Morphological response of the saltmarsh habitats of the Guadiana estuary due to flow regulation and sea-level rise

In the context of rapid sea-level rise in the 21st century, the reduction of fluvial sediment supply due to the regulation of river discharge represents a major challenge for the management of estuarine ecosystems. Therefore, the present study aims to assess the cumulative impacts of the reduction of river discharge and projected sea-level rise on the morphological evolution of the Guadiana estuary during the 21st century. The assessment was based on a set of analytical solutions to simplified equations of tidal wave propagation in shallow waters and empirical knowledge of the system. As methods applied to estimate environmental flows do not take into consideration the fluvial discharge required to maintain saltmarsh habitats and the impact of sea-level rise, simulations were carried out for ten cases in terms of base river flow and sea-level rise so as to understand their sensitivity on the deepening of saltmarsh platforms.Results suggest saltmarsh habitats may not be affected severely in response to lower limit scenarios of sea-level rise and sedimentation. A similar behaviour can be expected even due to the upper limit scenarios until 2050, but with a significant submergence afterwards. In the case of the upper limit scenarios under scrutiny, there was a net erosion of sediment from the estuary. Multiplications of amplitudes of the base flow function by factors 1.5, 2, and 5 result in reduction of the estimated net eroded sediment volume by 25, 40, and 80%, respectively, with respect to the net eroded volume for observed river discharge. The results also indicate that defining the minimum environmental flow as a percentage of dry season flow (as done presently) should be updated to include the full spectrum of natural flows, incorporating temporal variability to better anticipate scenarios of sea-level rise during this century. As permanent submergence of intertidal habitats can be significant after 2050, due to the projected 79 cm rise of sea-level by the year 2100, a multi-dimensional approach should be adopted to mitigate the consequences of sea-level rise and strong flow regulations on the ecosystem of the Guadiana Estuary. (C) 2016 Elsevier Ltd. All rights reserved

Coastal responses to sea-level rise on centennial to millennial time scales: development of hybrid model-based forecasting for the Guadiana Estuary

Tese de doutoramento, Ciências do Mar, da Terra e do Ambiente (Dinâmica Litoral), Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015In the context of hybrid approach, this study was focused on formalizing and application of a simple and idealized model using a set of theoretical framework based on rule-based morphological expressions. Main objectives were: (1) to simulate the sedimentary infilling of the Guadiana Estuary palaeovalley due to eustatic sea-level rise during the Holocene, against previous geomorphological and post-glacial palaeoenvironmental reconstructions based on facies interpretation and 14C dating; (2) to assess potential morphological impacts and risk of habitat shift by simulating the morphological evolution of the Guadiana estuary and its intertidal zone for the worst case of sea level rise and sedimentation scenarios predicted for the 21st century; (3) to assess the sensitivity of bed friction coefficient, power index of the current velocity in the erosion rate function, river discharge, and sea-level rise rate in determining the decadal scale morphological evolution in the Guadiana estuary; and (4) To understand the effect of dam construction along the Guadiana river on the estuarine morphology. According to the results, the long-term modelling of the morphological evolution in the estuary due to sea-level rise during the Holocene complemented previous reconstructions, based on interpretations of the experimental data. The intermediate hybrid approach that was followed in this study appears to be a useful tool for simulating the morphological evolution of an estuarine system during the period of postglacial sea-level rise. It seems particularly suited to the more sheltered environments of an estuarine system where vertical aggradation dominates the sedimentary infilling of the palaeovalley. However, the direct application of Estuarine Sedimentation Model and the intermediate hybrid model, are very much applicable to a system where there is net accretion throughout the estuarine system. These constraints were compensated to a certain extent using the fully developed hybrid model as it was able to produce elevation change distribution from 2000 to 2014 in the Guadiana estuary, approximately similar to the observed normal probability distribution for the same period. This improved model was able to produce spatial variability of eroding and accreting regions, enabling the coupling of decadal scale model to centennial scale model. Furthermore, results indicate the deficiencies of defining the environmental flow as a percentage of dry season flow and the risk of habitat loss from the intertidal zone. Thus, a multi-dimensional approach has to be adopted to mitigate their consequences of sea-level rise and drastic flow regulations on the ecosystem of the Guadiana estuary.No contexto de uma abordagem híbrida, este estudo focou-se na formalização e aplicação de um modelo simples e idealizado baseado no enquadramento teórico resultante de expressões geomorfológicas. Os objetivos principais foram: (1) simular o preenchimento sedimentar do palaeovale do estuário do Guadiana devido à subida eustática do nível do mar durante o Holocénico, considerando reconstruções geomorfológicas e pós-glaciais palaeoembientais por sua vez baseadas em interpretação de fácies e datações por Carbono-14; (2) avaliar os potenciais impactos morfológicos e de risco de mudança de habitats através da simulação fa evolução morfológica do estuário do Guadiana e respetiva zona intertidal de acordo com o pior cenário de subida do nível do mar e de sedimentação projetado para o século XXI; (3) avaliar a sensibilidade do coeficiente de fricção de fundo, índice de potência da velocidade de corrente na função de taxa de erosão, e taxa de subida de nível do mar na determinação da evolução morfológica do estuário do Guadiana numa escala temporal de décadas; e (4) perceber qual o efeito na morfologia estuarina da construção de barragens ao longo do rio Guadiana. De acordo com os resultados obtidos, a modelação a longo prazo da evolução morfológica do estuário devido â subida do nível do mar durante o Holocénico complementou reconstruções prévias baseadas em interpretações de dados experimentais. A abordagem intermédia híbrida seguida neste estudo apresenta-se como uma ferramenta útil para simulação da evolução morfológica de um sistema estuarino durante o período de subida do nível do mar pós-glacial. Torna-se ainda particularmente aplicável a ambientes mais abrigados de um sistema estuarino onde a agradação vertical domina o processo de preenchimento sedimentar do palaeovale. Porém, a aplicação direta do Modelo de Sedimentação Estuarina e do modelo intermédio híbrido é igualmente aplicável a um sistema onde exista acreção generalizada por todo o sistema estuarino. As limitações encontradas foram relativamente compensadas através da utilização do modelo hibrido totalmente desenvolvido. Este permitiu estimar a variação de elevação do estuário do Guadiana entre 2000 e 2014 de forma aproximadamente semelhante à distribuição normal de probabilidade observada para o mesmo período. Este modelo melhorado permitiu a produção de variabilidade espacial de regiões em acreção e erosão, possibilitando a união entre o modelo operante à escala de décadas com o modelo operante à escala de séculos. Ainda, os resultados obtidos apontam para as limitações na definição de um caudal ecológico como um percentagem do caudal em época seca, e o risco de perda de habitats da zona intertidal. Assim, uma abordagem multi-dimensional deverá ser adotada de forma a mitigar as consequências da subida do nível do mar e da regulação drástica do caudal no ecossistema do estuário do Guadiana.FCT - Fundação para a Ciência e Tecnologia: SFRH/BD/70747/201

Impact of shoreline retreat and inundation due to sea level rise along the coastline adjacent to the Guadiana estuary, Portugal/Spain border

Dissertação de mestrado, Gestão da Água e da Costa, Universidade do Algarve, 2008The integrated impact assessment of shoreline retreat and inundation due to sea level rise over the coastal zone of the Guadiana estuary, Portugal/Spain border was carried out to identify and map hazard zones. Geographical Information System tools were used to visualize and analyse impacts on built-up area, transportation network and habitats. The shoreline retreat with the present shoreline evolution rate and the accelerated sea level rise given by three SRES scenarios, namely, B1, A1B and A1FI (upper-bound values: 38, 48 and 59 cm rise in sea level, respectively) exhibit high spatial variability. The adjacent coastline of Monte Gordo tourist beach (Portugal) and the entire shoreline of Ayamonte municipality (Spain) are susceptible to severe erosion. The erosion extent increases gradually with the sea level rise. However, the main forcing of the shoreline retreat is not the climatic change but anthropogenic interventions including construction of coastal defense structures. The first order assessment of shoreline retreat for a hypothetical storm surge with elevated flood contours due to sea level rise shows that the damage to the built-up area and urban habitat can be long lasting while the sandy dune and salt marsh habitats may have resilience depending on sediment supply. The vulnerability of Portuguese side of the Guadiana estuary coastal zone for inundation due to storm surges of 3.0 and 4.9 m from mean sea level (1 and 2 m from the maximum spring high tide level, respectively) shows approximately two-fold and four-fold increase, respectively, relative to the hazard zone marked by the maximum spring high tide (1.9 m from MSL). Two- and three-fold respective increase can be seen in Spain side of the estuary. However, in terms of total area of inundation, Spanish side would severely affect. The main response should be focused on Integrated Coastal Zone Management programme with strategically planned soft engineering interventions to mitigate the negative impacts of shoreline retreat due to sea level rise hazards

Effects of sea level rise on salinity and tidal flooding patterns in the Guadiana Estuary

Sea level rise is a worldwide concern as a high percentage of the population accommodates coastal areas. The focus of this study is the impact of sea level rise in the Guadiana Estuary, an estuary in the Iberian Peninsula formed at the interface of the Guadiana River and the Gulf of Cadiz. Estuaries will be impacted by sea level rise as these transitional environments host highly diverse and complex marine ecosystems. The major consequences of sea level rise are the intrusion of salt from the sea into fresh water and an increase in flooding area. As the physical, chemical, and biological components of estuaries are sensitive to changes in salinity, the purpose of this study is to further evaluate salt intrusion in the Guadiana Estuary caused by sea level rise. Hydrodynamics of the Guadiana Estuary were simulated in a two-dimensional numerical model with the MOHID water modeling system. A previously developed hydrodynamic model was implemented to further examine changes in salinity distribution in the estuary in response to sea level rise. Varying tidal amplitudes, freshwater discharge from the Guadiana River and bathymetries of the estuary were incorporated in the model to fully evaluate the impacts of sea level rise on salinity distribution and flooding areas of the estuary. Results show an overall increase in salinity and land inundation in the estuary in response to sea level rise.info:eu-repo/semantics/publishedVersio

Fleur de sel composition and production: analysis and numerical simulation in an artisanal saltern

This study is a first approach to modelling of fleur de sel production, aimed at increasing its efficiency and contributing to the scarce literature on the topic. Quantitative forecasting of daily production of fleur de sel was applied to an artisanal solar pond unit in the environmentally protected area of Castro Marim, SE Portugal. The numerical model was based on simulations of the evaporation process, taking into account the effect of reduced vapour pressure of the brine solution. The controlling variables chosen as input parameters to the forecast model were brine temperature, brine concentration, harvesting efficiency, albedo, incoming solar radiation, precipitation, air relative humidity, air temperature, atmospheric pressure, day of the year, wind direction, and wind speed. Production predicted by the model was tested against actual production in two crystallisers in the years 2015 and 2017. The statistically evaluated match between the estimated and actual production was highly significant with a mean R-2 of 0.8 and overall error of estimation was 14.5%. The chemical composition of nine samples of fleur de sel was analysed, showing the temporal evolution of several components during the harvesting period. A decrease of NaCl content from 96% to 87% and an increase by one order of magnitude of Mg, S, K, Br, and As were observed. The range of Ca, Si, Al, and Sr contents was 0.12-0.65%, 0.1-0.85%, 0.08- 0.3%, and 0.009-0.013%, respectively. Ba, Fe, Mn, Mo, Pb, and Sn contents had the following ranges: 0.051-0.145, 1.2-5.5, 0.44-1.66, 0.03-0.05, <0.05-0.55, and <0.05-0.1 mg/kg, respectively. The following elements were below the detection limit and below the limits of the Codex Alimentarius: Cd, Th, U, Cu, Cr, Co, Ni, V, Bi, Zn, Rb, and Hg.Erasmusthorn (European Commission)Banco Santander IberoamericaUniversity of Cadizinfo:eu-repo/semantics/publishedVersio