Publications

Papers

Info Development of a Bayesian network-based early warning system for storm-driven coastal erosion

Coastal hazards such as flooding and erosion can cause large economic and human losses. Under this threat, early warning systems can be very cost-effective solutions for disaster preparation. The goal of this study was to develop, test, and implement an operational coastal erosion early warning system supported by a particular method of machine learning. Thus, the system combines Bayesian Networks, and state-of-the-art numerical models, such as XBeach and SWAN, to predict storm erosion impacts in urbanized areas. This system was developed in two phases. In the development phase, all information required to apply the machine learning method was generated including the definition of hundreds of oceanic synthetic storms, modeling of the erosion caused by these storms, and characterization of the impact levels according to a newly defined eerosion iimpact index. This adimensional index relates the distance from the edge of the dune/beach scarp to buildings and the height of that scarp. Finally, a Bayesian Network that acted as a surrogate of the previously generated information was built. After the training of the network, the conditional probability tables were created. These tables constituted the ground knowledge to make the predictions in the second phase. This methodology was validated (1) by comparing 6-h predictions obtained with the Bayesian Network and with process-based models, the latest considered as the benchmark, and (2) by assessing the predictive skills of the Bayesian Network through the unbiased iterative k-fold cross-validation procedure. Regarding the first comparison, the analysis considered the entire duration of three large storms whose return periods were 10, 16, and 25 years, and it was observed that the Bayesian Network correctly predicted between 64% and 72% of the impacts during the course of the storms, depending on the area analyzed. Importantly, this method was also able to identify when the hazardous conditions disappeared after predicting potential consequences. Regarding the Regarding the second validation approach, second validation approach, the k-fold cross-validation procedure was applied to the peak of a set of varying storms and it demonstrated that the predictive skills were maximized (63%

Year: 2024

Number Pages: 1-15pp.

Author(s): Garzon, J.L.; Ferreira, Ó.; PLOMARITIS, T.A.; Zózimo, A. C.; Fortes, C. J. E. M.; Pinheiro, L.

: Coastal Engineering

Editor: Elsevier

Volume: Vol 189 (104460).

DOI: https://doi.org/10.1016/j.coastaleng.2024.104460

Keywords: HIDRALERTA; Sandy beaches; Bayesian networks; Numerical modeling; Prediction system

Info Experimental study of an onshore dual chamber oscillating water column device

A wave flume is used to study a scaled model of a stepped bottom dual-chamber Oscillating Water Column (OWC) installed onshore. Compared to traditional single-chamber OWCs, the use of dual-chambers is expected to widen the range of sea states in which the OWC is more efficient, and the step, in front of the first chamber, boosts the capturing energy capacity of the device. The Power Take-Off (PTO) system is modelled as an air opening in the pneumatic chambers. Several experiments combining regular incident waves and PTO damping conditions are performed. Results of the amplitudes of the free surface elevations inside the chambers show that the device can amplify the incident wave amplitude up to 1.57 times in chamber 2. Results of the primary efficiency show that the device is highly dependent on the PTO damping characteristics and can reach around 40% for a wide range of wave periods. Results of the reflection analysis show that the reflection coefficient is also dependent on the PTO damping characteristics but remain lower than 0.6 for all the studied cases. Sloshing phenomenon (mostly in the cross-section direction) was observed for a wavelength close to the cross-section dimension, impacting negatively on the device pneumatic performance.

Year: 2024

Number Pages: 16p..

Author(s): Gadelho, J.; REZANEJAD, K.; Guedes Soares, C.; Santos, J. A.; Anastas, G.; Fortes, C. J. E. M.

: Ocean Engineering

Editor: Elsevier

Volume: Volume 300 (117240).

DOI: https://www.sciencedirect.com/science/article/pii/S0029801824005778

Keywords: Reflection coefficients; Efficiency improvement; Breakwater; Experiments; Oscillating water column

Info Numerical analysis of 3D hydrodynamics and performance of an array of oscillating water column wave energy converters integrated into a vertical breakwater

Info A RANS-based Numerical Model to Simulate Overtopping-type Wave Energy Converters Integrated into Breakwaters

Info An Early Warning System for Coastal Risks Assessment

Info Conceptual and quantitative categorization of wave

Info Damage Evolution in Physical Scale Model Tests of a Stretch of the Breakwater of Peniche Harbour.

Info Damage Evolution Prediction during 2D Scale-Model Tests of a Rubble-Mound Breakwater: A Case Study of Ericeira

Info Determination of Wave Run-Up Through the TimesTack Methology and hrough a Resistive Wave Gauge. a Comparative Analysis

Info Development of a Bayesian networks-based early warning system for wave-induced flooding

Coastal flooding prediction systems can be an efficient risk-reduction instrument. The goal of this study was to design, build, test, and implement a wave-induced flooding early warning system in urban areas fronted by sandy beaches. The system utilizes a novel approach that combines Bayesian Networks and numerical models (SWAN + XBeach) and was developed in two phases. In the development phase, firstly, the learning information was generated including the creation of oceanic conditions, modeling overtopping discharges, the haracterization of the associated im pacts (no, low, moderate and high) in pedestrians, urban components and buildings, and vehicles, and secondly, the Bayesian Networks were designed that surrogated the previously generated information. After their training, the conditional probability tables were created representing the foundation to make predictions in the operational phase. This methodology was validated for several historical events which hit the study area (Praia de Faro, Portugal), and the system correctly predicted the impact level of around 80% of the cases. Also, the predictive skills varied depending on the level, with the no and high impact levels overcoming the intermediate levels. In terms of efficiency, one simulation (deterministic) of coastal flooding for 72 h by running SWAN + XBeach operationally would take more than two days on a one-logical processor workstation, while the current approach can provide quasi-instantaneously predictions for that period, including probability distributions. Moreover, the two-working phase approach is very flexible enabling the inclusion of additional features such as social components representing a powerful tool for risk reduction in coastal communities.

Year: 2023

Number Pages: 19p..

Author(s): Garzon, J.L.; Ferreira, Ó.; Zózimo, A. C.; Fortes, C. J. E. M.; Ferreira, A. M.; Pinheiro, L.; Reis, M. T. L. G. V.

: International Journal of Disaster Risk Reduction

Editor: Elsevier

Volume: Volume 96.

DOI: https://doi.org/10.1016/j.ijdrr.2023.103931

Keywords: Wave overtopping; Sandy beaches; Bayesian network; XBeach; Prediction system

Comunicação

Info Progress Status of PO-NAVIGATION Project

Info Shear waves over longshore nonuniform barred beaches

Info Southern protection dike of the embankment connecting Macao International Airport to the New City of Cotai. Wave disturbance scale model tests

Info The VTMIS Concept and Related Projects. Application to the Port of Sines Situation

Info Trapped and free-wave propagation in channels and harbours

Capítulo de Livro

Info Multi-functional artificial reefs for coastal protection

Tese de Doutoramento

Info Trapped-mode propagation along irregular coasts

Info Probabilistic Assessment of the Safety of Coastal Structures

Info Unsteady Nearshore Currents on Longshore Varying Topographies

Info Simulação da agitação irregular. Técnicas matemáticas

Relatório Científico

Info Síntese dos dados de agitação marítima existentes no LNEC.

Info Valores extremos da agitação marítima. Viana do Castelo - Tratamento local dos dados existentes.

Info Aeroporto Internacional de Macau. 3 - Estudos de estabilidade. Relatório 3.1 - Ensaios de estabilidade e galgamentos do perfil da obra aderente de protecção ao terminal do aeroporto.

Info Aeroporto Internacional de Macau. 3 - Estudos de estabilidade. Relatório 3.2 - Ensaio de estabilidade e galgamentos do perfil da protecção este do aterro da pista do aeroporto.

Info Aeroporto Internacional de Macau. Comentários ao documento do MIAC 'Design water levels and return periods of extreme events'.

Info Aeroporto Internacional de Macau. Comentários aos documentos anexos aos ofícios do LECM n.º 103 de 90.02.10 e n.º 151 de 90.02.17.

Info Aeroporto Internacional de Macau. Estudos de agitação marítima. Relatório 2.4 - Considerações suplementares sobre níveis do mar e alturas de onda.

Info Aeroporto Internacional de Macau. Projecto do modelo físico hidráulico dos estudos de agitação marítima.

Info Ajustamento gráfico de distribuições.

Info As Provas de Governo e Manobra do N/T "Bornes". Relatório Final

Outro

Info Relato da missão a Bruxelas (28 a 30 de Outubro de 1998) para participação na 10ª Reunião da Acção Concertada Added Value Services in VTMIS do Programa Comunitário de I&D TRANSPORTS . Relatório efe

Info Short-term stochastic numerical and physical simulation of sea waves - Proposta de Projecto de Investigação apresentada ao Programa PRAXIS XXI, na área científica de Engenharia Civil

Info Transformações Não-Lineares de Ondas Marítimas em Zonas Costeiras - Proposta de Projecto de Investigação apresentada ao Programa PRAXIS XXI , na área científica de Engenharia Civil

Info V Programa Quadro da União Europeia. Preparação da discussão dos Programas Específicos. Documento de trabalho da Comissão (COM (97) 553 Final). Grupo de Trabalho 6 Sustainable Mobility and Intermod

Info Valores extremos da agitação marítima no Algarve - Proposta de Projecto de Investigação apresentado ao Programa de Intervenção nos Laboratórios do Estado (MCT-FCT), sub-projecto Valorização e Protec