Investigation of Low Frequency Debris Flow Gully in Dense Forest Area on Airborne LiDAR Technology

Airborne LiDAR is an active scanning remote sensing technology. Its laser pulse signal can partially pass through the gap of multi-layer vegetation to the surface, and quickly obtain high-precision three-dimensional data and images of the surface after stripping the vegetation layer, so as to truly depict the landform contour and finely restore the surface features. The low-frequency debris flow gully has a long intermittent period and the surface vegetation is relatively lush. The commonly used remote sensing technologies such as optical image and InSAR have certain limitations on its interpretation. The pilot work of airborne LiDAR was carried out for the detailed investigation of geological disasters in Yantian District. The surface DEM data with a resolution of 0.2 m was extracted, and the fine mountain shadow image was generated. The remote sensing interpretation mark of debris flow airborne LiDAR image was preliminarily established. On this basis, 17 gullies were interpreted, and finally 4 low-frequency debris flow gullies were determined. Combined with the DEM image of airborne LiDAR, the morphological characteristics and material source distribution of debris flow gullies were investigated in detail, and the present activity of debris flow gully was preliminarily analyzed. Practice has proved that in areas with high vegetation coverage, the interpretability of airborne LiDAR images is significantly better than that of traditional optical remote sensing, and is suitable for early identification and follow-up investigation of hidden dangers of geological disasters such as debris flow.