LoRaWAN as a low cost and has a wide area coverage is an efficient technology to replace a lot of manual processes. This paper presents simulation results of the usage of LoRaWAN for flood early warning control system in Ciliwung River. Ciliwung River is one of the rivers that flow through Jakarta, the capital city of Indonesia. One of the main causes of floods in Jakarta is the increase in the Ciliwung River water discharge due to high rainfall in the upstream area and areas along the Ciliwung River. Flood early warning control system, is an important factor for the Jakarta provincial government to determine decisions on flood mitigation, for example the preparation of evacuation areas, water pumps and floodgate capacity. Based on water level measurement points on existing systems, we try to measure the exact distance and height to determine the gateway placement. The area of water measurement points is divided into 2 areas, namely area 1 that covers Bogor and area 2 that includes Depok and South Jakarta. The simulation shows that the use of 1 gateway with antenna height of 30 meters in area 1 and 1 gateway with antenna height of 108 meters in area 2 can cover all end devices. In area 2, using 2 gateways with a height of 30 meters each can cover all end devices with a much lower gateway height.