Estimation Of Eroded Volume And Retraction Rate In Short-Term On The Barreira Do Inferno Active Seacliff Using Terrestrial Laser Scanner

This article intends to estimate the eroded volume and retraction in short term (six month period) on the Barreira do Inferno active seacliff located on the Eastern Coast of the State of Rio Grande do Norte, based on the use of Terrestrial Laser Scanner (TLS) and point clouds georeferencing with Global Navigation Satellite Systems (GNSS). The seacliff slope scanning was conducted in two occasions, the first on 08/21/2016 (austral winter) and the following on 02/24/2017 (austral summer). The point clouds obtained in these surveys were processed in the softwares CloudCompare, ArcMap, Surfer and Global Mapper for the selection of Digital Terrain Models (DTM) that better represent the features described on the seacliff slope in erosion according to spatial interpolation methods: IDW, NN, Kriging and TIN. In this approach, the seacliff was subdivided into five sectors, of distinct erosive behaviours, for the assessment of DTM performance, quantification of total eroded volume and retraction rate from the comparison between DTM and cross-profiles generated with TLS point clouds. The TIN interpolator method of the CloudCompare and ArcMap softwares was the most suitable for detailed representation of irregularities in the surface and basal incisions in the slope. The methodological strategy also highlighted the relevance of assessing the reliability of the point cloud for the presence of point voids in DTM, due to shadows on TLS scans, and as sources of significant errors in the final calculation of total eroded volume and retraction rate. The results indicated that the active seacliff had an eroded volume of 333 m(3) in the short term and a general retraction of 6 +/- 3.1cm in this period, or 12 +/- 6.2 cm/year. Finally, this study confirms the suitability of using TLS coupled to GNSS, with high precision and accuracy, in obtaining detailed results on the effects of erosion on active seacliffs subjected to the intense coastal dynamics of Northeast Brazil.