Recently, Unmanned Aerial Vehicle (UAV) based communications systems have attracted increasing research and commercial interest due to their cost effective deployment and ease of mobility.During natural disasters and emergencies, such networks are extremely useful to provide communication service. In such scenarios, UAVs position and trajectory must be optimal to maintain Quality of Service at the user end. This paper focuses on the deployment of an SDN-based UAV network providing communication service to the users. We consider the deployment of the system in stadiums and events. In this paper, we propose a scheme to allocate UAVs to the users and a traffic congestion algorithm to reduce the number of packets dropped to avoid re-transmissions from the user end. We also propose an energy efficient multi hop routing mechanism to avoid the high power requirement to transmit longer distances. We assume that all the back-haul links have sufficient capacities to carry all the traffic from the front-haul links and the design of UAVs must consider their power requirements for both flight and transmission.