© 2018 IEEE. In this paper, we propose a group-based scheduling method in dense wireless sensor networks for detection of landslide area. In order to collect information of the entire landslide area, sensor nodes which detect landslides need to send it to nodes outside the area before they become orphaned from the network. To this end, the proposed method first groups sensor nodes into the special groups in advance, which consist of nodes that do not interfere each other and are located spatially uniform. On detecting landslides, sensor nodes broadcast packets that contain the landslide information in order for each pre-scheduled group while mitigating network congestion by means of duplicate packet reduction and packet aggregation techniques. Simulation results show that the proposed method achieves an average packet reception ratio of about 90% from nodes in landslide area within 1.3 seconds after the landslide occurs, regardless of landslide's size.