased by 1,910.15 km compared to 2005 and the natural embankment area increased to 123,020.31 ha (accounting for 24.63% of the area’s natural area) in the period 2005-2020. The farming system in the study area impacted by flood prevention dike changes from other crops to triple-rice crop cultivation. Specifically, the total area of the other cultivation types converted into triple-rice crop cultivation is 90,904.77 ha, accounting for 51.92% of the total area of structural transformation of farming types, concentrated in districts with large dike areas such as Thoai Son, Chau Phu, and Chau Thanh districts (An Giang province). The research results contribute to supporting environmental management and orienting rice production trends in the region in the future.