Morphological Development and Behaviour of a Shoreface Nourishment in the Portuguese Western Coast

Journal of Marine Science and Engineering

Celso Aleixo Pinto¹  Paulo Alves Silva²  Joaquim Pais-Barbosa²  Paulo Baptista³  Diogo Mendes⁴  Rui Taborda⁵  César Andrade⁵ 

[1] Coastal Monitoring and Risk Division, Portuguese Environment Agency (Agência Portuguesa do Ambiente), 2610-124 Amadora, Portugal;Departamento de Física e Centro de Estudos do Ambiente e do Mar (CESAM), Campus de Santiago, Universidade de Aveiro, 3810-193 Aveiro, Portugal;Departamento de Geociências e Centro de Estudos do Ambiente e do Mar (CESAM), Campus de Santiago, Universidade de Aveiro, 3810-193 Aveiro, Portugal;HAEDES, Casais do Arrocho, 2025-452 Azóia de Cima, Portugal;IDL—Instituto D. Luiz, Departamento de Geologia, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal;

关键词: wave dominated coast;    coastal erosion;    shoreface nourishment;    cross-shore and longshore processes;    coastal protection strategy;   

DOI  :  10.3390/jmse10020146

来源: DOAJ

【 摘 要 】

Current coastal protection strategy in Portugal defines beach and shoreface nourishment as a valid measure to mitigate coastal erosion in some erosional hot-spots, being considered as an adaptation measure under the present climate change scenario, including the impacts of sea level rise. However, scant objective data on shoreface nourishments are available to evaluate performance of this type of intervention in mitigating beach erosion and managing coast risk. We present the first monitoring results of a ≈2.4 × 10⁶ m³ shoreface nourishment on the Aveiro coast (Costa Nova—Ílhavo), the largest until now in Portugal, focusing on its morphological development, impacts on adjacent beaches due to alongshore spreading and cross-shore redistribution, and contribution to the sediment budget of the nourished sediment cell. The analyses are based on high-resolution coastal monitoring data, provided by the Portuguese COaStal MOnitoring Program (COSMO). A Multiple Monitoring Cell (MMC) approach was used to evaluate local and feeder efficiency of the nourishment, sediment budget exchanges within both the placement and wider survey domains (≈1 km² and 12 km², respectively). Results show rapid (ca. 6 months) morphological change over the placement area, with a decrease of about 40% of the initial volume. Fast onshore sediment redistribution explains part of this change, placed sand having merged with the pre-existing bar system increased the volume of the shallower nearshore. Longshore transport is reflected by increasing the robustness of the bar downdrift of the placement area and also explains the negative sediment budget (0.75 × 10⁶ m³) of the survey domain, which corresponds to losses through its southern boundary. Sediment spreading also induced accretion of the subaerial section of Costa Nova beaches in front of the placement area, reversing their long-term erosive trend. In contrast, this trend persisted at downdrift beaches. This suggests that the time lag of the subaerial beach response to this intervention increases with the distance to the placement area, and reversal of the erosive trend will only be noticeable in the following years. This study provides new insights on the time scales of beach response to high-magnitude shoreface interventions in high-energy wave-dominated sandy coasts, which will support decision making regarding similar operations designed to manage erosional hot-spots elsewhere.

【 授权许可】

Unknown