LiDAR, UAV SfM and geomorphic change detection in small quarry and landslide interactions

<p>Quarry activity triggers landslides, especially in small, unplanned, and not maintained quarries. Given the size of these small quarries that are very frequent in the rural areas of north-eastern Romania, their study is difficult because of the lack of topographic data. We show the usage of remote sensing data for geomorphic change detection, which is able to reveal the topographic evolution of the quarrying and landsliding. Legacy LiDAR data from 2012 and field surveyed UAV from 2019 are used to assess the topographic changes, compared to the 1980 5k topographic maps. The quarry location is related to the presence of old landslide bodies (dated to the early medieval period using radiocarbon ages of soil organic matter fractions), from which the clay material is excavated for various construction projects. The unplanned excavation reactivated the body of an old landslide that will continue evolving. The usage of LiDAR data and the UAV SfM survey allowed us to derive 0.25 m DEMS that pinpoint the volumetric change of the quarried material and of the landslide reactivation. As a future prospect, the use of such remote sensing data can pinpoint areas where these unplanned quarries could affect the stability of the hillslopes and become a hazard.</p>

A comparison of Structure from Motion Photogrammetry and the Traversing Micro Erosion Meter for measuring erosion on rock shore platforms

For decades researchers have used the Micro Erosion Meter and it successor the Traversing Micro Erosion Meter to measure microscale rates of vertical erosion (downwearing) on rock shore platforms. Difficulties with upscaling of microscale field data in order to explain long term platform evolution have led to calls to introduce other methods which allow measurement of platform erosion at different scales. Structure from Motion Photogrammetry is fast emerging as a reliable, cost-effective tool for geomorphic change detection, providing a valuable means for detecting micro to meso-scale geomorphic change over different terrain types. Here we present the results of an experiment where we test the efficacy of Structure from Motion Photogrammetry for measuring change on rock shore platforms due to different erosion processes (sweeping abrasion, scratching and percussion). Key to this approach is the development of the Coordinate Reference System used to reference and scale the models, and which can be easily deployed in the field. Experiments were carried out on three simulated platform surfaces with low to high relative rugosity to assess the influence of surface roughness. We find that a Structure from Motion Photogrammetry can be used to reliably detect micro (sub mm) and meso (cm) scale erosion on shore platforms with a low Rugosity Index. As topographic complexity increases, the scale of detection is reduced. We also provide a detailed comparison of the two methods across a range of categories including cost, data collection, analysis and output. We find that Structure from Motion offers several advantages over the Micro Erosion Meter, most notably the ability to detect and measure erosion of shore platforms at different scales.