The two dimensional dam break problem for wet bed case is investigated. The leading order and the second order problem are stated in nondimensional form. Solution to the leading order problem by using three different methods is given and explained in detail. Both Fourier series method and Galerkin method have difficulties on its own because of the singularity at the triple point. Although the singularity is ignored in Galerkin method, the method does not work except for the interface. Thus conformal mapping techniques is preferred because of the convenience and the strength of the complex analysis. The velocity profiles at whole boundary are obtained by using this conformal mapping. The second order solution of velocities are also obtained by using the same conformal mapping. On the other hand, the domain decomposition method (DDM) is applied for the second order dam break problem of dry bed case. The leading order solution helped to determine the suitable parameters for DDM. The leading order and second order solution of the free surfaces give a more realistic shape using the Lagrangian solution at the upper corner point. We assume this work contains useful and applicable methods in it for gravity driven flows and it will wake up different perspectives in readers mind.