How did the AD 1755 tsunami impact on sand barriers across the southern coast of Portugal?

Tsunamis are highly energetic events that may destructively impact the coast. Resolving the degree of coastal resilience to tsunamis is extremely difficult and sometimes impossible. In part, our understanding is constrained by the limited number of contemporaneous examples and by the high dynamism of coastal systems. In fact, longterm changes of coastal systems can mask the evidence of past tsunamis, leaving us a short or incomplete sedimentary archive. Here, we present a multidisciplinary approach involving sedimentological, geomorphological and geophysical analyses and numerical modelling of the AD 1755 tsunami flood on a coastal segment located within the southern coast of Portugal. In particular, the work focuses on deciphering the impact of the tsunami waves over a coastal sand barrier enclosing two lowlands largely inundated by the tsunami flood. Erosional features documented by geophysical data were assigned to the AD 1755 eventwith support of sedimentological and age estimation results. Furthermore, these features allowed the calibration of the simulation settings to reconstruct the local conditions and establish the run-up range of the AD 1755 tsunami when it hit this coast (6– 8 m above mean sea level). Our work highlights the usefulness of erosional imprints preserved in the sediment record to interpret the impact of the extreme events on sand barriers

Tectonic and lithological controls on fluvial landscape development in central-eastern Portugal: Insights from long profile tributary stream analyses

This study examines the long profiles of tributaries of the Tagus and Zêzere rivers in Portugal (West Iberia) in order to provide new insights into patterns, timing, and controls on drainage development during the Quaternary incision stage. The studied streams are incised into a relict culminant fluvial surface, abandoned at the beginning of the incision stage. The streams flow through a landscape with bedrock variations in lithology (mainly granites and metasediments) and faulted blocks with distinct uplift rates. The long profiles of the analyzed streams record an older transitory knickpoint/knickzone separating (1) an upstream relict graded profile, with lower steepness and higher concavity, that reflects a long period of quasi-equilibrium conditions reached after the beginning of the incision stage, and (2) a downstream rejuvenated long profile, with steeper gradient and lower concavity, particularly for the final reach, which is often convex. The rejuvenated reaches testify to the upstream propagation of several incision waves, interpreted as the response of each stream to increasing crustal uplift and prolonged periods of base-level lowering by the trunk drainages, coeval with low sea level conditions. The morphological configurations of the long profiles enabled spatial and relative temporal patterns of incisions to be quantified. The incision values of streams flowing on the Portuguese Central Range (PCR; ca. 380–150 m) are variable but generally higher than the incision values of streams flowing on the adjacent South Portugal Planation Surface (SPPS; ca. 220–110 m), corroborating differential uplift of the PCR relative to the SPPS. Owing to the fact that the relict graded profiles can be correlated with the Tagus River T1 terrace (1.1–0.9 My) present in the study area, incision rates can be estimated (1) for the streams located in the PCR, 0.38–0.15 m/ky and (2) for the streams flowing on the SPPS, 0.22–0.12 m/ky. The differential uplift inferred in the study area supports the neotectonic activity of the bordering faults, as proposed in previous studies based upon other geological evidence.

CARACTERIZACIÓN GEOMORFOLÓGICA, AMENAZAS NATURALES Y RESTRICCIONES DE USO DE LA TIERRA EN ESPARZA, COSTA RICA: UN ENFOQUE DE ORDENAMIENTO TERRITORIAL PARA EL PLAN REGULADOR DEL CANTÓN

Resumen: Este artículo constituye parte del diagnóstico físico-ambiental que se redactó como uno de  los componentes del Plan Regulador de Esparza.   Mediante el acopio de informes  técnicos, mapas  temáticos,  fotos  aéreas  y  trabajo de  campo,  se  caracteriza,geológica  y  geomorfológicamente  el  sector.    En  este  último  apartado  se  identifican veintiséis geoformas   que   son objeto de un cuidadoso análisis para identificar no solo los  tipos de amenazas naturales que hacen vulnerable cada uno de esos territorios, sino que se formulan restricciones de uso y propuestas de uso apropiado.  Abstract: This article  is a part of a physic environmental diagnosis that was composed as  a  section  of  Esparza  Urban  Planning.  In  order  to  characterize  geological  and geomorphological aspects,  it  was  necessary  to  use  technical  reports, thematic  maps, aerial photographs and  fieldwork. As a part of a geomorphologic  research we  identify twenty six landforms. Each one of them has not only a technical name but also a kind of natural  hazard.  At  the  same  time  we  analyze  their  vulnerability  and  propose  use restrictions and made recommendations  about their suitability. 

PROPUESTA DE ZONIFICACIÓN TURÍSTICA COMO MODELO DE PLANIFICACIÓN TERRITORIAL PARA COMUNIDADES DEL GOLFO DE NICOYA

El proyecto “Diseño de productos y rutas turísticas alternativas para el mejoramiento del nivel de vida de las comunidades locales: el caso del Golfo de Nicoya” tiene como propósitos: la elaboración de un diagnóstico del sistema turístico de las comunidades involucradas, la evaluación del potencial turístico de los recursos y atractivos identificados en las comunidades, el diseño de productos y rutas turísticas, y la realización de una zonificación turística en las áreas de estudio. El presente artículo se centra en la zonificación turística de las comunidades metas, debido a que las variables anteriormente mencionadas son la base para su elaboración. La zonificación toma en cuenta los aspectos que condicionan los procesos de transformación y articulación del turismo en el territorio, desde el papel de los recursos naturales para la implantación turística y la influencia de la estructura territorial y socioeconómica sobre la que se organiza el turismo. Esta permite un mejor análisis del espacio geográfico y diseño de propuestas de desarrollo. En este caso, se identifican elementos homogeneizadores del espacio turístico a partir del diagnóstico de las comunidades, entre ellos se encuentran: la geomorfología, uso del suelo, tipología de recurso y atractivo turístico, la oferta y la demanda turística, entre otros. ABSTRACT The purpose of the project, “Design of Products and Tourist Route Alternatives for Improving the Standard of Living of Local Communities: The Case of the Gulf of Nicoya”, is to diagnose the system of tourism in the communities involved, evaluate the tourist potential of the resources and attractions of the communities, design products and tour routes, and establish tourist zones in the areas of study. This article focuses on the community goals of the tourist zones since the above-mentioned variables are the basis for their development. The zoning takes into account the aspects that condition the process of transforming an area into a tourist zone, from the role natural resources play in establishing tourism to the influence of socioeconomic and territorial structures. This allows a better analysis of the geographic space and design of development proposals. In this case, homogenous elements of the tourist space are identified from diagnosis of the communities, including the geomorphology, land use, typology of resource and tourist attractions, tourist supply and demand and other factors.

Mappatura degli habitat bentonici dei canali di marea della Laguna di Venezia tramite strumenti acustici e tecniche di ground-truth

The Venice Lagoon is a complex, heterogeneous and highly dynamic system, subject to anthropogenic and natural pressures that deeply affect the functioning of this ecosystem. Thanks to the development of acoustic technologies, it is possible to obtain maps with a high resolution that describe the characteristics of the seabed. With this aim, a high resolution Multibeam Echosounder (MBES) bathymetry and backscatter survey was carried out in 2021 within the project Research Programme Venezia 2021. Ground-truthing samples were collected in 24 sampling sites to characterize the seafloor and validate the maps produced with the MBES acoustic data. Ground-truthing included the collection of sediment samples for particle size analysis and video footage of the seabed to describe the biological component. The backscatter data was analysed using the unsupervised Jenks classification. We created a map of the habitats integrating morphological, granulometric and biological data in a GIS environment. The results obtained in this study were compared to those collected in 2015 as part of the National Flagship Project RITMARE. Through the comparison of the repeated morpho-bathymetric surveys over time we highlighted the changes of the seafloor geomorphology, sediment, and habitat distribution. We observed different type of habitats and the presence of areas characterized by erosive processes and others in which deposition occurred. These effects led to changes in the benthic communities and in the type of sediment. The combination of the MBES surveys, the ground truth data and the GIS methodology, permitted to construct high-resolution maps of the seafloor and proved to be effective implement for monitoring an extremely dynamic area. This work can contribute not only to broaden the knowledge of transitional environments, but also to their monitor and protection.