Monitoring and Early Warning the Debris Flow and Landslides Using VHF Radar Pulse Echoes From Layering Land Media

To monitor debris flows and landslides, geologic surveying has been usually implemented to ascertain where these natural hazards might happen. These traditional observations at discrete sites are very restrictive in both temporal and spatial scales, and cannot make accurate and timely decision for early warning of geologic disaster occurrences. In this letter, very high frequency (VHF; ~100 MHz) pulsed radar is proposed as a monitoring tool to probe the layering land media. Due to large penetration depth of VHF radar on the order of tens of meters, radar echoes can detect the change of water content underneath ground surface, which is an essential stimulator to cause the debris flow and landslides. A model of layering land media embedded by random scatterers (stone or water) with randomly rough interfaces is presented, and polarimetric radar range profiles from underground structures under different situations are numerically simulated. Results show that distinct features in radar range profiles can be directly attributed to underground water content change and/or water distribution. The proposed VHF radar seems promising for early warning of geologic hazards. The differences of radar images between the normal day and warning days, e.g., after severe storm, can be used to predict potential occurrence of debris flow or landslides.