Abstract
Due to economic, environmental, and social interest of coastal areas, together with their erosion problems, different coastal management strategies can be considered, with different physical (shoreline evolution) and economic (net present value, ratio benefit-cost, break-even point) consequences and impacts. Therefore, this work presents an integrated methodology that aims to compare and discuss the most promising coastal intervention scenarios to mitigate erosion problems and climate change effects, considering costs and benefits related to each intervention. The proposed methodology takes a step forward in assessing the coastal erosion mitigation strategies, incorporating three well-defined and sequential stages: shoreline evolution in a medium-term perspective; structures pre-design; and a cost-benefit assessment. To show the relevance of the methodology, a hypothetic case study and several intervention scenarios were assessed. In order to mitigate costal erosion two different situations were analyzed: the reference scenario and the intervention scenarios. 34 intervention scenarios were proposed and evaluated to mitigate the erosion verified. Depending on the parameter considered (reduce erosion areas, protect the full extension of urban waterfronts, improve the economic performance of the intervention by increasing the net present value, the benefit-cost ratio or decreasing the break-even time), best results are obtained for different scenarios. The definition of the best option for coastal erosion mitigation is complex and depends on the main goal defined for the intervention. In conclusion, costs and benefits analysis are demanded and it is considered that the proposed methodology allows choosing better physical and economic options for future coastal interventions, helping decision-making processes related to coastal management.
Highlights
Worldwide, coastal zones experience increased rates of erosion, mainly due to fluvial sediment supply reduction, as well as coastal areas degradation and transformation due to anthropogenic actions [1,2,3,4,5]
Final remarks highlight the major outlines of this section, which intended to describe the type of analysis that can be developed by applying the proposed methodology
Groin baseline scenario (Figure 6) shows that the groin impact on the shoreline evolution is positive at updrift, resulting in 2.4 ha accretion area
Summary
Coastal zones experience increased rates of erosion, mainly due to fluvial sediment supply reduction, as well as coastal areas degradation and transformation due to anthropogenic actions [1,2,3,4,5]. As described in [13,14,15], the IPCC (Intergovernmental Panel on Climate Change) identified three main strategies to respond to coastal erosion, flooding and sea level rise risks: i) retreat, limiting the effects of a potential dangerous event, landward resettling of the risky population centres and economic activities; ii) accommodation, considering all the strategies necessary to increase the society's resilience to coastal erosion, including land use change, emergency planning and hazard insurance [16,17,18]; iii) protection, involving all defence techniques used to preserve vulnerable areas, such as population centres, economic activities and natural resources; and iv) attack, by land reclamation and extending facilities towards the sea [19]. Some erosion impacts can be mitigated through coastal protection works, such measures may represent negative second order impacts for coastal environments and social and economic life [21]
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