The Four Major River Restoration Project in South Korea contributes to solving flood damages and water shortages. It purpose is for the rehabilitation of water ecosystems, providing more cultural leisure activities and spaces, and improving peoples' quality of life by inducing water quality improvements and river restorations. As part of the project, it is necessary to monitor a variety of data collected in and around the rivers, covering an area of over 240 miles in length. There are currently more than 200 MIMO and non-MIMO mesh nodes deployed along with 300 cameras to support the sensor and video surveillance applications, which is believed to be one of the biggest mesh network projects in the world. In the process of network construction, we focused on investing and securing the least expensive data services possible despite the harsh surroundings in the project area. To do this, transmission environment analysis was performed such as LOS(Line of Sight) tests, reception level analysis, and transmission speed measurement to provide safe services. Reception level in all places was measured between −55 dBm to 70 dBm, and data transmission speed was proven to be more than 20 Mbps. This means that problems such as the slow or delayed transmission speed of the existing network and blanket areas could be overcome by WMN. In addition, through the network management system, dual installed mesh network can have much higher availability, reducing the possibility of losing any river monitoring data. It also shows the possibility that a wireless mesh network could be extended to national infrastructure even with tough environmental conditions.