Person:
Ortega Becerril, José Antonio

First Name

José Antonio

Last Name

Ortega Becerril

URI

https://hdl.handle.net/20.500.14352/83675

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Area

Geodinámica Externa

Identifiers

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Now showing 1 - 10 of 14

Relación entre periodos frios y cambios de patrón de macroescala (Oscilación del Atlántico Norte) en las inundaciones en el Río Guadiana
(Geogaceta, 2007) Ortega Becerril, José Antonio; Garzón Heydt, Guillermina
Global changes in climate have been widely documented but the relationships between these changes and floods are not easy to establish. Hydroclimatology offers an important tool in order to improve our knowledge about the flood producing mechanisms, which can be used to explain historical and palaeohydrological events. Storm cells and mesoscale systems develop into small floods, mainly at tributary streams. But a synoptic scale relates better to Guadiana River floods, dominant in winter. At a higher level, macroscale atmospheric configuration can also explain flood generation at the Guadiana River and, particularly, the North Atlantic Oscillation (NAO) that is one of the most important recurrent patterns of atmospheric circulation. There is no reliable evidence, however relating NAO and historical floods in Europe, especially for central European countries. This situation changes in the Iberian Peninsula, specially in the Southwest that shows a good relationship between winter floods and a negative NAO phase. Recent Guadiana River floods (XX century) could be related to these phenomena, but there´s not and index who covers previous events. Guadiana palaeoflood records compiled using slackwater deposits are dated by 14C radiometric methods and associated, when it is possible to a historical flood event. Results shows event clusters during cooling phases and it is likely that they reflect moments of climatic variability.
Factors affecting the performance of P22 ELISA for the diagnosis of caprine tuberculosis in milk samples
(Research in Veterinary Science, 2022) Ortega Becerril, José Antonio; Infantes Lorenzo, José Antonio; Roy, A.; Juan Ferré, Lucía De; Romero Martínez, Beatriz; Moreno, I.; Domínguez, M.; Bezos Garrido, Javier; Domínguez Rodríguez, Lucas José
Caprine tuberculosis (TB) is a zoonosis caused by members of the Mycobacterium tuberculosis complex (MTBC). Caprine TB eradication programmes are based mainly on intradermal tuberculin tests and slaughterhouse surveillance. However, the use of serological test has been extended as a potential diagnostic tool in goats through the use of serum, plasma, or even milk samples. Milk production and the antibodies (Ab) present in milk can vary depending on several circumstances. In the present study, different factors that may affect the performance of humoral TB diagnosis were analysed using goat milk samples: 1) lactation stage, 2) a recent previous skin test (booster effect) and 3) the effect of freeze-thaw cycles on milk samples preserved with azidiol. TB-infected animals (n = 44) were selected to evaluate the evolution of the Ab levels during the 6-month lactation period, along with its potential effect on the P22 ELISA results. In general, no significant changes (p = 0.079) were observed throughout the study as regards Ab levels in milk samples between consecutive analysis although the reactivity to P22 ELISA decreased when samplings were performed at the last two months of the lactation. Regarding the booster effect, the quantitative results showed a significant variation (p < 0.001) for both milk and serum samples when serological tests were carried out 15 days after the skin test. Finally, there were no significant differences (p = 0.99) in the P22 ELISA results when using milk samples preserved with azidiol that had undergone freeze-thaw cycles.
El estudio de la morfología de los ríos en roca. Implicaciones hidrogeológicas y evolutivas en dos barrancos españoles.
(Boletín geológico y minero, 2007) Ortega Becerril, José Antonio
España es un país con una enorme riqueza en sistemas fluviales y torrenciales, sobre todo de montaña. Los ríos desarrollados sobre roca resistente (ríos en roca) encierran muchas respuestas aplicables a los interrogantes de los ríos aluviales. La baja tasa de erosión y su buena preservación hacen de ellos unos excelentes laboratorios naturales. Su morfología general y las formas menores aparecen como respuesta a condiciones locales como la pendiente y los aportes líquidos y sólidos. El sustrato juega un papel importante, pero no fundamental, en el desarrollo de la morfología. Es el régimen de caudales el más importante de los factores que condicionan las formas, y las crecidas y avenidas el instrumento del que se vale para realizar los cambios a nivel puntual. El equilibrio no se alcanza a escala de cuenca o de río al completo, más bien parece obedecer a tramos de tamaño pequeño o inclusive a nivel puntual. Podemos entender un río en roca como un sistema con múltiples niveles de base (sistemas de poza y escalón) en el que la hidráulica y el clima, las lluvias fundamentalmente, condicionan la forma final y en el que la degradación o erosión se produce a lo largo de múltiples tramos y no de forma unidireccional aguas arriba (erosión remontante). En los dos ejemplos estudiados aparecen a lo largo de un tramo de pocos kilómetros, zonas con morfología y funcionamiento distintas y que no obedecen a una gradación normal en la evolución o madurez fluvial.
Morphometric measurements of bedrock rivers at different spatial scales and applications to geomorphological heritage research
(Progress in Earth and Planetary Science, 2019) Gómez Heras, Miguel; Ortega Becerril, José Antonio; Garrote Revilla, Julio; Fort González, Rafael; López González, Laura
Morphometric characterisation is particularly relevant in the study of geomorphological heritage. 3D modelling techniques have been proven as very useful tools to recognise, characterise and valorise geomorphosites. Bedrock rivers account for one of the most outstanding aspects within geomorphological heritage due to the amount of distinctive and attractive geomorphological features associated to them and the high preservation of sculpted forms. Digital elevation models (DEMs) have made it increasingly possible to establish accurate morphometric indices and establish clearer connections between forms and processes. This paper reviews different methodologies to obtain DEMs on bedrock rivers. This review goes from DEM analysis at multiple spatial scales to introduce optical microrugosimeter as the latest technical development to facilitate micromorphometric analysis. Micromorphometric analysis opens the scope for improving the knowledge we have on trans-scale issues in bedrock rivers. Micromorphometric analysis also opens a new layer of information that enriches the public’s valuation of geodiversity of geomorphosites by increasing its didactic and interpretative potential.
Paleocrecidas, avenidas recientes e hidroclimatología en la cuenca media y baja del río Guadiana
(2008) Ortega Becerril, José Antonio; Garzón Heydt, Guillermina
Las inundaciones en la Cuenca del río Guadiana están relacionadas con múltiples elementos: cambios en los usos del suelo, modificaciones antrópicas, parámetros climáticos y meteorológicos y cambios en dichos parámetros. Existen diferencias en las inundaciones, encontrándose poblaciones referidas a distintas situaciones hidrometeorológicas, e incluso con cambios en los patrones climáticos y su escala. Ésta es una de las características del clima que afectan más a los mecanismos de producción de crecidas. Las paleoinundaciones son una potente herramienta para profundizar en el estudio de las avenidas y comprender su evolución actual. Se han encontrado grupos de avenidas antiguas que alcanzan los 3260BP años, y que al datarse mediante radioisótopos nos han permitido encontrar asociaciones con el momento climático, fundamentalmente pulsaciones frías en el clima. Las avenidas recientes, como la del río Rivillas en 1997, suponen una gran ocasión para comprender los mecanismos de crecida de una flashflood y los cambios geomorfológicos que ocasionan en una cuenca de pequeño tamaño, como la del Rivillas. Los elementos morfosedimentarios encontrados y su relación con los parámetros y variables de la crecida permiten ahondar en un campo por estudiado por lo efímero de los depósitos de crecida. Se han testado asimismo los distintos métodos de cálculo del caudal máximo de la crecida, permitiendo comprobar la validez del método geomorfológico combinado con el hidráulico.
Recent human impacts and change in dynamics and morphology of ephemeral rivers
(Natural Hazards and Earth System Sciences, 2014) Ortega Becerril, José Antonio; Razola, Laura; Garzón Heydt, Guillermina
Ephemeral streams induce flash-flood events, which cause dramatic morphological changes and impacts on population, mainly because they are intermittent and less predictable. Human pressures on the basin modify load and discharge relationships, inducing dormant instability on the fluvial system that will manifest abruptly during flood events. The flash-flood response of two ephemeral streams affected by load supply modification due to land use changes is discussed in a combination of geomorphic and hydraulic approaches. During the Rivillas flash flood, intensive clearing on the basin led to high rates of sediment flowing into an artificially straightened and inefficient channel. The stream evolved from a sinuous single channel into a shallow braiding occupying the entire width of the valley floor. Misfits and unsteady channel conditions increased velocity, stream power and sediment entrainment capacity and considerably magnified flood damage. Resulting morphosedimentary features revealed a close relationship with the valley floor postflood hydraulic model, and pre-event awareness would have made it possible to predict risk-sensitive areas. In the second case, the Azohía stream, modelling of current pre-flood channel conditions make it possible to determine channel narrowing and entrenchment in the lower alluvial fan stretch. Abandonment of intensive agriculture, basin reforestation and urbanization diminish load contribution and trigger channel incision. This induces an increase in slope and velocity in the bankfull channel, producing renewed erosive energy and thus activating upstream propagation of incision and bank undermining. The absence of water-spreading dynamics on the alluvial fan in favour of confinement in a single channel produces an unstable dynamic in the system, also offering a false sense of stability, as long as no large magnitude floods occur. When modelling flood-prone areas and analysing hydraulic variables, it is important to detect possible anthropic disturbances that may affect basin load budgets in order to anticipate catastrophic consequences resulting from inappropriate fluvial management before the occurrence of an extraordinary event.
Magnitude of formative flows in stream potholes
(Geomorphology, 2023) Ortega Becerril, José Antonio; Garrote Revilla, Julio
Although it is generally recognized that geomorphic work is tied to bedrock channel reshaping, the importance of low vs. high flow stages that cause the most geomorphic impact remains unclear. The objective of the research is to study the concept of “formative flow” in bedrock channels and determine, through morphological studies, if those flows have any impact on sculpted features such as potholes and how this relationship relates to various inputs such as flow stages (magnitude and frequency), shear stress, and sediment size. Here, we studied the distribution of the main pothole typologies and tried to understand why potholes are found along bedrock river channels. Specifically, we examined stream potholes from three locations along the Spanish Central System: Alberche, Tietar, and Manzanares rivers. We conducted the research by taking precise geometric measurements, classifying potholes, analyzing flow magnitude and frequency, and using a two-dimensional (2D) hydrodynamic model to assess key variables in Manzanares river. This research demonstrated that bankfull depths completely cover all pothole typologies in all the analyzed sites but are not sufficient to achieve its formative flow depth (FFD). Using a detailed 2D hydrodynamic model in Manzanares river, we discovered that dimensions of cylindrical potholes are closely related to bankfull discharge and that this depth is connected to FFD. Other potholes, such as erosive-compound and erosive-lateral, are historical remnants, and their shapes are not related to any particular FFD and are likely associated with rare events and catastrophic breaks. A collection of laterals that exhibit FFD near bankfull flows appear to represent a part of the recent evolution of a knickpoint. To summarize, it can be inferred from the findings that the utility of morphological analysis in conjunction with the 2D hydrodynamic model is to examine the fraction of erosional/active features to determine the degree of senescence and/or change in natural conditions in a river reach.
Wildfire-Induced Changes in Flood Risk in Recreational Canyoning Areas: Lessons from the 2017 Jerte Canyons Disaster
(Water, 2022) Ortega Becerril, José Antonio; Garrote Revilla, Julio; Vicente, Álvaro; Marqués, María José
Few studies identify potential hazards affecting canyoning. This activity has an increasing number of practitioners, and hence, a greater number of people are affected by potential natural hazards. Mountain rivers are located in places subject to several hydrological hazards; the risks are mostly connected with floods produced by intense storms or dam operation, but changes in hydrological factors may alter the usual basin behavior given even moderate or less severe storms. Data about flood events and the peak discharge of the 2017 flood in the two studied canyons were collected by means of a quick field survey of water levels after the flood, hydrological modeling, and soil analysis. The present research shows the dramatic consequences of a two-year return period storm affecting a guided group of canyoneers. A previous wildfire changed the soil, leading to hydrophobic conditions and increasing the flood effects. Peak discharge increased from 2 m3 s−1 in normal conditions to 12 m3 s−1 under a hydrophobic regime related to wildfire occurrence; moreover, a reduction in the time of concentration also occurred, pointing to a more powerful and dangerous flood event. In this paper, some hydrological recommendations are highlighted that will be helpful in recreational canyoning management, leading to safer practice.
A contribution to improved flood magnitude estimation in base of palaeoflood record and climatic implications – Guadiana River (Iberian Peninsula)
(Natural Hazards and Earth System Sciences, 2009) Ortega Becerril, José Antonio; Garzón Heydt, Guillermina
The Guadiana River has a significant record of historical floods, but the systematic data record is only 59 years. From layers left by ancient floods we know about we can add new data to the record, and we can estimate maximum discharges of other floods only known by the moment of occurrence and by the damages caused. A hydraulic model has been performed in the area of Pulo de Lobo and calibrated by means of the rating curve of Pulo do Lobo Station. The palaeofloods have been dated by means of 14C y 137Cs. As non-systematic information has been used in order to calculate distribution functions, the quantiles have changed with respect to the same function when using systematic information. The results show a variation in the curves that can be blamed on the human transformations responsible for changing the hydrologic conditions as well as on the latest climate changes. High magnitude floods are related to cold periods, especially at transitional moments of change from cold to warm periods. This tendency has changed from the last medium-high magnitude flood, which took place in a systematic period. Both reasons seem to justify a change in the frequency curves indicating a recent decrease in the return period of big floods over 8000m3 s−1. The palaeofloods indicate a bigger return period for the same water level discharge thus showing the river basin reference values in its natural condition previous to the transformation of the basin caused by anthropic action.
Controls on strath terrace formation and evolution: The lower Guadiana River, Pulo do Lobo, Portugal
(Geomorphology, 2018) Ortega Becerril, José Antonio; Garzón Heydt, Guillermina; Tejero López, Rosa
The lower Guadiana River carves a wide canyon in the Variscan metamorphic rocks of the SW Iberian Peninsula and presents an exceptionally homogeneous and well-preserved case of a strath terrace (ST) some 40 km long and 400 m wide. The rocky surface or strath shows different characteristics and development stages. Upstream, the lateral erosion level forms a flooded riverbed, or submerged strath, that gradually rises above the thalweg and develops into an active floodplain. Downstream, below the 15 m high Pulo do Lobo waterfall, the strath is incised by an inner canyon that forms a terrace on both sides. The inner channel increasingly widens and the ST loses its longitudinal continuity, yet remains prone to flooding during extraordinary magnitude floods. To assess the factors controlling the formation of this ST, we examined the roles of key drivers of ST formation: lithological hardness, tectonic structures and climate change, using cosmogenic data to create a chronologic context. The ST developed favoured by a monotonous succession of phyllites, as shown by Schmidt hammer resistance data, and interbedded more resistant quartz veins do not significantly alter its flat configuration. Variscan structures and measured joints determine the main orientation of the river and control the drainage network pattern. The intersection of the NS and NE-SW fractures promotes a wavy surface due to three-dimensional minor fold trains that act as discontinuities and play an important role in ST erosion through quarrying and plucking. However, we detected no evidence of ST deformation attributable to recent or Late Cenozoic tectonic activity. The upstream active riverbed progressively changes downstream into an ST. This implies that Be radiometric ages obtained at Pulo do Lobo may not represent the ST's genetic age but rather the time of dismantling of its alluvial or sedimentary cover. This means the strath surface formed prior to its cosmogenic age and was therefore controlled by a higher base level, indicating a higher sea level than the current one, given the downstream area studied. The Quaternary sea level fluctuations show records of only a few meters above the current level. Instead, the sea level low stand maintains an average depth of −60 m, reaching −140 m during the last glacial period. This low base level context could justify the strong incision of the inner channel within the ST, but not the age of strath surface genesis and expansion and thus this surface should have evolved previously. The highest possible sea level stand corresponds to the Pliocene transgression, which reached an elevation of 120 m in the region, covering Miocene paleorelief. The mouth of the Guadiana River at that time resembled a fluvio-deltaic embayment between the Algarve domain and the Guadalquivir depression, which was infilled with fluvial deposits at the end of the transgression. Collectively, these data suggest that cosmogenic dating would define the time of exhumation of this Pliocene sedimentary cover. Despite great variation of the ST ages, estimated incision rates at the knickpoint area are consistent with the total entrenchment of the Pulo do Lobo fall, especially if we consider that data correspond to an active erosion site. Highest erosion rates were found for the pothole area compared to those obtained for the higher ST surface. Radiometric ages correspond to the period of lowest Quaternary sea level and during which headward erosion would have been very active in the inner channel. The waterfall area shows more resistant lithology in its concentrated quartz veins, but this effect is inconspicuous at the ST surface. The regular gradient of 0.02 m/m and vast extension of this perched strath, linked upstream to the Guadiana riverbed, indicates a relic exhumed surface beneath its sedimentary cover. Notwithstanding the subsiding activity of the Gulf of Cádiz, the continental margin behaves as a tectonically stable block, which allows for the persistence of former morphologies in these ancient landscapes reshaped by bedrock river dissection.