Applying a Hand-Held Laser Scanner to Monitoring Gully Erosion: Workflow and Evaluation

Detailed understanding of gully erosion processes is essential for monitoring gully remediation and requires fine-scale monitoring. Hand-held laser scanning systems (HLS) enable rapid ground-based data acquisition at centimeter precision and ranges of 10-100 m. This study quantified errors in measuring gully morphology and erosion over a four year period using two models of HLS. Reference datasets were provided by Real-Time-Kinematic (RTK) GPS and a RIEGL Terrestrial Laser Scanner (TLS). The study site was representative of linear gullies that occur extensively on hillslopes throughout Great Barrier Reef catchments, where gully erosion is the dominant source of fine sediment. The RMSE error against RTK survey points varied 0.058-0.097 m over five annual scans. HLS was found to measure annual gully headcut extension within 0.035 m of RTK. HLS was, on average, within 6% of TLS for morphological metrics of depth, area and volume. Volumetric change over a 60 m length of the gully and four years was estimated to within 23% of TLS. Errors could potentially be improved by scanning at times of year with lower ground vegetation cover. HLS provided similar levels of error and was relatively more rapid than TLS and RTK for monitoring gully morphology and change.

Automated summary

In-depth understanding of gully erosion processes is crucial for monitoring gully remediation efforts, and fine-scale monitoring can be achieved using Hand-held Laser Scanning systems (HLS). The study quantified errors in measuring gully morphology and erosion over a four year period, finding that HLS provided similar levels of accuracy and was relatively faster compared to TLS and RTK. Improvements in error rates could potentially be made by scanning during times of the year with less ground vegetation cover.