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

Guadiana estuary: present state, past evolution and prospects for the future

The Guadiana catchment extends over an area of 66 889 km2, between the catchments of the Tagus and Guadalquivir rivers, of which 11 525 km2 are in Portugal. Its upper part in Spain corresponds to what is called the Western La Mancha province. To the North the watershed is limited by alignments, of the Sierra de Altomira http://www.castillalamancha.es/sites/default/files/documentos/paginas/archivos/altomira_liczepa_fich.pdf ) with heights between 700 and 1,000 meters and the Mancha de Toledo, with profusion of endorheic lagoons between 600 and 800 meters above sea level. The origin of the Guadiana was historically placed in the area of Campo de Montiel under the name Rio Pinilla.info:eu-repo/semantics/publishedVersio

Inner shelf paleoenvironmental evolution as a function of land-ocean interactions in the vicinity of the Guadiana River, SW Iberia

This study investigates the land–ocean interactions along the northern margin of the Gulf of Cadiz in the vicinity of the Guadiana River. Benthic foraminifera and sedimentological characteristics were analysed in a sedimentary sequence spanning ca. 5000 years (core 8, 22 m water depth) retrieved from the inner shelf prodeltaic wedge. The analyses were integrated in a temporal framework based on accelerated mass spectrometry radiocarbon dating. Paleoenvironmental changes and sediment transfer mechanisms from the continent to the shelf were investigated and related to climatic oscillations and anthropogenic impact in the region. The results allowed the identification of two main periods of deposition. The first period, from ca. 5150 cal. BP (core base) to 1500–1200 cal. BP, is characterised by a mix of fine and coarse sediments, relatively constant percentages of terrigenous and bioclasts, and benthic foraminifera species characteristic of coastal environments. These features indicate an environment strongly influenced by discharge from the Guadiana River. The second period, from ca. 1500–1200 cal. BP to ca. 200 cal. BP (core top), is characterised by silt-clay fraction dominated sediments, an increase in terrigenous sediment towards the top, and benthic foraminifera species characteristic of environments with low levels of energy. An increase in the level of human occupation associated with changes in climate led to widespread erosion and soil loss to the continental shelf during this period, with possible silting up of the Guadiana eastern distributary, allowing the transport of high amounts of sediment to the shelf by the western distributary that led to the enhancement of fine sedimentation and the formation of the prodeltaic wedge in the area of the studied core

The impact of man on the morphodynamics of the Huelva coast (SW Spain)

The Huelva coast is composed by large sandy beaches and spits, only interrupted by the presence of the estuarine mouths of the Guadiana, Piedras, Tinto-Odiel and Guadalquivir which are in an advanced state of sediment infilling. The morphology and processes of the Huelva coast are mainly linked to tidal regime, wave action, coastal-drift currents, fluvial dynamics, climatic change and anthropogenic activity. In the last five decades anthropogenic activity has modified the natural dynamics by the construction of jetties, docks, harbour and coastal developments. The main consequences have been the interruption of the sedimentary bypassing caused by an active west-to-east littoral drift, the modification of the tidal regime, the wave refraction-diffraction scheme and the intensification of the littoral erosive processes. All these effects will increase with the slow sea-level rise, close to 0.6 cm per year, which will induce a higher efficacy of the erosional events. A future retreat of about 10-15 m of the coastline is estimated.La costa de Huelva esta constituida por extensas playas y flechas litorales, interrumpidas por la presencia de grandes estuarios (Guadiana, Piedras, Tinto-Odiel y Guadalquivir) en un estado avanzado de colmatación. La morfología y los procesos de la costa se deben principalmente a una serie de factores: régimen mareal, olas, corrientes de deriva, dinámica fluvial, cambio climático y la actividad antrópica. En las últimas cinco décadas la actividad antrópica ha modificado la dinámica natural debido a la construcción de espigones, escolleras, puertos y urbanizaciones. Las principales consecuencias de esta actividad han sido la interrupción del trasvase de sedimentos del Este hacia el Oeste por la corriente de deriva litoral, la alteración del régimen mareal, la modificación de los procesos de refracción-difracción de olas y la intensificación de los procesos erosivos. Todos estos efectos se verán incrementados con el paulatino ascenso del nivel del mar en el Golfo de Cádiz, del orden de 0,6 cm anuales, repercutiendo en una mayor eficacia de los eventos erosivos. Se estima una pérdida del orden de 10-15 m en el perfil de las playas

Extreme wave events in the southeastern Iberia coast: Blocks and megablocks as an indicator of tsunamis or extreme storms

Whilst the SW coast of the Iberian Peninsula has a significant record of extreme wave events (EWE), mostly associated with tsunamis, the Mediterranean coast offers a smaller record of these events, although some historical tsunamis with limited impact have been cited on the coast. In general, these studies have been based on the geological record of detrital sequences of sands and silts. In this case, we have focused on the study of coastal deposits of blocks and megablocks in Cope, Murcia (SE of Iberian Peninsula). Here, blocks greater than 1 m and located up to 4 masl were generated by an EWE associated to either a tsunamis or great storm. An unmanned aerial vehicle (drone) has been utilized to perform aerial photogrammetry, which complemented terrestrial photogrammetry of higher resolution.This has been processed to develop a 3D model of the terrain and obtain the dimensional and spatial parameters of these blocks. Different models have been used to calculate potential tsunami wave heights and scale of storms capable of generating such deposits (Nott, 2003; Engel and May, 2012). The results confirm the process of generating force required to generate the block ridges at this site