A two-dimensional analysis of the largest cross-section of earth dams may generate appropriate results provided that the dam is located in a U-shape valley. The Vanyar dam has been constructed in a narrow valley. With regard to the geometrical consideration of the valley, there is no plane strain condition throughout the long side of the dam. In this research, the results of three and two dimensional numerical analyses of the Vanyar dam are compared in terms of settlement, pore water pressure, and total vertical stress. These analyses were carried out by a finite difference method through FLAC-3D and FLAC-2D softwares. In order to verify the results of the analyses, the settlement data recorded by the instruments in the body of the dam are compared to those provided through the numerical analyses. The results of the three and two dimensional analysis show that the settlements in the upper half of the height of the dam have a suitable adaptation. Moreover, the two- dimensional analysis shows the settlements in the lower half of the height of the dam more than those shown by the three-dimensional analysis. Furthermore, in terms of total vertical stress and pore water pressure, the two-dimensional analysis shows the values throughout the height of the dam more than those shown by the threedimensional analysis
