Andrés F. Osorio

The Prestige Oil Spill in Cantabria (Bay of Biscay). Part I: Operational Forecasting System for Quick Response, Risk Assessment, and Protection of Natural Resources

Abstract In this paper, we present the operational forecasting system developed to assist in the response to the 2002 Prestige oil spill in Cantabria. The objective of the system developed was to forecast the wave climate, tidal and wind currents, and oil spill trajectories to provide a technical assessment to decision makers for a response to the oil spill. The two main components of the system were data collection and processing and integration with numerical models for forecasting. The information from overflights received daily became essential in achieving a correct initial position of the oil slicks. Meteorological and oceanographic data were also received daily by means of an emergency protocol established between Puertos del Estado (Spain), the Naval Research Laboratory (USA), and the University of Cantabria (Spain). These data were used to run the trajectory model, the wave propagation model, and the shallow depth-integrated flow model. The information generated by the numerical simulations was presented to the decision makers every day in the form of maps that were easy and quick to interpretation as a tool to help in the response planning. In addition, to develop a defensive or protection strategy for sensitive areas like estuaries and marshes, a hydrodynamic study was carried out by the University of Cantabria in all the estuaries of the region. The result of this study consisted of a boom deployment plan for each.

Long-Term Quantification of Beach Users Using Video Monitoring

Abstract Images from an Argus beach monitoring station were analyzed to count the number of people on two city beaches in Barcelona (NW Mediterranean) every hour for 4 years. Daily, weekly, seasonal, and interannual user distribution patterns were clearly established. Two different fit models were applied to the data based on a Fourier polynomial and nonlinear criteria, including external factors such as temperature and wind conditions, as well as predisposition factors. Finally, the evolution of beach users was compared with morphological beach changes caused by natural processes and human action. The results demonstrated that video observations provide a suitable method for counting people on the beach that could be useful for a number of coastal management applications.

Present and Future Challenges of Coastal Erosion in Latin America

ABSTRACT Silva, R.; Martínez, M.L.; Hesp, P.; Catalan, P.; Osorio, A. F.; Martell, R.; Fossati, M.; Miot da Silva, G.; Mariño-Tapia, I.; Pereira, P.; Cienfuegos, R.; Klein, A., and Govaere, G., 2014. Present and future challenges of coastal erosion in Latin America. The coastal zones of Latin America have many landforms and environments, including sedimentary cliffs, deeply incised estuaries, headlands, barrier coasts and low lying, muddy coastal plains. These forms will respond differently to the expected changes in climate and associated sea level rise, which may produce coastal erosion in the future. Considering the coasts of Latin America overall, erosion is not yet a serious threat, although it is widespread and it is severe in some parts. Major erosion problems are frequently associated with human intervention in sediment supply, with poor planning or with the morphodynamic nature of the coast. Permanent erosional processes, locally or regionally, are caused by tectonic subsidence, deforestation and the fragmentation of coastal ecosystems, land use changes and sediment deficits because of infrastructure built along the coast. In this article we analyse coastal erosion in Latin America and the challenges it presents to the region. We first highlight the relevance of Latin America in terms of its biodiversity; then we describe the population at risk, demographic trends and economic growth throughout the low lying coastal zones. We also examine the vulnerability of the region by analyzing the resilience of key coastal ecosystems after exposure to the most frequent hazards that affect coastal zones in Latin America, namely tropical cyclones, sea level rise, ocean acidification, earthquakes and tsunamis. Finally, we discuss seven case studies of coastal erosion across Latin America. We close the study by pinpointing the main areas of concern in Latin America and explore possible strategies to overcome erosion and thus sustain economic growth, minimize population risk and maintain biodiversity.

An algorithm for the measurement of shoreline and intertidal beach profiles using video imagery: PSDM

A critical factor when undertaking proper coastline management is the availability of reliable data, allowing those responsible to make informed decisions about land use and its impact on natural resources. Marine resource data (bathymetry, time-series of waves, coastal use levels, etc.) have often been difficult for policy-makers to obtain and use, given the high costs involved and difficulties in their application and interpretation. In cases where a source of coastline data is available, it is important that it be sufficiently complete to compare habitat changes (in morphology and use) that are only observable over a period of years. Thus, it is necessary to look for alternative methods to obtain this long-term information. The availability of new data-gathering techniques for the study of coastlines and coastal processes, such as remote sensors and underwater photography and videography, has increased during the last decade. One of the principal research applications of these techniques is bathymetry. This paper presents state-of-the-art image-based models that allow the construction of topo-bathymetric shore data. The Physical and Statistical Detection Model (PSDM), which constitutes the core of this research, is discussed and validated. The PSDM is based on a combination of six different algorithms that describe the shoreline features, and it assigns physical and statistical criteria to the detection process. In conclusion, a numerical tool based on video systems is introduced which shows great potential for monitoring coastal issues and supplying data to aid technicians and shoreline managers.

Environmental applications of camera images calibrated by means of the Levenberg-Marquardt method

Even though different authors have presented procedures for camera calibration in environmental video monitoring, improvements in the robustness and accuracy of the calibration procedure are always desired and in this work the Levenberg-Marquardt method is included in the camera calibration process for environmental video monitoring images as a way to improve the robustness of the camera calibration when a low number of control points is available without using laboratory measurements. The Pinhole model and the Levenberg-Marquardt method are briefly described and a four step camera calibration procedure using them is presented. This procedure allows users to use ground control points to estimate all the Pinhole model parameters, including the lens distortion parameters and its implementation results with laboratory data are compared with the results presented by other authors. The procedure is also tested with field data obtained with cameras directed toward the beaches of the city of Cartagena, Colombia. The results show that the procedure is robust enough to be used when just a low number of control points are available, even though a large number of GCP is recommended to obtain high accuracy.

Methodology to Correct Wind Speed during Average Wind Conditions: Application to the Caribbean Sea

AbstractThe spatial and temporal variability of ocean wind waves plays an important role in many engineering and environmental problems. Although research in this area has been improved in recent decades thanks to the emergence of satellite data, in many cases this information does not have the appropriate resolution for more detailed and local research. In view of this, reanalysis data developed by several meteorological agencies have appeared as a good alternative to force the most popular ocean wind-wave models. Thus, to achieve more accuracy in the data, the 60-yr Global Atmospheric Reanalysis 1 carried out by the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) has been corrected, employing the vector correlation and triple collocation theories combined with information from different accurate sources. The comparison of wind speed with satellite and in situ buoy data before correction reveals an important underestimation for areas near the Colombian c...

Numerical Study of Run-up Oscillations over Fringing Reefs

ABSTRACT Peláez-Zapata, D.S.; Montoya, R.D., and Osorio, A.F., 2018. Numerical study of run-up oscillations over fringing reefs. This work presents a numerical study of run-up oscillations over a typical fringing reef profile at the laboratory scale. The nonhydrostatic SWASH model was calibrated and validated using experimental data of free surface elevation for eight gauges and run-up oscillations. The model shows a high sensitivity to variations in the parameters of bottom friction and horizontal mixing length. A process of calibration found the optimal values to be 0.014 s m−1/3 and 0.01 m, respectively. With these values, the model is good at reproducing bulk run-up parameters such as the mean run-up period (r2 = 0.93), sea-swell significant run-up (r2 = 0.93), and infragravity significant run-up (r2 = 0.88). The ratio between the infragravity and sea-swell run-up is highly dependent on the surf similarity parameter. For dissipative and intermediate conditions, the run-up is mainly dominated by low-frequency or infragravity oscillations, whereas for reflective conditions, high-frequency or sea-swell oscillations become more important. The results show that the run-up spectrum at high frequencies is proportional to f−4. The energy level at high frequencies is apparently independent of the offshore wave conditions and the width of the reef flat. However, the depth of the reef crest seems to be the most influential variable on the high-frequency energy. A parametric equation that depends on both the energy level at high frequency and a function of the run-up period was obtained to analyze the spectral characteristics of the wave run-up. This equation can be considered a first approach to a general parameterization of the run-up spectrum for reef zones, which can be useful in coastal engineering applications, such as predicting both the run-up height and frequency, spectral response of sediment transport in the swash zone, and coupling with spectral wave models.

CFD modelling of wave damping over a fringing reef in the Colombian Caribbean

AbstractThe understanding of physical processes over submerged reefs represents an important ongoing research topic when considering wave energy dissipation and coastal protection that these environments provide. Detailed analyses are required to assess wave damping based on the contribution of reef roughness and wave breaking. For this purpose, the CFD (computational fluid dynamics) toolbox OpenFOAM® is applied to simulate the wave energy dissipation process over reefs with explicit accounting for the complexities of coral shape instead of commonly applied parameterized approaches for bottom roughness and wave breaking. Model validation was performed through comparison with field measurements over a reef profile of Tesoro Island in the Colombian Caribbean. Quantitative analysis of wave damping caused by wave breaking and reef roughness was conducted for (1) moderate and extreme wave conditions, (2) smooth and rough seabed configurations and (3) changes in the water depth over the reef crest. Wave height attenuation is found to vary along the reef profile reaching differences of up to 55% between smooth and rough reef surface scenarios, particularly for moderate wave conditions. Wave breaking, high turbulent flows and detachment of undertow currents are among the reef roughness effects on hydrodynamics. The fore-reef terrace and the reef crest are identified as the most critical zones where dissipation takes place. Wave breaking from rough seabeds provides a global wave attenuation of 75.4–94.8%, with the reef roughness alone accounting for ~ 4–14%. Under extreme wave height scenarios, the wave damping from reef roughness is not significant. Further predictions regarding roughness effects on the reef hydrodynamics, wave set-up and undertow currents for moderate and extreme wave climate conditions are also shown. Directions for future research using CFD are presented to address limitations that arise from the limited span-wise domain in our approach that prevents development of large lateral coherent structures.

A model for the weathering of Colombian crude oils in the Colombian Caribbean Sea

A model that describes the weathering of crude in an oil spill caused by interaction with the atmosphere and the ocean was developed. This model was adapted to the Colombian crudes Cusiana (°API43.2) and Vasconia (°API20.7). To calibrate the model, evaporation and emulsification experiments were carried out at conditions similar to those of an oil spill in the Colombian Caribbean Sea. The dependence of evaporation with wind velocity, not predicted by the state-of-the-art models, was captured by a correlation for the mass transfer coefficient calculated from the experimental data. Emulsification rate, maximum water content and required evaporation to form an emulsion were determined and their values explained considering the effect of wax precipitation for Cusiana crude oil. When compared to well-established weathering software, such as ADIOS, the proposed model predicts the weathering of Colombian oils in a way that better agrees with the experiments conducted in the laboratory.

Swash Oscillations in a Microtidal Dissipative Beach

ABSTRACT Conde-Frias, M.; Otero, L.; Restrepo, J.C.; Ortiz, J.C.; Ruiz, J., and Osorio, A.F., 2017. Swash oscillations in a microtidal dissipative beach. This paper evaluates the relationship between gravity and infragravity energy with swash oscillations as well as the models ability to reproduce the transformation of the wave as it approaches the shore on a dissipative beach. For this purpose, numerical experiments were conducted in a dissipative beach from Cartagena, Colombia. Mean free surface measurements were carried out for 2 days in February 2014 by installing a cross-shore array of pressure sensors, as well as a Fourier analysis from these measurements to identify frequency components that characterize the waves and the energy associated with them. To implement the numerical modelling, the SWASH model (The Simulation WAves till Shore is a numerical model that resolves nonlinear shallow-water equations) was set up by using the bathymetric profile of Bocagrande Beach obtained during the field campaign. The results of this numerical modelling enabled the study of the infragravity energy growth mechanism and the evolution of gravity energy as the wave approaches the shore, as well as the relationship between gravity and infragravity energy with swash oscillations. Overall, the results show that the model is able to reproduce the significant wave height and significant wave height associated with infragravity energy; moreover, the model is able to accurately describe processes of energy dissipation and energy transfer. Furthermore, through a spectral analysis applied to the swash oscillations time series it was possible to find that saturation occurs at low-frequency significant swash height and high-frequency significant swash height as the significant wave height increases, since its increase is not linear with respect to the signficant wave height incident.