This study aims to monitor the changes in dikes and rice crop framing in the Long Xuyen Quadrangle from 2005 to 2018 and estimate the changes in crop seasons inside and outside the dike basin in the Long Xuyen Quadrangle from 2005 to 2018, from which can be used as the foundation for any regional development decisions in the future. The study applied water index method and coastline extraction calculated from LANDSAT imagery to determine the dike condition in the Long Xuyen Quadrilateral and normalized different vegetation index (NDVI) image series using
MODIS imagery to detect rice crop seasons in the period of 2005-2018. The results have determined the changes in crop seasons displayed clearly in areas with dike distribution that mainly cultivated triple rice crop during the period of 2005-2018 had the area increased about 97,472.6 ha. The total area of land cultivated single and double rice crops that adapted to triple rice crop was 87,177 ha, mainly distribution on six districts in An Giang province including Chau Doc, Chau Phu, Chau Thanh, Thoai Son, Tri Ton and Tinh Bien; in four districts of Kien Giang province including Tan Hiep, Hon Dat, Giang Thanh and Chau Thanh; and in Vinh Thanh district of Can Tho city. The research outcome has supported the local authorities in making timely decisions in managing cultivation and regional agricultural
development planning to make use of land effectively.