Coastal nourishment scenarios for the Ovar coastline, Portugal

The study area encompasses a dynamic and fragile 16.5 kilometre sandy open coast on Portugal's north-west shelf. The wave climate is highly energetic with average significant wave heights of 2-3 metres, increasing to over 8 metres during storms originating from the North Atlantic between October and March. Littoral drift moves approximately 1.1 million cubic metres annually from north to south. Current erosion rates average 1.2 metres per year by 2050 and 1.8 metres per year by 2100 under projected sea level rise conditions. The coastline includes urbanised settlements at Esmoriz, Cortegaça/ Maceda, and Furadouro, requiring protection of inhabited areas while considering opportunities for ecological restoration and relocation where appropriate.

To develop and evaluate climate change adaptation pathways for the Ovar coastline through integrated physical and economic analysis, supporting evidence-based decision-making for coastal management that balances erosion mitigation, economic viability, stakeholder preferences, and ecosystem service values over an 80-year time horizon.

Challenges addressed

The main challenge is environmental management of severe coastal erosion. The measures also reduce natural hazard risk from shoreline retreat and support climate change adaptation by lowering the risk of coastal flooding.

Costs of NbS

The study assesses artificial beach nourishment, combined with dune restoration, along 16.5 km of the highly erosion-prone Ovar coastline in Aveiro. The measures are planned as climate adaptation pathways for 2020–2100 and have not yet been implemented. In the selected scenario (C3.2), a T-groin is built at Furadouro at the start, and from year 30 a 2 km stretch is nourished every five years with 1–2 million m³ of sand, 16 million m³ in total. The T-groin costs about EUR 5.0 million, while the recurring nourishment and extra maintenance of the groin add about EUR 14.9 million. Total costs come to about EUR 19.9 million over 80 years (2023 prices, 3% discount rate).

Under a high-emission future (SSP3), the scenario limits territorial loss and slows shoreline retreat, sharply reduces damage from overtopping and flooding, and lowers maintenance of existing coastal defences. It also helps conserve the natural coastal landscape and its ecosystems, and supports beach-related businesses. Together these benefits are worth about EUR 41.0 million by 2100 (2023 prices, 3% discount rate).

Benefit–cost ratio

The BCR of 2.0 means each euro invested returns about two euros, with the investment breaking even around 2051. Combining a T-groin with moderate, less frequent nourishment made C3.2 the best-performing of the twelve scenarios tested; results depend strongly on where, how often and how much sand is placed.

Three sequential participatory workshops engaged stakeholders: first workshop selected top ten coastal erosion mitigation measures and validated impacts; second workshop developed shared territorial visions including protection of occupied areas and relocation of at-risk communities; third workshop created comprehensive adaptation pathways mapping. The LTC numerical model simulated shoreline evolution using bathymetry, wave climate data, and sea level rise projections (1.125 cm/year). The COAST tool performed lifecycle cost-benefit analysis calculating net present value, benefit-cost ratios, and break-even years for each scenario. Meta-analytic function transfer estimated local ecosystem service values using global ESV functions calibrated to Portuguese socioeconomic conditions under Shared Socioeconomic Pathways SSP3 and SSP5 scenarios.

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Study overview

The Ovar Municipality coastal stretch on Portugal's western coast is one of the country's most erosion-prone and vulnerable areas, with historical erosion rates reaching 6 metres per year over the past 50 years. The INCCA research project developed a comprehensive approach to evaluate climate change adaptation pathways for this 16.5 kilometre sandy coastline between Esmoriz and Torraão do Lameiro, integrating participatory stakeholder processes with physical modelling and economic analysis.

Sixteen coastal defence structures, including six groins and seven longitudinal revetments, currently protect the shoreline but require ongoing maintenance. Under a business-as-usual baseline scenario with no additional interventions, the shoreline is projected to retreat approximately 290 metres by 2050 and 500 metres by 2100, corresponding to territorial losses of 60 hectares and 248 hectares respectively. Economic losses from this baseline scenario are anticipated to exceed 150 million euros by the end of the century.

Twelve adaptation pathway scenarios were developed through three participatory workshops involving local stakeholders, then evaluated using the LTC numerical shoreline evolution model and the COAST cost-benefit analysis tool. Scenarios tested various combinations of artificial sand nourishment (adding 1-3 million cubic metres of sediment), structural modifications including groin removal and T-groin implementation, and differing frequencies of nourishment intervention from annual to every five years.

The analysis revealed that while scenarios with larger sediment volumes delivered better physical performance in terms of reducing territorial loss, they did not necessarily achieve the best economic outcomes. Six of twelve scenarios achieved economic viability over the 80-year analysis period, demonstrating that optimal solutions depend on balancing design parameters, land use values, and ecosystem service considerations.