Paz Fernandez

A new technique for the detection of large scale landslides in glacio-lacustrine deposits using image correlation based upon aerial imagery: a case study from the French Alps

Abstract Landslide monitoring has benefited from recent advances in the use of image correlation of high resolution optical imagery. However, this approach has typically involved satellite imagery that may not be available for all landslides depending on their time of movement and location. This study has investigated the application of image correlation techniques applied to a sequence of aerial imagery to an active landslide in the French Alps. We apply an indirect landslide monitoring technique (COSI-Corr) based upon the cross-correlation between aerial photographs, to obtain horizontal displacement rates. Results for the 2001–2003 time interval are presented, providing a spatial model of landslide activity and motion across the landslide, which is consistent with previous studies. The study has identified areas of new landslide activity in addition to known areas and through image decorrelation has identified and mapped two new lateral landslides within the main landslide complex. This new approach for landslide monitoring is likely to be of wide applicability to other areas characterised by complex ground displacements.

GIS environmental information analysis of the Darro River basin as the key for the management and hydrological forest restoration

This article presents analyses of soil and environmental information for the Darro River basin (Granada-Spain) preliminary to its hydrological and forestry restoration. These analyses were carried out using a geographical information system (GIS) and employing a new procedure that adapts hydrological forest-restoration methods. The complete analysis encompasses morphological conditions, soil and climate characteristics as well as vegetation and land use. The study investigates soil erosion in the basin by using Universal Soil Loss Equation (USLE) and by mapping erosion fragility units. The results are presented in a set of maps and their analysis, providing the starting point for river basin management and the hydrological and forestry-restoration project that was approved at the end of 2015. The presence of soft substrates (e.g. gravel and sand) indicates that the area is susceptible to erosion, particularly the areas that are dominated by human activity and have little soil protection. Finally, land use and vegetation cover were identified as key factors in the soil erosion in the basin. According to the results, river authorities have included several measures in the restoration project aimed at reducing the erosion and helping to recover the environmental value of this river basin and to include it in recreation possibilities for the community of Granada. The presented analytical approach, designed by the authors, would be useful as a tool for environmental restoration in other small Mediterranean river basins.

2D Horizontal Landslide Displacement Estimation by Multi-temporal Image Correlation Techniques

Geomatic techniques based on digital images have become a very useful tool for landslide monitoring, quantifying landslide movements over a long period of time. One of these techniques is based on digital image correlation. Digital image correlation estimates 2D displacements by means of statistical techniques, automatically matching identical points in the two digital images. It may be applied using remote sensing or aerial images. Digital image correlation has been applied to multi-temporal aerial photographs at the Cerro Gordo landslide (Granada, Spain) which is badly affecting an urbanized area. This landslide consists of a main deep slide and several minor shallow slides, located around the head scarp or affecting some parts of the main landslide body. Slides involve existing landfills used for urban works as well as in situ materials (colluvial deposits and weathered schists). The period under study (2002–2010) has been divided into four subperiods of approximately two years each. Results provide horizontal displacement in the landslide area and surroundings which allow to assess the landslide movement evolution at different stages according to triggering factors and structural measures that were carried out to stabilize the affected area. Over the period of 2002–2004, displacement rates varied from 2 to 6 cm, meanwhile for the periods of 2004–2006 and 2006–2008 displacements continued with 4–6 cm rates. Then, the period of 2008–2010 generally shows a higher activity with more areas showing 6 cm displacement rates. Surface observations of these periods go along with both location and direction of displacements as shown by the results of digital image correlation techniques. Image correlation results have provided very useful information to understand the complex movements of the landslide as well as the effectiveness of the structural measures implemented.

The Calaiza landslide on the coast of Granada (Andalusia, Spain)

The Costa Tropical in Granada Province, in Southern Spain, was intensively developed during the 1980s and 90s. A complex of several residential communities was built on the eastern slope of the coastal Cerro Gordo hill (Almuñécar), on the pre-existing Calaiza landslide. This was not identified in the preliminary technical studies, thus giving rise to a set of incidents associated with this unforeseen unstable slope. To ensure sea views from all the houses, excavations and fillings were carried out, creating a stepped slope, on which the new foundations of structures and roads were located and subsequently damaged by an increasing number of cracks and deformations, leading to 42 houses becoming ruins in the period 2003–2016. Since 1990, annual and monthly rainfall has been variable in the area, and some rainfall peaks were eventually associated with damage proliferation, although more frequently damage was recorded during dry or low rainfall seasons, when water infiltrated from breaks in pipelines. This damage results from a combination of sliding and bad construction practices at increasing rates from dry to humid periods or during heavy rains. An overall perspective of the geotechnical and geomorphological features of the study area, the landslide reactivation, and its correlation with the damage evolution, as well as its legal consequences, is presented here.

Slopes geometric model

Geometric constraints impose one of the limiting factors in successfully applying the DInSAR technique in hilly areas. These limitations are related to the combination of SAR-image characteristics, due to the incidence angle of the sensor during the acquisition, and the properties of the orientation and slope angle. Consequently, a Pre-DInSAR geometric analysis is highly recommended to detect the areas where the DInSAR technique will be feasible. This previous phase implies some GIS software processes. To simplify this process and avoid human errors, we have developed an automatic model created with Model Builder ArcGIS software. This paper presents the model as well as an example of its application to an area previously analysed manually in order to validate the model. This pre-DInSAR analysis could increase the success of DInSAR studies and eliminate possible wrong justifications in the areas in which DInSAR results are unfeasible. Slope geometry limits the success of DInSAR technique application in hilly areas.A geometric analysis prior to applying the DInSAR technique helps to detect areas where it will be feasible.We present a model developed to automatize and simplify the geometric considerations and avoid human errors.The model developed is effective, quick and easy: a DEM and a few minutes are needed to select DInSAR application areas.

Teaching methodologies to promote creativity in the professional skills related to optics knowledge

We present the methodologies proposed and applied in the context of a teaching-innovation project developed at the University of Granada, Spain. The main objective of the project is the implementation of teaching methodologies that promote the creativity in the learning process and, subsequently, in the acquisition of professional skills. This project involves two subjects related with optics knowledge in undergraduate students. The subjects are “Illumination Engineering” (Bachelor’s degree in Civil-Engineering) and “Optical and Optometric Instrumentation” (Bachelor’s degree in and Optics and Optometry). For the first subject, the activities of our project were carried out in the theoretical classes. By contrast, in the case of the second subject, such activities were designed for the laboratory sessions. For “Illumination Engineering” we applied the maieutic technique. With this method the students were encouraged to establish relationships between the main applications of the subject and concepts that apparently unrelated with the subject framework. By means of several examples, the students became aware of the importance of cross-curricular and lateral thinking. We used the technique based on protocols of control and change in “Optical and Optometric Instrumentation”. The modus operandi was focused on prompting the students to adopt the role of the professionals and to pose questions to themselves concerning the practical content of the subject from that professional role. This mechanism boosted the critical capacity and the independent-learning ability of the students. In this work, we describe in detail both subject proposals and the results of their application in the 2011-2012 academic course.

Reflectance of interurban-road pavements from radar-based measurements

Reflectance measurements in interurban-road typical pavements are essential for traffic security. The reflectance of interurban-road pavements presents high variability due to such variables as climatic and atmospheric conditions and the presence of foreign materials on the road (e.g. dirt, fuel or oil). For this reason, the recording of real-time measurements for these kinds of pavements is a complex task. However, its critical importance in traffic safety demands precise measurements under all the possible conditions. In this context, the use of remote-sensing systems working in the radar spectral range is of great interest. With active sensors that receive their own radar signal, the reflectance measurements made by the remote-sensing system are not influenced by the atmospheric conditions. In this work, we present a radar-based methodology to develop real-time measurements of the reflectance in typical interurban-road pavements. We are engaged in extending this new method to study the reflectance of interurban-road pavements within the visible spectrum.