Carlos Coelho

Erosion risk levels at the NW Portuguese coast: the Douro mouth—Cape Mondego stretch

The entire northwestern coast of Portugal is undergoing severe erosion and there are several areas at high risk of erosion. Commonly considered as a problem—because it jeopardizes human development along the coast—erosion is indeed a natural process of sediment redistribution. This paper presents a brief analysis of erosion driving forces and the subsequent state of vulnerability that coastal segments between the mouth of the River Douro and Cape Mondego are facing. The paper also discusses erosion risk levels, low or high, and the subsequent questions whether there are populations, economical assets or natural habitats at risk and/or areas prone to coastal flooding. Main challenges and future trends along the study area are identified in the light of understanding the underlying causes of conflicts and what realistically can be achieved given the morphodynamics and hydrodynamic processes, human development established along this coastal segment and the existing policies.

A Vulnerability Analysis ApproachFor The Portuguese West Coast

Coastal dynamics and erosion processes may cause serious damage, especially to people and assets in urban fronts, and they therefore merit special attention. To diminish the effects of these natural dynamics on coastal areas it is necessary to understand the various processes involved. The classification of a coast in terms of vulnerability and risk will only be possible when foresight capacity is improved, making the planning and decision processes easier. Coastal zone vulnerability to energetic environmental actions (waves, tides, winds and currents) may be considered to be biophysical systems sensitivity and morphological changes as the response. The present changes in the frequency of extreme events, the weakening of river sediments supply, the generalized sea level rise and other climatic changes, together with the advance of urban fronts towards the sea, may worsen the consequences of floods and land loss. The vulnerability analysis of coastal zones is crucial for appropriate land use, and is a complex process which involves many parameters. As a first approach an effective methodology is proposed and applied to the coastal region of the Aveiro district, south of Porto, Portugal, where the volume of available sediment is currently deficient in relation to the transport capacity, and it is predictable that the erosion situation will become further aggravated in some regions. This methodology consists of obtaining a global vulnerability index, which results from the weighting of each independently classified vulnerability parameter. This approach is complemented with a coastal line evolution estimation using numerical modelling.

Participation, scenarios and pathways in long-term planning for climate change adaptation

Abstract This article describes a climate change adaptation planning process triggered by a group of researchers and stakeholders in a context where no collective responses or long-term plans for protecting a vulnerable coastal system had been initiated, despite local perceptions of vulnerability and risk. The case study shows the application of two methods: scenario workshops and adaptation pathways in the context of a participatory action research methodological design. Participatory action research and qualitative scenario methods are highlighted as accelerators of climate change adaptation processes by calling to action, facilitating and connecting diverse social groups with a stake in a long-term plan towards a more adapted society. The experience leads to the conclusion that planning climate change adaptation has to go far beyond the technical dimension and take into account those affected (in the present and the future) by decisions made. A holistic approach to climate change adaptation planning will depend on the interrelations of managerial and top-down approaches with localized initiatives driven through an inclusive and collective action research process.

Influence of climate change on the Ria de Aveiro littoral: adaptation strategies for flooding events and shoreline retreat

ABSTRACT Dias, J.M., Lopes, C.L., Coelho, C., Pereira, C., Alves, F.L., Sousa, L.P., Antunes, I.C., Fernandes, M. da L., Phillips, M.R., 2014. Influence of mean sea level rise on Ria de Aveiro littoral: adaptation strategies for flooding events and shoreline retreat. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 320–325, ISSN 0749-0208. Floods and shoreline retreat in coastal areas threaten many millions of people across Europe. Moreover, it is agreed that climate change can amplify the magnitude and frequency of flooding events and accelerate the shoreline retreat. The main goal of this work is to assess flood and shoreline retreat risk, and define adaptation strategies under present conditions and future climate change scenarios on the Ria de Aveiro and its littoral. The hydrodynamic model ELCIRC was implemented for the Ria de Aveiro lagoon and GENESIS (U.S. Army Corps of Engineers) and LTC (Long-Term Configuration) shoreline evolution models for the littoral stretch between Esmoriz and Mira. Numerical results in present and future scenarios were used to map the flooded lagoon extension and the shoreline evolution of this coastal stretch. Analysis showed an increase of the lagoons flooded area, relative to the present, with regions more exposed to sea level rise being lowland areas located at the margins of the lagoons deeper channels. Examination of the littoral stretch showed a slight increasing trend of shoreline retreat under predicted future climate change scenarios, thereby increasing the probability of sand spit rupture. Data from numerical predictions were integrated into Geographical Information Systems covering the coastal and lagoon study areas, and produced hazard and risk maps including the identification of regional use and activities. Structural and non-structural measures were subsequently developed in order to mitigate flood and shoreline retreat effects.

Mapping erosion risk under different scenarios of climate change for Aveiro coast, Portugal

AbstractSeveral coastal zones are facing shoreline retreat problems, losing territory due to energetic sea actions, negative sediment transport balances and climate change phenomena. To deal with this problem, efficient tools are necessary to help decision-makers choose the right procedures to follow. These tools should assess, estimate and project scenarios of coastal evolution in a medium-to-long-term perspective. To perform reliable projections, as many variables as possible should be analysed, and the impact of each of these variables on the shoreline evolution should be understood. This study aimed to analyse three climate change phenomena that are considered the most important in a Portuguese west coast stretch (at Aveiro region). The considered phenomena are the wave height increasing due to storms, the wave direction changes and the sea level rise. A shoreline evolution numerical model, long-term configuration, developed to support coastal zone planning and management in relation to erosion problems was applied. This work defined a methodology for classification of risk areas, considering the uncertainty associated with different wave climate sequences on simulations. As a result, different risk maps according to considered climate change effects were obtained, defining areas of high, medium and low risk of territory loss due to erosion. A generalized erosion tendency and shoreline retreat were observed, particularly in the downdrift side of groins. The sea water level rise showed lower impacts in the shoreline evolution than wave direction changes, or wave height increasing, which presents the highest impact.

3D MOVABLE BED MODEL RESULTS INTEGRATION IN A SHORELINE EVOLUTION MODEL

The critical analysis of the performance of a medium to long-termshoreline evolution model, which incorporates bottom change updating based onpredefined rules, showed the need to improve processes description, namely beachprofile development under the action of different wave conditions. The absence ofcoherent field data sets, particularly expensive for high energetic coastal zones asis the case for the Portuguese west coast, together with the possibility to access anexperimental facility led to the completion of a three-dimensional movable bedmodel of a beach in a continued erosion situation. Furthermore, the effect of atransversal defense structure was also considered. The morphological time scaledetermination allowed the articulation between physical model results for profiledevelopment and simulations from the referred numerical model. Theinterpretation of these results, to what laboratory and scale effects were identified,may give some guidance for the numerical description of the profile development.

WAVE RUN-UP LIMITS: MAPPING MARITIME PUBLIC DOMAIN IN PORTUGAL

The maritime public domain in Portugal is defined for each place, by the line corresponding to the maximum high tide of equinoctial spring tides, depending on the waves run-up under average waves heights conditions. This approach has created challenges and problems to the responsible entities, which are not solved yet. The choice of a specific study area allows the definition of a suitable method to run-up evaluation, the perception of the difficulties in evaluating the LMPMAVE, and its application at the study site leading to definition of the effective boundary line in the field.