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Óscar Ferreira

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Uncertainty Analysis Related to Beach Morphology and Storm Duration for More Reliable Early Warning Systems for Coastal Hazards

Journal of Geophysical Research Oceans (2023)

Juan L. Garzon Theocharis A. Plomaritis Óscar Ferreira

Abstract Early warning systems (EWSs) for coastal erosion are cost‐effective instruments for risk reduction. Among other aspects, the selection of the pre‐storm beach morphology and the definition of storm characteristics can affect EWS reliability. Here, XBeach simulations were used to assess the uncertainties in beach‐dune erosion related to the variability of storm severity and duration and pre‐storm morphology. Wave height return periods (from 5 to 50 years) determined the severity and the duration variability was established from confidence intervals after an adjustment with wave height. The variability of steep profiles included different berm morphologies (from fully developed to eroded berms). Three indicators, relative eroded volume, proportional berm retreat and proportional dune retreat, were evaluated. The experiments revealed that: (a) Relative eroded volume uncertainties related to the pre‐storm morphology variability were slightly lower (maximum 8%) than the uncertainties related to storm duration (11%–18%). (b) Pre‐storm profile variability can induce large uncertainties in the proportional berm retreat (up to 88%) for moderate events such as the 5‐ and 10‐year events. Storm duration variability had less influence on this indicator (maximum 12%). (c) The uncertainties in the proportional dune retreat increased with storm severity and they ranged between 14% and 41% for pre‐storm profile variability and between 2% and 40% for storm duration variability. Duration variability even governed the occurrence of dune breaching on eroded berm profiles in the most extreme event. Hence, the uncertainties related to initial/forcing conditions, namely pre‐storm morphology and storm duration, must be assessed to develop reliable coastal erosion EWSs.

Berm

10.1029/2022jc019339

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Citations (4)

River discharge data from hydrographic station Pulo de Lobo, 2008-03-19 to 2014-04-07

Erwan Garel Óscar Ferreira

Hydrographic survey

10.1594/pangaea.845746

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Citations (0)

Bridging the gap between resilience and geomorphology of complex coastal systems

Earth-Science Reviews (2019)

Katerina Kombiadou Susana Costas A. Rita Carrasco Theocharis A. Plomaritis Óscar Ferreira

Confusion

Resilience

10.1016/j.earscirev.2019.102934

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Citations (45)

A Coastal Risk Assessment Framework Tool to Identify Hotspots at the Regional Scale

American Geophysical Union eBooks (2016)

Ap van Dongeren Christophe Viavattene José A. Jiménez Óscar Ferreira Annelies Bolle

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Citations (1)

Artificial Construction of Dunes in the South of Portugal

Journal of Coastal Research (2005)

Ana Matias Óscar Ferreira Isabel Mendes João Alveirinho Dias Ana Vila‐Concejo

The Cacela Peninsula on the south coast of Portugal was, previous to nourishment operations, extremely vulnerable to overwash events. During the 1995–96 winter, extensive overwashing led to the opening of a new inlet. Simultaneously, the lagoon channel in the backbarrier was silting up with the overwash deposits, inlet flood delta sands, and accretion of fine sediments. Between October 1996 and February 1997 the channel was dredged, and the sediments were deposited on the western 2,000 meters of the Cacela Peninsula, forming an artificial dune ridge. The sediment characteristics of the dredge spoils were in contrast with the natural dune sand. The spoils had higher silt and clay content, lower mean grain size, and poorer sorting. In January 1998, three washover breaches were infilled, with sand removed from the foreshore, on the eastern part of the Cacela Peninsula. These sands were coarser and more poorly sorted than the original dune sediments. A 2-year monitoring program, consisting of beach/dune profiling, topographic surveys in specific areas, and sediment analysis, was established to observe the morphological evolution of these areas. The total eroded volume recorded for the dune nourishment project after 2 years was about 106,500 cubic meters, corresponding to 33% of the total 325,000 cubic meters of sediment that was deposited. The washover infilling showed little or no variation. However, the downdrift beaches and foredunes experienced severe erosion. Both protective measures accomplished their purposes in terms of preventing erosion; however, a natural landscape was only created where dune development by aeolian processes was possible.

Overwash

Peninsula

Coastal erosion

Silt

Foredune

Siltation

10.2112/03-0047.1

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Citations (56)

Multi-year high-frequency current and water quality in-situ observations at the Guadiana Estuary

Erwan Garel Óscar Ferreira

10.1594/pangaea.845750

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Citations (1)

An Irregular Wave Propagation Model Application to an Open Coastal Area

Journal of Coastal Research (2007)

Ana Catarina Zózimo C. J. E. M. Fortes M. G. Neves Óscar Ferreira J. L. M. Fernandes

In this paper the DREAMS_CR_S model for propagation and deformation of random waves (characterized by a directional spectrum) over regions of variable depth is described. It is based on the linear superposition of the wave fields obtained from a monochromatic wave model for several frequency–direction components in which the incident directional spectrum is discretized. The model predicts the effects of refraction, diffraction, shoaling, reflection, and wave breaking. The model was applied to a real case—the Ancão Inlet at Ria Formosa, in Algarve (Portugal). Incident wave model conditions were chosen from measurements by a directional buoy, deployed over the seabed at −25 m depth below chart datum. The results illustrate that the model without breaking is working well and can be applied to areas with complex bathymetry. When breaking is taken into account, the results are not very accurate. The wave-breaking iterative process and the estimation of the breaking point used in the model have to be improved.

Buoy

Reflection

Shoaling and schooling

Electromagnetic spectrum

10.2112/04-0192.1

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Citations (0)

Evaluation of sedimentological and morphological changes induced by the rehabilitation of sandy beaches from the Ria Formosa barrier island system (South Portugal)

Thalassas An International Journal of Marine Sciences (2014)

Mohamed Achab Óscar Ferreira João Dias

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Citations (14)

Unforeseen cascading effects of an inlet opening

Scientific Reports (2024)

Óscar Ferreira

The opening of the Cacela Inlet (southern Portugal) in 2010 led to unforeseen effects observed after 2017, including an extreme acceleration of the retreat of the inland lagoon margin from about 0.2 to 2 m/year. This was a consequence of the development of a large flood delta in an area of limited accommodation space, forcing the main tidal channel to move inland. The coastal retreat currently affects a flat sandy area that separates the old and inactive Cacela cliff from the lagoon. Between 2025 and 2030, the currently inactive Cacela cliff is likely to become active again, posing a potential risk of damage to a medieval fortress and the existing settlement of Cacela Velha, an unforeseen cascading effect of the opening of the inlet. In order to prevent instability and damage to this legally protected area of national and public interest, several coastal management measures will be required.

Cliff

Settlement (finance)

10.1038/s41598-024-63467-0

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Citations (0)

Overwash vulnerability assessment based on long-term washover evolution

Natural Hazards (2009)

Tiago Garcia Óscar Ferreira Ana Matias João Alveirinho Dias

Overwash

Vulnerability

10.1007/s11069-009-9463-3

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Citations (24)