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- Effects of tidal and river discharge forcings on tidal propagation along the Guadiana EstuaryPublication . Calero Quesada, Maria Concepcion; Garcia-Lafuente, Jesus; Garel, Erwan; Delgado Cabello, Javier; Martins, Flávio; Moreno-Navas, JuanA numerical model is implemented to explore the effect of the river discharge on tidal propagation along the Guadiana Estuary, a rock-bound estuary located in Southwest Iberia. The MOHID numerical model, in 2D barotropic mode, has been forced by tides at the ocean side and by freshwater at the upstream boundary of the domain. The model was validated using water level and velocity observations at several locations along the estuary. Different scenarios with variable tidal forcings and freshwater discharges were analysed, considering the semi- diurnal constituents and M4 overtide, in order to assess the influence of each external agent on the along-channel hydrodynamics. The model reproduces the expected general tidal properties along the channel in terms of amplitude (of both elevation and current), asymmetry and phase between horizontal and vertical tides. Three zones along the estuary have been defined based on the overtide patterns. Tidal propagation in Zone I, at the lower estuary, vary essentially with the tidal amplitude at the mouth while changes due to river discharge are minor. Along Zone II (middle estuary), the tidal forcing still predominates, for low discharge values only. Along Zone III (upper estuary), the tidal propagation is primarily controlled by the river discharge. Although the discharge threshold vary with the location and parameter considered, it is estimated that a discharge as little as 100 m3/s has a strong effect on the tidal properties along the system as a whole. It is therefore concluded that tidal properties in rock-bound estuaries may be importantly modified by relatively weak river discharge events.
- Improving the response to operational pollution in the South Iberian coast A Super-Ensemble backtracking approachPublication . Janeiro, João; Sepp Neves, Antonio Augusto; Martins, Flávio; Campuzano, FranciscoAlthough for the general public marine oil pollution happens when an oil tanker sinks in the ocean or an accident occurs in an oil platform, most of the oil entering the world ocean does it along less obvious paths. This research work focus on operational spills. It provides a first indication of the uncertainty associated to backtracking simulations using solutions from several operational models available on the internet for the South Iberia region. The suitability of using a Super-Ensemble approach as a way of minimizing the uncertainty was also investigated. The methodology was validated using drifting buoys available for the region. Results show the advantages of using the Super-Ensemble while pointing out for the importance of the atmospheric forcing in this region due to its characteristic mesoscale activity. The absence of more trajectories sparse in time and geographic coverage was a limitation found.
- Influence of the Barrie de la Maza dock on the circulation pattern of the Ria of A Coruna (NW-Spain)Publication . Gomez-Gesteira, M; Decastro, M; Prego, R; Martins, FlávioA 3D hydrodynamical model is applied to the ria of A Coruna to analyze the evolution of the circulation pattern in the ria after the building of a breakwater (Barrie de la Maza dock) in the sixties. This circulation pattern has changed greatly. On the one hand, the circulation, which was almost parallel to the shore line under the original conditions, now shows a gyre near the end of the dock. On the other hand, a considerable increase (about 30%) in the velocities near the end of the breakwater and in the main channel of the estuary has been observed after the building of the dock. A stronger bottom shear stress has been generated in the estuary areas where the velocity increased. The bottom shear stress increase was particularly great (over 100%) near the end of the dock. This increase in the shear stress produced bottom erosion and matter resuspension, and consequently major changes in the bathymetry. In addition, in situ sedimentary measurements carried out by Lopez-Jamar (1996) corroborate the bottom erosion in the main chanel of the estuary and at the end of the dock produced by the velocity increase generated by the building of the breakwater.
- A practical method for setting coastal water quality targets: harmonization of land-based discharge limits with marine ecosystem thresholdsPublication . Tosic, Marko; Martins, Flávio; Lonin, Serguei; Izquierdo, Alfredo; Dario Restrepo, JuanThe Caribbean Sea provides significant ecosystem services to the livelihood and well-being of countries in the region. Protection of the marine ecosystem requires policy on coastal water quality that considers ecologically-relevant thresholds and has a scientific foundation linking land-based discharges with seawater quality. This study demonstrates a practical method for setting local-scale coastal water quality targets by applying this approach to Cartagena Bay, Colombia, and setting targets for end-of-river suspended sediment loads to mitigate offshore coral reef turbidity. This approach considers reef thresholds for suspended sediments and applies a field-calibrated 3D hydrodynamic-water quality model (MOHID) to link the marine thresholds to fluvial loads. Monitoring data showed that suspended sediments were consistently above the coral reef ecosystem threshold of 10 mg/l, and the model adequately reproduced field observations. It was shown that ecosystem thresholds could be maintained within the extent of the bay by reducing suspended sediment loads in the Dique Canal from current load estimates of 6.4 x 10(3) t/d (rainy season) and 4.3 x 10(3) t/d (transitional season) to target loads of 500-700 t/d, representing reductions of similar to 80-90%. These substantial reductions reflect ongoing issues in the Magdalena watershed which has experienced severe erosional conditions and intense deforestation over the past four decades. The presented method is practical for countries without access to long-term datasets, and could be applied to other parameters or discharge types. The method is particularly beneficial for developing site-specific targets, which are needed considering the natural and anthropogenic variability between different coastal zones and water bodies.
- Integrating technologies for oil spill response in the SW Iberian coastPublication . Janeiro, João; Sepp Neves, Antonio Augusto; Martins, Flávio; Relvas, PauloAn operational oil spill modelling system developed for the SW Iberia Coast is used to investigate the relative importance of the different components and technologies integrating an oil spill monitoring and response structure. A backtrack of a CleanSeaNet oil detection in the region is used to demonstrate the concept. Taking advantage of regional operational products available, the system provides the necessary resolution to go from regional to coastal scales using a downscalling approach, while a multi-grid methodology allows the based oil spill model to span across model domains taking full advantage of the increasing resolution between the model grids. An extensive validation procedure using a multiplicity of sensors, with good spatial and temporal coverage, strengthens the operational system ability to accurately solve coastal scale processes. The model is validated using available trajectories from satellite-tracked drifters. Finally, a methodology is proposed to identifying potential origins for the CleanSeaNet oil detection, by combining model backtrack results with ship trajectories supplied by AIS was developed, including the error estimations found in the backtrack validation. (C) 2017 Elsevier B.V. All rights reserved.