A risk analysis framework for transmission towers under potential pluvial flood - LiDAR survey and geometric modelling

The failure of transmission towers often causes widespread blackouts and results in electrical shock to people and animals via water bodies especially in areas prone to river floods and storm surges. To ensure safety operation of the power networks, the structural health of transmission towers should be maintained and investigated under the potential of flood hazards. We propose a comprehensive risk assessment framework for the transmission towers affected by the pluvial flood, based on the geometry of the tower and the terrain. The geometry is first obtained from 3D point clouds derived from airborne Light Detection And Ranging (LiDAR). The framework consists of a series of new point cloud segmentation and fitting algorithms, designed to accurately estimate the inclination angles of the transmission towers. In addition, the framework includes an existing flood risk index (Topographic Control Index, TCI) and a new risk index for the transmission towers (Transmission Tower Risk Index, TTRI) which reflects the risk for tower damages under the pluvial flooding. The framework is applied to Hengman, situated on the Pearl River estuary, Southern China. Based on our results, high TTRI were shown to be often associated with high flooding risk. This coincides with our hypothesis that the floods weaken foundation settlements and thus trigger tower inclinations. The TTRI and TCI analyses reveal that 8 towers out of similar to 60 in total are with low-risk (13.8%); 2 with medium-risk (3.5%) and 1 tower is at high-risk. The total area affected by the risk tower is similar to 2.7 km(2), accounting for 5.5% of the study area. The results suggested that the proposed framework is implementable and reliable. The resultant analysis can help decision makers to pinpoint the affected transmission towers along with the peripheral affected areas for precaution.