Aplicación de modelos de transporte de sedimento en un río permamente con granulometría dispersa

[Resumen] Este trabajo analiza el funcionamiento de diversos modelos de transporte de sedimento en un río permanente con lecho de arena y gravas (Arbúcies, Cordilleras Costero Catalanas). El grado de correlación entre las predicciones de los modelos y las tasas de transporte de sedimento obtenidas en el campo varía considerablemente. El mejor ajuste lo presentan las ecuaciones de ACKERS & WHITE (1973) y ENGELUND & HANSEN (1967), reflejo de su diseño original para ríos de granulometría dispersa y movimiento de dunas en el lecho respectivamente. Los modelos desarrollados por Brownlie (1981) y van Rijn (1984) muestran un funcionamiento más deficiente, a causa del desajuste entre los datos de campo y algunas condiciones de aplicación de los modelos. La discrepancia entre valores estimados y observados pone de relieve la complejidad de los procesos hidráulicos y sedimentológicos en ríos permanentes, relacionados tanto con la migración de formas durante caudales bajos como con la destrucción durante crecidas de sectores del lecho con acorazamiento de gravas.[Abstract] Bed-material load sampled under a wide range of hydraulic conditions in a perennial and poorly sorted sandy gravel-bed river (Arbúcies, Catalan Coastal Ranges), is used to test the performance of four well-know bed-material formulae. The degree of agreement between observed and predicted values varies greatly. The best agreement with measured values was obtained using the ACKERS and WHITE (1973) and ENGELUND & HANSEN (1967) models, a reflection of its original design for poorly sorted sediment and streambed formed into dunes. Contrastingly, the wide range of hydraulic conditions from which the data was obtained and the poor sorting of the bed sediment affected the performance of the van Rijn (1984) and Brownlie (1981) equations and, thus, deserves further study

Assessing controls on the displacement of tracers in gravel-bed rivers

Particle travel length is one of the main dimensions of bedload and strongly influences river morpho-dynamics, particularly when exploring the interactions between sediment transport and channel morphology. This process has been traditionally studied by using tagged stones that allow tracking the movement experienced by individual grains during transport episodes. In this paper, we relate measured particle travel lengths to flow metrics and river channel parameters. First, we link the event-based bedload volumes to the active-layer dimensions, and the product between the average bedload rates and the duration of competent flows. We then hypothesize that travel length depends on channel width, surface grain-size, particle size, bed structure, flow strength, and duration of competent flow. The results from this approach are, subsequently, tested with a set of tracer observations from eight rivers that were available in the literature. The relationship between travel length and flow metrics was found to be statistically strong and has the potential to allow us to quantitatively assess the one-day dynamics of particles moving along streambeds. We also analyzed the influence of channel morphology and bed structure and identified morphological signatures for particle transport in gravel-bed rivers.The present work has been possible thanks to the financial support provided by the grant ACB17-44, co-funded by the post-doctoral ‘Clarín’ program-FICYT (Government of the Principality of Asturias) and the Marie Curie Co-Fund. This research was partly undertaken through the MorphPeak (CGL2016-78874-R) project funded by the Spanish Ministry of Economy and Competiveness and the European Regional Development Fund Scheme. Authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through the Consolidated Research Group ‘Fluvial Dynamics Research Group’ -RIUS (2017 SGR 459), as well as support from the project RIVERCHANGES-CGL2015-68824-R (MINECO/FEDER, UE)

Post-eruption morphological evolution and vegetation dynamics of the Blanco River, southern Chile

In this study, we analysed the morphological evolution of a channel segment in the Blanco River in southern Chile that was affected by the Chaitén Volcano eruption occurred in 2008–2009. Through a series of high-resolution satellite images from 2005 to 2019 that represents the entire pre- and post-eruptive dynamics and land covers, we tracked the geomorphological evolution of a 5.65-km-long river segment using channel form indices and also monitored the vegetation dynamics using object-based image analysis (OBIA). Discharge record for the Blanco River was also reconstructed to support the analysis of channel morphologic process. The study aims at examining whether a) the river channel is still adjusting 10 years after the eruption and if so, at what magnitude and, b) the recovered riparian vegetation plays a significant role in stabilising the river streambanks and terraces. We found that even 10 years after the eruption, the Blanco River channel planform is still adjusting, showing a simpler and stable channel configuration in the upstream reaches of the valley, where a certain degree of equilibrium appears to have been attained. More dynamic morphologies were observed in the reaches downstream that have to accommodate the arrival of large amounts of freshly eroded sediments. Our analysis showed that the occurrence of competent floods capable of reworking the river channel matches with the geomorphic indices and mark the post-eruption adjustments of the channel. Finally, the in-channel and riparian vegetation does not play a significant role in stabilising the active channel, streambanks, and terraces, reinforcing the recolonization of sedimentary active areas occurring elsewhere in the valley.This research was developed within the frame of the project FONDECYT 1170413 funded by the Chilean Government. Authors acknowledge the support of the Economy and Knowledge Department of the Catalan Government through the Fluvial Dynamics Research Group (RIUS) SGR017-459

Application of Structure-from-Motion photogrammetry to river restoration

This research is funded by the Environment Agency and United Utilities whose support is gratefully acknowledged. Some of the methods employed in this work have been tested on the background of the results obtained in MorphSed (www.morphsed.es), a research project funded by the Spanish Ministry of Economy and Competiveness and the European Regional Development Fund Scheme (FEDER; CGL2012-36394). The second author is funded by a Ramon y Cajal Fellowship (RYC-2010-06264). Authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through the Consolidated Research Group ‘Fluvial Dynamics Research Group’ (2014 SGR 645). The authors thank Manel Llena from the University of Lleida for his help and contribution to the camera calibration experiments. We are also grateful to the three anonymous reviewers and the editors for their comments that greatly improved the manuscript.Peer reviewedPostprin

Efectos de un incendio forestal sobre la respuesta hidrológica de la cuenca mediterránea de Arbúcies (cordilleras costeras catalanas, NE España)

We analyse the hydrological response of the Arbúcies River basin after a wildland fire occurred in August 1994, which burnt 15% of its drainage area. The Arbúcies River is located in the Catalan Coastal Ranges, draining an area of 106 km2. Deep sandy soils are predominant in the catchment. The study is based on rainfall and runoff records (1991-1997), from which twenty-six flood events were selected. River response, especially runoff volume and peak discharge, showed a remarkable increment for events occurred six months after the fire, in comparison with those of similar magnitude prior the fire. The higher the magnitude of the episodes the higher the degree of hydrological alteration. Maximum increment of peak discharge is 173%, which is susbtantially more important that that produced on the effective rainfall (+40%). Flood events tend to recover pre-fire hydrological response eighteen months after the fire.En agosto de 1994 un incendio forestal afectó al 15% de la superficie de la cuenca experimental de la riera de Arbúcies. Se trata de una cuenca mediterránea de 106 km2, en la que predominan las masas de frondosas y los suelos arenosos y profundos. A partir de los registros continuos de precipitación y caudal, anteriores y posteriores al incendio (1991-1997), se seleccionaron 26 episodios con el objetivo de detectar modificaciones en la respuesta hidrológica de la cuenca debidas a los efectos del fuego. Se ha detectado una mayor respuesta hidrológica para los episodios hasta seis meses después del incendio, tanto en volumen de escorrentía como en caudal máximo, siendo más acusado el incremento para los episodios de mayor magnitud. El incremento estimado en el caudal punta para el valor máximo del rango de registros de precipitación total es del 173%, mayor que el producido en la estimación de la precipitación neta, que es solamente del 40%. Los eventos ocurridos a partir de un año y medio después del incendio muestran una tendencia a la recuperación de la respuesta hidrológica previa al incendio

Orbitofrontal and caudate volumes in cannabis users: a multi-site mega-analysis comparing dependent versus non-dependent users.

Cannabis (CB) use and dependence are associated with regionally specific alterations to brain circuitry and substantial psychosocial impairment.The objective of this study was to investigate the association between CB use and dependence, and the volumes of brain regions critically involved in goal-directed learning and behaviour-the orbitofrontal cortex (OFC) and caudate.In the largest multi-site structural imaging study of CB users vs healthy controls (HC), 140 CB users and 121 HC were recruited from four research sites. Group differences in OFC and caudate volumes were investigated between HC and CB users and between 70 dependent (CB-dep) and 50 non-dependent (CB-nondep) users. The relationship between quantity of CB use and age of onset of use and caudate and OFC volumes was explored.CB users (consisting of CB-dep and CB-nondep) did not significantly differ from HC in OFC or caudate volume. CB-dep compared to CB-nondep users exhibited significantly smaller volume in the medial and the lateral OFC. Lateral OFC volume was particularly smaller in CB-dep females, and reduced volume in the CB-dep group was associated with higher monthly cannabis dosage.Smaller medial OFC volume may be driven by CB dependence-related mechanisms, while smaller lateral OFC volume may be due to ongoing exposure to cannabinoid compounds. The results highlight a distinction between cannabis use and dependence and warrant examination of gender-specific effects in studies of CB dependence