Zapico, I., Molina, A., Laronne, J. B., Castillo, L. S., Duque, J. F. M. (2020). Stabilization by geomorphic reclamation of a rotational landslide in an abandoned mine next to the Alto Tajo Natural Park. Engineering Geology 264 DOI: 10.1016/j.enggeo.2019.105321
Two abandoned kaolin mines, surrounding one of the most outstanding natural parks of Spain, the Alto Tajo, have caused frequent environmental impacts. Within these are unstable areas prone to extensive mass movements that influence off-site sediment dynamics over the fluvial system. A waste dump in the Nuria mine obstructing a stream in the center of a valley experienced a rotational landslide. Mass movement between 2012 and 2014 was 0.025-0.026 m day(-1). To mitigate the high risk of an earthflow, a novel stabilizing surface drainage technique was implemented. Two remedial valleys designed with fluvial channels were constructed surrounding the landslide main body using natural landform design and regrading, with no need for artificial materials such as concrete or piles. This novel remediation process is generically termed geomorphic reclamation. The specific method applied to this site was GeoFluv with Natural Regrade software. Before (2014) and after geomorphic stabilization (2015-2017), the landslide was monitored using Digital Elevation Models (DEMs) of Difference (DODs) obtained by a Geomorphic Change Detection (GCD) tool. Two modem techniques, Terrestrial Laser Scanning (TLS), and, Structure from Motion photogrammetry combined with an Unmanned Aerial Vehicle (SfM-UAV), were used to acquire High-Resolution Topographies (HRTs) from which DEMs were derived. Data analysis and field monitoring results demonstrate that: i) the Nuria mine transformed almost 50% of the upper part of a natural catchment; ii) a waste dump active landslide with a surface rupture < 15m posed a high-risk hazard due to its continuous advance; iii) geomorphic reclamation succeeded in stabilizing the landslide during the monitoring period; iv) SfM-UAV-based topographies offer better accuracy and higher resolution, are cheaper and are obtained faster than TLS for mine areas.