This article presents a set of inundation maps corresponding to flood frequencies of 1%, 2%, 5%, 10%, 20% in the Gianh river basin. The results show that flooding happens more frequent in both river banks and downstream areas of Gianh river basin. As Gianh River runs mainly along Tuyen Hoa District, the communes along the river banks of the district are seriously affected by floods. | Calculating and building inundation maps corresponding to flood frequencies in Gianh river basin