With the recent growth in wireless communication, non-orthogonal multiple access (NOMA) plays an essential role in the 5G network. In the event of natural disasters protecting the life of peoples has been playing an important role around the world. Natural disasters cannot be bypassed, but their effect can be mitigated by a comprehensive network model of the disaster management system. In this paper, an unmanned aerial vehicle (UAV) and ad-hoc NOMA-BS can be applied for serving the ground users in a non-functional area (NFA) or disaster area. Disaster areas can be divided into two, such as wide area and confined area. However, a UAV can communicate to ground users based on line-of-sight (LoS) and non-line-of-sight (NLoS) in a wide area using a scheduling approach. Also, an ad-hoc NOMA-BS can serve NOMA signal to ground users in a confined area. Furthermore, a mode selection algorithm can be applied for the users to determine whether they are nearer to UAV and ad-hoc NOMA BS or not. The expression for coverage probability and average rate are developed in our proposed UAV-assisted NOMA network. The outage probability, coverage probability, and average rate are investigated for several network parameters. Finally, results are shown via simulation in MATLAB.