In recent years, the use of IoT networks for environmental data collection by local governments has been increasing. However, these networks face a critical issue: when relay points are lost due to disasters, most communications are disrupted. In this study, we propose a system that utilizes Low Power Wide Area (LPWA) communication technology to autonomously reconstruct communication networks. The proposed system employs a tree-structured LPWA network that dynamically reconfigures itself in the event of a failure. Specifically, each node assesses the health of its upstream node based on relayed uplink packet information and dynamically selects an optimal alternative route. We evaluate the effectiveness of our method through field experiments, confirming that network prevention can be appropriately performed even in the presence of node failures.