Historical morphological changes (1956-2017) and future trends at the mouth of the Ebro River delta (NE Spain)

The present work focuses on the recent morphological changes recorded in the Ebro River delta, by using aerial photographs in the last six decades and by analyzing changes in the main constitutive features through geomorphological maps. Geomorphological maps of the years 1956 and 2017 are here presented. The results obtained give very valuable clues about the recent trends of the river delta mouth, which can be used to predict future coastal changes to be expected in the following decades. In this sense, by analysing changes in the surface by means of the geomorphological maps together with a shoreline analysis, a differential behavior has been described at both sides of the river mouth: the left side, El Garxal wetland, shows an accretionary trend with rates reaching +40 m/year, while the right side, San Antonio Island, shows erosive trends of more than -20 m/year. This last side also presents a surface reduction of more than 50 ha in the last 60 years. These results suggest that, approximately by the year 2050, the emerged San Antonio Island may disappear if shoreline retreat trends are maintained, making El Garxal exposed to easterly storms, the main erosive dynamic processes in this zone and, therefore changing the entire configuration of the Ebro River delta mouth in the upcoming years. Despite possible solutions have been described in recent works, they may not contribute to a total recovery of the most natural part of the Ebro Delta. Urgent management plans are required to attempting to slow or reverse these trends, otherwise one of the most valuable ecosystems of the delta could disappear

Cartografía de cobertura del suelo mediante datos de teledetección en la planicie de desborde del río Apure (Venezuela)

La cobertura del suelo es un indicador fundamental para identificar los factores que actúan en el desarrollo de la geomorfología de una planicie aluvial. Esta cobertura se caracteriza por el control que ejerce la vegetación en los procesos hidromorfológicos, así como el mantenimiento y estabilidad de los canales. Se presenta un registro sobre la distribución de cobertura del suelo en el curso medio del sistema anastomosado del río Apure. Se analiza la distribución de los ambientes geomorfológicos en un área de 65 km2 a partir de una combinación de datos de imágenes Landsat-8 y Sentinel-2, integrados en un Sistema de Información Geográfica (SIG). Se estableció una clasificación supervisada mediante los algoritmos Máquinas de Soporte de Vectores y Máxima Verosimilitud. La imagen Landsat fue procesadas a través de una corrección atmosférica, para posteriormente calcular las firmas espectrales. Se encontró seis coberturas: a) sabana arbolada, b) bosque, c) sabana abierta, d) cultivos, e) cuerpos de agua, y f) matorral. No existen diferencias sustanciales en la fiabilidad lograda con los algoritmos de clasificación Máquinas de Soporte de Vectores y Máxima Verosimilitud. Se mostró que la cobertura de sabana arbolada es la de mayor representatividad en el área de estudio con una extensión total de 5.717,26 ha (39%), de las 14.658,77 ha. La clasificación desarrollada presentó una exactitud temática global de 98,08% e índice de Kappa de 0,98. Como resultado se generó una cartografía de cobertura del suelo a partir del mejor clasificador, basándose en el índice Kappa. Estos hallazgos sirven como un referente para aumentar los registros de caracterización de cobertura del suelo, y pueden ser útiles en estudios sobre gestión y uso del territorio, para identificar lugares más susceptibles a la degradación y proponer medidas para el manejo y conservación de los recursos hídricos, que puede ser potencialmente aplicable en ambientes fluviales similares de otras latitudes.

Geomorphological Mapping and Erosion of Abandoned Tailings in the Hiendelaencina Mining District (Spain) from Aerial Imagery and LiDAR Data

The Hiendelaencina district in Spain was the most important silver producer in Europe during 1844–1925. At the end of the 20th century, with mines having closed, some waste rock dumps were reprocessed, and the sludge from the flotation process was stored in two tailings ponds. When this activity ceased, the residues began to be eroded and disperse. In this study, the state of degradation of both deposits was evaluated using historical mapping and light detection and ranging (LiDAR) data, incorporated into a Geographic Information System. In the aerial images (1946–2018), mine tailings and their main erosive and sedimentary forms were mapped. Geoforms linked to hydrological (channels, gullies, alluvial cones), wind (eolian mantles), hydric–gravitational (colluvium) and anthropic (motorbike tracks) processes which move sludge into the surrounding areas were identified. A net loss of 8849 m3 of sludge, a release of 10.3 t of potentially polluting substances and a high erosion rate of 346 t/ha*year were calculated based on LiDAR data from 2009 and 2014. The ponds show a current high degree of erosion that could increase due to both human activity and the growing frequency of drought and torrential rain periods if stabilization measures are not undertaken

Study and Evolution of the Dune Field of La Banya Spit in Ebro Delta (Spain) Using LiDAR Data and GPR

La Banya spit, located at the south of the River Ebro Delta, is a sandy formation, developed by annexation of bars forming successive beach ridges, which are oriented and modeled by the eastern and southern waves. The initial ridges run parallel to the coastline, and above them small dunes developed, the crests of which are oriented by dominant winds, forming foredune ridges and barchans. This study attempted to test a number of techniques in order to understand the dune dynamic on this coastal spit between 2004 and 2012: LiDAR data were used to reconstruct changes to the surface and volume of the barchan dunes and foredunes; ground-penetrating radar was applied to obtain an image of their internal structure, which would help to understand their recent evolution. GPS data taken on the field, together with application of GIS techniques, made possible the combination of results and their comparison. The results showed a different trend between the barchan dunes and the foredunes. While the barchan dunes increased in area and volume between 2004 and 2012, the foredunes lost thickness. This was also reflected in the radargrams: the barchan dunes showed reflectors related to the growth of the foresets while those associated with foredunes presented truncations associated with storm events. However, the global balance of dune occupation for the period 2004-2012 was positive

Quantification of Pollutants in Mining Ponds Using a Combination of LiDAR and Geochemical Methods—Mining District of Hiendelaencina, Guadalajara (Spain)

More than twenty years after the last mining operations were completed in the Hiendelaencina Mining District, it is necessary to carry out a geochemical characterisation of the tailings stored in two contiguous mine ponds. Both have significant amounts of quartz, siderite, barite and muscovite and show significant contents of As, Ba, Pb, Sb and Zn. The tailings show alkaline pH and low electrical conductivity values, which support the visual observation that rules out acid drainage into the environment. The comparison of the National Topographic Map of 1954 with LiDAR data from 2014 has allowed estimating the volume of abandoned waste. Based on the volume of slurry and its average density, the total tonnage of pollutants has been estimated at 279 ± 9 t stored in Pond North and 466 ± 11 t stored in Pond South. Although these are significant quantities that pose a risk to the environment and nearby populations, they are lower than those present in other Spanish districts, such as the Iberian Pyrite Belt or Cartagena-La Unión. The combined use of LiDAR data, aerial imagery and geochemical methods has proven to be very useful for the estimation of the volume of pollutants stored in mine ponds

Main Threats in Mediterranean Coastal Wetlands. The Ebro Delta Case

Coastal wetlands are dynamic ecosystems that exist at the interface between land and sea. They represent environments with a great diversity of habitats and communities, high carbon sequestration capacity and a wide range of ecosystem services. In the Mediterranean, the largest coastal wetlands are found in deltaic areas like that of the Ebro River (Spain), which has a coastline length of approximately 50 km, occupying a total area of 325 km2. The Ebro Delta is included in different national and international frameworks for environmental conservation, despite which there are several risks that threaten it. The lack of sedimentary contributions due to the regulation of the Ebro riverbed (irrigation, reservoirs, and hydroelectric power generation) has caused erosion and the retreat of certain sections of its coastline. To this situation of sediment deficit must be added the threat posed by the effects of global change, such as the rise in sea level, the increase in temperature and in the frequency and intensity of storms. This study analyses the particularities of the coastal wetland of the Ebro Delta, identifying the main threats it faces, as well as possible adaptation and mitigation strategies to these changes

Mapping of landslide susceptibility of coastal cliffs: the Mont-Roig del Camp case study

The weathered and fractured conglomerate cliffs of Mont Roig del Camp constitute a rock fall hazard for the surrounding pocket beaches and, therefore, for the population that frequent them, especially over the summer. Landslide susceptibility of the cliff has been assessed using the Rock Engineering System method (RES). The determinant and triggering factors considered in this study include: wave exposure, shoreline variations, cliff height, cliff slope, geotechnical quality of the rocky mass, superficial runoff and cliff orientations favoring landslides. Geographic Information Systems (GIS) have been employed to facilitate the information analysis and generate new susceptibility maps. The quality of the rock mass and cliff orientation are the most interactive factors for the stability of the cliff. However, shoreline variations and surface runoff are the most dominant factors in the system. Thus, the quality of the rock mass has been determined to be a basic variable in the cliff characterization because of its high dependence on the variations of the remaining factors. The landslide susceptibility map depicts a predominance of surfaces with moderate degrees of susceptibility concentrated mainly in the headlands, where the combined actions of subaerial and marine processes control the weathering and eroding processes. Therefore, the landslide susceptibility assessment based on this methodology has allowed the identification of hazardous areas that should be considered in future management plans

El proyecto EMODnet-Geology: una iniciativa para extender el acceso a los datos geológicos de los océanos y mares europeos

International Symposium on Marine Sciences (6º. 2018. Vigo)Servicio de Cartografía Geológica Marina, Instituto Geológico y Minero de España, EspañaUniversidad Rey Juan Carlos, Españ