Análisis y modelización de la contribución de la erosión por cárcavas a la producción de sedimentos en la cuenca del Guadalquivir

Gully erosion is widely recognised as an important soil degradation process in many regions, causing important on-site (e.g. soil losses, environmental degradation, crop losses...) and off-site effects (e.g. muddy floods, water pollution, reservoir siltation...). In contrast to other erosion processes, as for instance sheet and rill erosion, where models have been successfully developed and tested extensively over the world, no widely accepted model exists for gully erosion. The reasons for this are the varied and complex subprocesses involved in gully erosion, the factors that control it and, its dependence on the spatial and temporal scale of study. Notwithstanding the above, gully erosion has been proved to be the major erosion process contributing to the total sediment yield in various regions, especially in the Mediterranean Region. This is particularly the case of the Guadalquivir River Basin, where the lithology added to the topography and the climate condition make of it a gully prone area. At present, very little information is available on gully processes and dynamics in this area. In this thesis, a complex gully network with a contributing area of 20 km2 was selected as a representative case of the gully prone agricultural landscape of the Campiña of the Guadalquivir River Basin, which land use consists mainly of herbaceous crops and live groves on Vertisols developed over soft parent material (marls and calcareous sandstone). The dynamics of the gully network was study over a period of 57 years by a combination of photointerpretation techniques in a GIS, field surveys and probabilistic approaches. Gully network evolution was derived from a dataset of 10 aerial orthophotos from the period 1956 to 2013. Field data and a Monte Carlo approach were then applied to estimate gully erosion rates dynamics over the study period. Modelling of gully erosion was then assessed by means of the study of the topographic thresholds for gully head initiation and by means of the gully widening rates dynamics. The results showed that gully erosion rate in the study area was 39 ton/ha/year on average, with peaks up to 591 ton/ha/year. However, these gully erosion rates were highly variable over the study period, and therefore the estimation through average values should be taking with caution. The variability on the gully erosion rates obtained highlights the importance of appropriately selecting the time scale on which gully erosion processes are assessed. For the first time, an important temporal variability in the topographic thresholds (TT) values for a given study area was demonstrated. In addition, this TT variability could be correlated to rainfall regime through various rainfall indexes, as for instance the Rainy Day Normal (RDN). A significant correlation between the gully widening rates and the runoff contributing area were found. Variability in gully widening rates were related to a rainfall index expressing the number of days exceeding a threshold rainfall depth of 13 mm. Land use present in the study area (herbaceous crops and olive groves) showed no significant effects on the TT and the widening rates.La erosión por cárcavas es un proceso de degradación del suelo que afecta gravemente a muchas regiones. Estos procesos causan importantes impactos tanto in-situ como ex-situ. A diferencia de lo que ocurre con otros procesos de erosión, como son la erosión laminar y la erosión por regueros, para la erosión por cárcavas no hay desarrollados en la actualidad modelos ampliamente aceptados. Sin embargo, distintos autores han demostrado que la contribución de las cárcavas a la producción total de sedimentos puede superar con creces la del resto de procesos en determinadas regiones, como ocurre por ejemplo en la cuenca del Mediterráneo. En esta tesis se ha analizado una cuenca de la Campiña representativa de las zonas más afectadas por la erosión por cárcavas en la Cuenca del Río Guadalquivir. Mediante técnicas de fotointerpretación de imágenes aéreas, se analizó la dinámica de la red de cárcavas en un periodo de 57 años. Para ello se utilizó una secuencia de 10 ortofotos del periodo comprendido entre 1956 y 2013, con el apoyo de datos de campo. Por último, se avanzó en la modelización de las cabeceras de las cárcavas y del ensanchamiento de las mismas a través de relaciones con el área de contribución, y con índices de precipitación. Los resultados obtenidos mostraron que las tasas de erosión durante el periodo de estudio fueron muy variables, siendo de 39 t ha-1 año-1 el valor medio para el conjunto del periodo y 591 t ha-1 año-1 el máximo obtenido. Por otro lado, se demostró que los umbrales topográficos para la formación de cabeceras pueden variar notablemente a lo largo del tiempo en un mismo área. Por último, se determinó que existe una correlación significativa entre la tasa de ensanchamiento de las cárcavas y el área de contribución aguas arriba. Tanto los umbrales topográficos como las tasas de ensanchamiento pudieron correlacionarse con índices de precipitación. Mientras que, los distintos usos del suelo presentes en la zona de estudio, resultaron poco relevantes para la modelización de los crecimientos en cabecera y en anchura

Studying the influence of livestock pressure on gully erosion in rangelands of SW Spain by means of the UAV+SfM workflow

Gully erosion in agrosilvopastoral systems of SW Spain represents a common degradation process, but has been hardly analysed. The suitability of using the Unmanned Aerial Vehicles (UAV) and Structure from Motion photogrammetry (SfM) workflow to map small valley-bottom gullies in these landscapes was tested. The results showed centimetre-level accuracy. Observed strengths and limitations of the UAV+SfM workflow in the study areas are discussed. The resulting cartography allowed mapping soil erosion forms at outstanding spatial scales. All study areas showed evidences of degradation

Climate Aridity and the Geographical Shift of Olive Trees in a Mediterranean Northern Region

[EN] Climate change leverages landscape transformations and exerts variable pressure on natural environments and rural systems. Earlier studies outlined how Mediterranean Europe has become a global hotspot of climate warming and land use change. The present work assumes the olive tree, a typical Mediterranean crop, as a candidate bioclimatic indicator, delineating the latent impact of climate aridity on traditional cropping systems at the northern range of the biogeographical distribution of the olive tree. Since the olive tree follows a well-defined latitude gradient with a progressive decline in both frequency and density moving toward the north, we considered Italy as an appropriate case to investigate how climate change may (directly or indirectly) influence the spatial distribution of this crop. By adopting an exploratory approach grounded in the quali-quantitative analysis of official statistics, the present study investigates long-term changes over time in the spatial distribution of the olive tree surface area in Northern Italy, a region traditionally considered outside the ecological range of the species because of unsuitable climate conditions. Olive tree cultivated areas increased in Northern Italy, especially in flat districts and upland areas, while they decreased in Central and Southern Italy under optimal climate conditions, mostly because of land abandonment. The most intense expansion of the olive tree surface area in Italy was observed in the northern region between 1992 and 2000 and corresponded with the intensification of winter droughts during the late 1980s and the early 1990s and local warming since the mid-1980s. Assuming the intrinsic role of farmers in the expansion of the olive tree into the suboptimal land of Northern Italy, the empirical results of our study suggest how climate aridity and local warming may underlie the shift toward the north in the geographical range of the olive tree in the Mediterranean Basin. We finally discussed the implications of the olive range shift as a part of a possible landscape scenario for a more arid future.Rodrigo-Comino, J.; Salvia, R.; Quaranta, G.; Cudlín, P.; Salvati, L.; Giménez Morera, A. (2021). Climate Aridity and the Geographical Shift of Olive Trees in a Mediterranean Northern Region. Climate. 9(4):1-18. https://doi.org/10.3390/cli9040064S1189

Geomorphometry 2020. Conference Proceedings

Geomorphometry is the science of quantitative land surface analysis. It gathers various mathematical, statistical and image processing techniques to quantify morphological, hydrological, ecological and other aspects of a land surface. Common synonyms for geomorphometry are geomorphological analysis, terrain morphometry or terrain analysis and land surface analysis. The typical input to geomorphometric analysis is a square-grid representation of the land surface: a digital elevation (or land surface) model. The first Geomorphometry conference dates back to 2009 and it took place in Zürich, Switzerland. Subsequent events were in Redlands (California), Nánjīng (China), Poznan (Poland) and Boulder (Colorado), at about two years intervals. The International Society for Geomorphometry (ISG) and the Organizing Committee scheduled the sixth Geomorphometry conference in Perugia, Italy, June 2020. Worldwide safety measures dictated the event could not be held in presence, and we excluded the possibility to hold the conference remotely. Thus, we postponed the event by one year - it will be organized in June 2021, in Perugia, hosted by the Research Institute for Geo-Hydrological Protection of the Italian National Research Council (CNR IRPI) and the Department of Physics and Geology of the University of Perugia. One of the reasons why we postponed the conference, instead of canceling, was the encouraging number of submitted abstracts. Abstracts are actually short papers consisting of four pages, including figures and references, and they were peer-reviewed by the Scientific Committee of the conference. This book is a collection of the contributions revised by the authors after peer review. We grouped them in seven classes, as follows: • Data and methods (13 abstracts) • Geoheritage (6 abstracts) • Glacial processes (4 abstracts) • LIDAR and high resolution data (8 abstracts) • Morphotectonics (8 abstracts) • Natural hazards (12 abstracts) • Soil erosion and fluvial processes (16 abstracts) The 67 abstracts represent 80% of the initial contributions. The remaining ones were either not accepted after peer review or withdrawn by their Authors. Most of the contributions contain original material, and an extended version of a subset of them will be included in a special issue of a regular journal publication

Detecting soil erosion in semi-arid Mediterranean environments using simulated EnMAP data

Soil is an essential nature resource. Management of this resource is vital for sustainability and the continued functioning of earths atmospheric, hydrospheric and lithospheric functioning. The assessment and continued monitoring of surface soil state provides the information required to effectively manage this resource. This research used a simulated Environmental Mapping and Analysis Program (EnMAP) hyperspectral image cube of an agricultural region in semi- arid Mediterranean Spain to classify soil erosion states. Multiple Endmember Spectral Mixture Analysis (MESMA) was used to derive within pixel fractions of eroded and accumulated soils. A Classification of the soil erosion states using the scene fraction outputs and digital terrain information. The information products generated in this research provided an optimistic outlook for the applicability of the future EnMAP sensor for soil erosion investigations in semi-arid Mediterranean environments. Additionally, this research verifies that the launch of the EnMAP satellite sensor in 2018 will provide the opportunity to further improve the monitoring of earth finite soil resources.NSERC create AMETHYST , Alberta Terrestrial Imaging Centre

Measuring, modelling and managing gully erosion at large scales: A state of the art

Soil erosion is generally recognized as the dominant process of land degradation. The formation and expansion of gullies is often a highly significant process of soil erosion. However, our ability to assess and simulate gully erosion and its impacts remains very limited. This is especially so at regional to continental scales. As a result, gullying is often overlooked in policies and land and catchment management strategies. Nevertheless, significant progress has been made over the past decades. Based on a review of >590 scientific articles and policy documents, we provide a state-of-the-art on our ability to monitor, model and manage gully erosion at regional to continental scales. In this review we discuss the relevance and need of assessing gully erosion at regional to continental scales (Section 1); current methods to monitor gully erosion as well as pitfalls and opportunities to apply them at larger scales (section 2); field-based gully erosion research conducted in Europe and European Russia (section 3); model approaches to simulate gully erosion and its contribution to catchment sediment yields at large scales (section 4); data products that can be used for such simulations (section 5); and currently existing policy tools and needs to address the problem of gully erosion (section 6). Section 7 formulates a series of recommendations for further research and policy development, based on this review. While several of these sections have a strong focus on Europe, most of our findings and recommendations are of global significance.info:eu-repo/semantics/publishedVersio

UAVs for the Environmental Sciences

This book gives an overview of the usage of UAVs in environmental sciences covering technical basics, data acquisition with different sensors, data processing schemes and illustrating various examples of application