João Miguel Dias

Tidal propagation in Ria de Aveiro Lagoon, Portugal

Abstract Ria de Aveiro is a shallow vertically homogeneous lagoon, located in the Northwest of Portugal, connected to the Atlantic through a very narrow artificial channel, and supplied with freshwater by two major rivers, Antua and Vouga. The present study describes the application of a twodimensional depth integrated mathematical model, to predict tide-induced water level and depth mean current for the entire lagoon. The model computes time series of those variables as well as their instantaneous distribution at different times of the tidal cycle. Properties of tides and tidal currents in Ria de Aveiro are characterized and discussed. Special emphasis is given to the study of the hydrodynamic behaviour of the lagoon in extreme conditions of astronomical tide forcing, considering spring and neap tide conditions. Tides propagate from the mouth of Ria de Aveiro and are present in the entire lagoon. The tidal amplitude decreases with the distance from the mouth while the phase lag in the high and low water (which is different) increases. The tidal range increases for the spring tide at the far end of the channels correspond to a local increase of the high tide level, which result in a fortnightly variation of the mean levels at those places.

FAtiMA Modular: Towards an Agent Architecture with a Generic Appraisal Framework

This paper presents a generic and flexible architecture for emotional agents, with what we consider to be the minimum set of functionalities that allows us to implement and compare different appraisal theories in a given scenario. FAtiMA Modular, the architecture proposed is composed of a core algorithm and by a set of components that add particular functionality (either in terms of appraisal or behaviour) to the architecture, which makes the architecture more flexible and easier to extend.

Implementation and assessment of hydrodynamic, salt and heat transport models: The case of Ria de Aveiro Lagoon (Portugal)

Ria de Aveiro is a shallow coastal lagoon located in the Northwest coast of Portugal. The implementation and the assessment (calibration and validation) of the hydrodynamic, salt and heat transport models for Ria de Aveiro lagoon is presented. During the calibration the models parameters were adjusted to give the best fit of the model results to the field data. The hydrodynamic model calibration was carried out by comparing measured and predicted time series of sea surface elevation for 22 stations. The root-mean square of the difference between those values was determined and harmonic analysis was performed in order to evaluate the model ability to reproduce the tide propagation along the main channels of Ria de Aveiro. Validation of the hydrodynamic model was performed comparing measured and predicted sea surface elevation values for 11 stations, as well as velocities in the main flow direction for 10 stations and water flows for 6 stations. The salt and the heat transport models were calibrated comparing measured and predicted time series of salinity and water temperature for 7 stations. These models were validated comparing the model results with an independent field data set. Results indicate that the hydrodynamic, the salt and the heat transport models for Ria de Aveiro were successfully calibrated and validated.

Hydrological characterisation of Ria de Aveiro, Portugal, in early summer

The hydrologkal features of Ria de Aveiro, a coastal lagoon on the northwest Atlantic coast of Portugal, were investigated in two sampling surveys carried out between 316 and 2416197 and between 2916 and 717197, respectively. There was a significant freshwater inflow into the lagoon during the first survey, especially in the first days, due to the recent rain- falls. Records concerning water level, salinity, temperature and current velocity were performed at several stations located along the four main channels of the lagoon. The type of tide at the mouth was determined and was observed that astro- nomical tide is the main fiorcing agent driving water circulation in Ria de Aveiro. The tide at the mouth is semidiurnal and the tidal wave propagation in the lagoon has the characteristics of a damped progressive wave. Typical estuarine longi- tudinal salinity and temperature gradients connected with the distance to the mouth were identified, whereas vertical and transverse gradients were found unimportant, except in the frontal zone between oceanic and fresh water masses. Accord- ing to the results, even though Ria de Aveiro should be considered as vertically homogeneous, some channels may reveal characteristics of a partially mixed estuary, depending on the freshwater input. 0 1999 Ifremer / CNRS / IRD / Editions scientifiques et medicales Elsevier SAS

Lagrangian transport of particles in Ria de Aveiro lagoon, Portugal

Abstract A two-dimensional vertically integrated hydrodynamic model coupled to a particle tracking model is applied to study the dispersion processes and residence time in Ria de Aveiro lagoon (Portugal). The only dispersion process that is considered in this study is the advection, according to the main characteristics of the local hydrodynamic. The particle tracking model computes the particles position at each time step, using a fourth-order Runge-Kutta integration method. The dispersion of passive particles released along the lagoon and in critical areas are studied in this work. The residence time is also determined for the entire lagoon. The results show that the mixture between particles coming from different channels of the lagoon is negligible in a time scale higher than 2 tidal cycles. The residence time for the lagoon central area is about 2 days, revealing a strong marine influence in this area. At the upper reaches of the channels were found values higher than 2 weeks.

Numerical modeling of the impact of the Ancão Inlet relocation (Ria Formosa, Portugal)

This work describes the application of hydrodynamic (ELCIRC) and transport (VELA and VELApart) models to the Ria Formosa lagoon (Portugal) to study the impact of the relocation of the Ancao Inlet. Located in the south of Portugal, this lagoon is a mesotidal barrier island system that communicates with the sea through 6 inlets. The Old Ancao Inlet was artificially closed and the New Ancao Inlet was relocated into a westward position. This work investigates the hydrodynamic patterns and the potential pathways of tracers in Ria Formosa in two distinct configurations: before and after the Ancao Inlet relocation. The hydrodynamic model was successfully calibrated and validated against elevation, velocity and inlet discharges data, accurately reproducing the tidal propagation. The inlet relocation increases the magnitude of tidal currents, residual velocities and the tidal prism across the bar, suggesting a better stability. The tracers transport simulations suggest enhanced water exchanges through the Ancao Inlet and smaller residence times in the western part of Ria Formosa with the present configuration. Overall, it is concluded that the Ancao Inlet relocation had a positive contribution towards increasing the water renewal of the western part of the lagoon, thus decreasing its vulnerability to pollution.

Short Note: Application of the Mohid-2D model to a mesotidal temperate coastal lagoon

1. IntroductionA mathematical model can be considered as anapproximate reconstruction of a real phenomenon.All parameterizations and approximations used inmodels lead to deviations of the model results fromnature. It is an accepted requirement that anumerical model of estuarine hydrodynamicsshould be verified, calibrated and validated beforeused in a practical application. However, theprocedures to perform these tasks are not widelyaccepted (Cheng et al., 1991). Calibration andvalidation methods appear in several forms, de-pending on data availability, water mass character-istics and researchers’ opinion (Hsu et al., 1999).In this work, the Mohid-2D model implementa-tion for the Ria de Aveiro lagoon is presented,describing its assessment through calibration andvalidation against several different data sets. Due tothe lagoon complex geometry and the large numberof calibration stations used, this goal constitutes avery challenging task.The model is calibrated using as a first approach aqualitative comparison of the temporal evolution ofsea surface elevation (SSE) data measured in 1987/1988 at several locations. When a good match isobtained for all stations, the model’s accuracy isevaluated through the determination of the rootmean square (RMS) error and also through thecomparison between amplitude and phase of themain tidal constituents determined from harmonicanalysis of the observed and computed data. Thevalidation procedure is performed using two in-dependent data sets, which includes observations ofcurrent velocities and SSE values (1997 data) andmeasured water fluxes at the lagoon’s inlet for theperiod of October 2002.2. The study areaRia de Aveiro (Fig. 1) is a shallow mesotidallagoon located in the Northwest coast of Portugalð40 38

FED-the free body diagram method. Kinematic and dynamic modeling of a six leg robot

The free body diagram method, based on the dynamic equations of isolated rigid bodies, is used to overcome the difficulties in dynamic modeling of legged robots. The article presents a simulator for a six leg machine. Both kinematic and dynamic models are developed. Kinematic equations are derived with the Denavit-Hartenberg method. The free body diagram method is used to obtain the dynamic model. Some results of simulation are presented.

Influence of tides and river inputs on suspended sediment transport in the Ria de Aveiro lagoon, Portugal

Abstract In this work the influence of tides and river inputs on suspended sediment distribution in the Ria de Aveiro, a shallow lagoon situated in the Northwest of Portugal, has been studied. Particular emphasis has been placed on Laranjo Bay, a sub-system of the lagoon from a bio-geophysical point of view. The study is based on both data analysis and sediment transport modelling. Tides are the major factor influencing the hydrodynamics of the lagoon. Their effects are important even at the upper reaches of the different channels, where salinity, temperature and sediment concentrations change during the tidal cycle. Sediment concentration shows both semi-diurnal and fortnightly periodicity. Highest values are found in the northern channels due to erosion induced by high current speeds in shallow areas. Erosion and deposition are the dominant processes determining suspended sediment transport in the lagoon.

Flooding assessment under sea level rise scenarios: Ria de Aveiro case study

ABSTRACT Lopes, C., Azevedo, A., Dias, J.M., 2013. Flooding assessment under sea level rise scenarios: Ria de Aveiro case study Sea level rise is an important consequence of climate change with a significant impact on society and ecosystems. The present work aims to assess the sensitivity of Ria de Aveiro marginal flooded area to the sea level rise. A previous version of the hydrodynamic model ELCIRC was improved extending its numerical grid through the inclusion of the intertidal areas and the marginal topography. The present configuration was calibrated comparing model predictions with sea surface elevation data recorded at ten stations distributed throughout the lagoon. The root mean square error and the SKILL were computed, and generally an excellent/good agreement between predicted and observed sea surface elevation data was found. Once calibrated, the model was used to simulate the lagoon flooded area under present mean sea level and under two local sea level rise scenarios (0.42 m and 0.64 m), considering mean and spring tide conditions. In average was found an increase of 22% and 35% of the lagoon flooded area, respectively, relatively to the present. Additionally, an increase of 15% and 23% was found for the tidal prism at the inlet, for sea level rise scenarios of 0.42 m and 0.64 m, respectively. Numerical results evidenced that sea level oscillations induce important changes in the lagoon flooded area as well as on the local hydrodynamics. Consequently some activities developed in the lagoon margins may be in jeopardy, i.e. the agricultural fields located at the margins of S.Jacinto channel will be inundated by saltwater, if these sea level rise projections are confirmed.