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Initial evaluation of the use of RFID sensors for monitoring the geomorphological dynamics of a boulder beach. (Oia, Galicia)
Abstract and Figures
Recent technological advances have made it possible to improve the accuracy of coastal studies through devices such as RFID (Radio Frequency IDentification). These sensors allow the monitoring of elements of the
environment at any time since its placement and offer a great level of detail. This research is developed in a boulder beach in Oia (Pontevedra), where 80 RFID sensors were installed in the natural boulders, without changing their position. The sensors were placed in lines of 5 elements perpendicular to the coastline. After the first winter, there is a general movement of the boulders. Of the 48 recovered, 81% have displaced more than 50 cm, minimum value to consider that there was movement. The greater displacements have occurred in boulders whose axes didn’t exceed 100 cm, with a maximum distance of 20,47 meters. As for the areas of greater mobility, it is clearly perceived that the central sector of the study area present greater variations in the position of the boulders, while the north and the lower part of the beach, where it is located coastal platform, are the most stable areas.
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... A partir de estos resultados se introdujeron sensores RFID en el caso de Oia, este ha sido uno de los primeros usos de RFIDs en ambientes con acumulaciones de bloques, aunque previamente se habían empleado en plataformas costeras y sectores antrópicos (Bertoni et al., 2016;Hastewell et al., 2019). Con el análisis entre 2016 y 2019 se han identificado los principales patrones de movimiento en Oia con variaciones superiores a los 20 m y se han podido conocer en detalle los sectores más dinámicos (Gómez-Pazo et al., 2021b;Gómez-Pazo & Pérez-Alberti, 2017). ...
Resumen de la tesis doctoral de Alejandro Gómez Pazo, presentada en la Universidad de Santiago de Compostela con el título "Aplicación de novas tecnoloxías no estudo da costa de Galicia dirixidas a unha nova xestión no contexto do cambio global".
Publicado en la sección de tesis doctorales del Boletín de la Asociación de Geógrafos Españoles
... The relatively low cost of the transponders permits large numbers to be used to trace sediment movement over periods, due to long battery life, of up to several years (Johnson, 2010). Although most of the early applications of RFID transponders to address geomorphological problems was in fluvial environments (Nichols 2004;Liébault et al., 2012;Ravazzolo et al., 2014), they have been adopted to study a range of sediment transport issues in coastal environments (Allan et al., 2006;Benelli et al., 2011;Dickson et al., 2011;Chapuis et al., 2014;Casamayor et al., 2015;Bertoni et al., 2016;Gómez-Pazo and Pérez-Alberti, 2017;Hastewell et al., 2019Hastewell et al., , 2020. ...
Previous studies using unmanned aerial vehicles and remote sensing techniques have provided data on group sediment dynamics and overall mobility of a boulder beach at Oia in Galicia, northwestern Spain. They recorded changes in the location and disposition of hundreds of clasts but were unable to trace the intermittent movement of individual boulders. Radio Frequency IDentification (RFID) sensors were used in the present study to identify and record the long-term trajectories of boulders in this area. Sensors were installed in 80 boulders (mean intermediate axes approximately 55 cm) in September 2016 and were used to locate and record their displacement on five occasions, terminating in December 2019. Although burial and other factors prevented data being collected from every tagged boulder during these periods, recovery rates ranged from approximately 50%–75% of the original population. There was considerable variability in the displacement of the boulders, with maxima of >20 m and mean values >5 m. The distance of travel tended to decrease during the course of this study, despite a corresponding increase in storm frequency and intensity. Patterns of movement, including transport distance and direction were essentially chaotic in nature, reflecting the complex interaction and compound effect of a multitude of controls related to such factors as the location of boulders on the beach, their relationship to surrounding boulders, including the effects of sheltering, interlocking, and burial, and their size, shape, and other physical characteristics. The unpredictable behaviour and high transport thresholds of boulder beaches are in contrast to sand and gravel beaches that are characterized by more uniform and predictable patterns of sediment transport and morphological change.
... RFID (Radio-Frequency IDentification) sensors have recently been used to monitor the movements of boulders at Oia. Gómez-Pazo and Pérez-Alberti (2017) have reported that 81% of the boulders moved more than 50 cm in the winter of [2016][2017], with an average displacement of 5.06 m. These changes in position are associated with winter storms and the arrangement of the boulders on the beach. ...
The coastline of Galicia is more than 2100 km long (POL Galicia 2010) (Fig. 2.1). Two broad types of coast can be differentiated in the region: zones with rías and zones without rías. Marine inlets dominate in the former, whereas rectilinear stretches dominate in the latter and only small coves or estuaries occur. The megaforms of coastal relief in northwest Spain are clearly determined by the tectonic structure, whereas lithological differentiation has played a predominant role in the genesis of meso and microforms (Pérez-Alberti and Blanco-Chao 2005). In general, different factors are involved in shaping the coastline: the overall structure is determined by tectonic processes; the lithology causes differential erosional processes that define the broad features of the coastal front; and, finally, the succession of geomorphological processes that have taken place over time have determined the specific forms and distribution of the different environments. In addition, human activity has affected many areas, particularly the low-lying coastline.
The aim of this research is to deepen the knowledge of rocky coasts in general, and the Galician coasts in particular. This project carries out an analysis in different scales using the new technologies as the base to improve the coastal knowledge. Devices such as the Equotip are used at the microscale, in the mesoscale this project used RFID (Radio Frequency IDentification) sensors to analyze the displacements in boulder beaches, and lastly, UAV flights data are used in the macroscale to understand the behavior of different coastal typologies, as boulder beaches or cliff areas. Based on the obtained results and from the literature review, we proceed to analyze the risks associated with each type of coast, with particular emphasis in their vulnerability in the global change context. Thus, we developed the necessary recommendations for the existing risks, to improve the coastal management, reviewing the coastal management plans evolution and their possible future.
En este estudio se pretende clasificar distintas zonas del litoral gallego para así poder visualizar con claridad sus diferencias y analizar las razones que marcan los distintos paisajes. Para alcanzar este objetivo inicialmente se realizó un análisis cuantitativo en el que se han considerado la altitud del sector costero (6 categorías) y la rugosidad del terreno (4 categorías), calculando ambas variables con una resolución espacial de 2 metros. De este análisis se obtuvieron un total de 24 tipologías litorales. A partir de los tipos de costa generados se realizó un análisis interpretativo en el que se tuvieron en consideración las características paisajísticas de cada sector, como la litología o los usos de suelo presentes. Como resultado de este trabajo se han evidenciado las grandes diferencias existentes en el litoral gallego, desde zonas como la costa sur donde destacan las altitudes bajas con rugosidades elevadas hasta áreas como la costa lucense donde dominan las altitudes medias y rugosidades moderadas. La variedad de tipos de costa determina junto con la diversidad de usos del suelo la configuración de los distintos paisajes presentes en el litoral gallego, en el que se encuentran zonas muy diferenciadas en espacios muy próximos.
Recovery rates were obtained by radio frequency identification (RFID) technology in pebbles and cobbles at San Felipe beach, Gran Canaria. The aim of this work was to define which factors affected the recovery of tagged gravels. Several tests were performed to determine the detection depth threshold, and 16 field experiments were carried out over seventeen months after tracer deployment on the beach. Recovery rates are highly variable with time, ranging from 72.2% in the first recovery session to 25.8% in the last one. Nevertheless, a nearly stable situation was found for the final eight months. Apart from the effect of time, there were several factors that affected the recovery rate. Some of these were related to the particle, such as the position of the tag within the particle, as well as its weight, size and shape. Two environmental factors were considered. First, the elevation of the tracer on the beach showed that the recovery rate was higher with particles located above the storm berm. Second, wave height, which showed no relation with recovery rates even though during the experiment significant storms and periods of calm took place.
The Udden-Wentworth grain-size scale is widely used as the standard for objective description of sediment, but it inadequately covers gravel, the dominant fraction in many environments such as alluvial fans. The scale is most detailed in the sand and mud fractions, where grades such as "fine sand" are defined by particle intermediate axial length (</,). We propose similar detailed grades for gravel with dl boundaries consistently determined by extending the Udden-Wentworth scheme of multiples of 2 (whole increments). The 2 to 4 mm granule class (- 1 to -2 (f>) in this system consists of just one grade, but the pebble class comprises four: fine pebbles with </, from 4 to 8 mm (-2 to -3 <£), medium pebbles from 8 to 16 mm (-3 to -4 <£>), coarse pebbles from 16 to 32 mm (-4 to -5 ), and very coarse pebbles from 32 to 64 mm (-5 to -6 cb). Coarser grades are/we cobbles with di from 6.4 to 12.8 cm (-6 to -7 tb), coarse cobbles from 12.8 to 25.6 cm (-7 to -8 tb),fine boulders from 25.6 to 51.2 cm (-8 to -9 <£), medium boulders from 51.2 to 102.4 cm (-9 to -10 </)> coarse boulders from 102.4 to 204.8 cm (-10 to -11 </>), and very coarse boulders from 204.8 to 409.6 cm (-11 to -12 tb). These terms can be used in Folk's texture classification to derive detailed descriptions such as "angular, poorly sorted, fine to coarse boulder conglomerate". This grain-size scheme is further extended to account for particles coarser than boulders (rf, > 4.1 m), which we collectively call megaclasts, and the sediment they comprise megagravel or, if lithified, megaconglomerate, Megagravel is divided into four classes based on </ including blocks from 4.1 to 65.5 m (-12 to -16 (b), slabs from 65.5 to 1049 m (-16 to -20 $), monoliths from 1 to 33.6 km (-20 to -25 0), and megaliths from 33.6 to 1075 km (-25 to -30 <b). The first three classes cover the coarsest sediment currently known. Their grades are fine blocks, with dt from 4.1 to 8.2 m (-12 to -13 $), medium blocks from 8.2 to 16.4 m (-13 to -14 <b), coarse blocks from 16.4 to 32.8 m (-14 to -15 tb), very coarse blocks from 32.8 to 65.5 m (-15 to -16 (}>),fine slabs from 65.5 to 131 m (-16 to -17 ), medium slabs from 131 to 262 m (-17 to -18 tf>), coarse slabs from 262 to 524 m (-18 to -19 tb), very coarse slabs from 524 to 1049 m (-19 to -20 ), very fine monoliths from 1.0 to 2.1 km (-20 to -21 4>),fine monoliths from 2.1 to 4.2 km (-21 to -22 tb), medium monoliths from 4.2 to 8.4 km (-22 to -23 tb), coarse monoliths from 8.4 to 16.8 km (-23 to -24 tb), and very coarse monoliths from 16.8 to 33.6 km (-24 to -25 tb). These grades also can be used in Folk's texture classification for objective sediment description. We reserve the megalith class and five attendant grades for even coarser megaclasts, with dl spanning from 33.6 to 1075.2 km (-25 to -30 tb).
Abrasion is one of the less known processes operating on rocky coasts. This work tries to show some of the basic mechanisms in this type of processes, namely in coarse-grained beaches. The two main factors in the abrasive processes are the balance wave energy and clast size, but in areas in which the existence of thick periglacial and fluvio-nival continental deposits are common, other factors operating at medium time scales are also very important. The morphology of the rocky platforms and the Holocene erosion of cliffs shaped on heterometric deposits developed during the last marine regression, are strongly related.
In this paper the abrasion rate on a coarse-clastic beach was evaluated by calculating the volume loss recorded on indigenous pebbles within a 13-month timespan. The experiment was carried out at Marina di Pisa (Italy) on an artificial beach that was built to counteract the erosion processes affecting this sector of the coast. A total of 240 marble pebbles (120 rounded and 120 angular) were marked using the RFID technology and injected on the beach. The volume loss measured after consecutive recovery campaigns was progressively increasing, reaching the maximum value after 13 months (61% overall). The average volume loss is consistent between rounded and angular pebbles at any time (59.3% and 64.2% after 13 months respectively), meaning that the roundness is not a primary control factor on abrasion rate. The pebbles that did not reach such abrasion rates after 8 and 10 months (volume loss less than 20%) were found at heights equal or greater than 2 m above mean sea level, on the crest of the storm berm that formed during the strongest storms. This implies that the highest wearing is achieved in the lower portion of the backshore, which is also the area that underwent major topo-graphic modifications. Here, sea water action might also exert chemical influence on the pebbles, adding to the mechanical abrasion. The main result of this research, indicating an impressive volume loss on beach pebbles in a short timespan, could be of key importance for coastal managers. The optimization of coarse sediment beach nourishments is also relevant , taking into right consideration that the volume loss due to sediment abrasion might exceed 50% of the original fill volume just after 1 year in the most dynamic portion of the beach.
Low altitude flights by a micro-drone were made in 2012 and 2013 over two boulder beaches in northwestern Spain. Geographical information system software was used to map the data. Boulder outlines from the first flight were recorded on 4796 clasts at Laxe Brava and 2508 clasts at Oia. Changes in location were identified by overlaying these outlines on the 2013 images. About 17.5 % of the boulders (mean surface area 0.32 m2) moved at Laxe Brava and about 53 % (mean surface area 0.23 m2) at Oia. Most movement on both beaches was between the mid-tide to about 2 m above the high tidal level. The location and elevation of the highest points were also recorded on the 2012 images on 4093 boulders at Laxe Brava and 3324 boulders at Oia. These elevations were compared with the elevations at the same locations in 2013. The occurrence and scale of the elevational changes were generally consistent with changes in the boulder outlines. The study confirmed that boulder beaches can be cheaply and effectively monitored using high resolution, micro-drone technology. This article is protected by copyright. All rights reserved.
Coastal Geomorphology, Second Edition is a comprehensive and systematic introduction to this subject and demonstrates the dynamic nature of coastal landforms, providing a background for analytical planning and management strategies in coastal areas that are subject to continuing changes. This introductory textbook has been completely revised and updated, and is accompanied by a website which provides additional illustrations, global examples, case-studies and more detailed and advanced information on topics referenced in the book, together with explanations of terminology, annotated references and research material.
The Schmidt Rock Test Hammer was used to study the effect of abrasion on shore platforms in Galicia, northwestern Spain. On platforms where tidally-induced weathering (salt, wetting and drying, etc.) is dominant, rock strength is significantly lower than in areas where abrasion is, or has been active in the recent past. This suggests that abrasion removes weathered surface material, exposing the stronger, less weathered rock below. Abrasion downwearing, measured with a transverse micro-erosion meter, ranged between 0.13 and 1.8 mm yr− 1 over the last year. Most active abrasion occurs in the upper part of the intertidal zone, but weathering is slowly destroying formerly abraded surfaces at lower elevations. These abandoned surfaces were abraded by materials supplied by erosion of fluvio-nival and periglacial slope deposits that covered, or partially covered, parts of the Galician coast during the middle and late Weichselian. During the Holocene, rising sea level and erosion of the slope deposits caused the abrasion zone to gradually migrate up to its present position near the high tidal level. The spatial and temporal role of abrasion on this coast is, therefore, closely associated with the exhumation and inheritance of ancient platform surfaces from beneath Weichselian deposits.
This paper is concerned with the effect of sediment accumulation on shore platform development. Boulder accumulations are common on the granitic shore platforms of Galicia, northwestern Spain. Boulders are produced by erosion of shore platforms and of cliffs consisting of cold-climate deposits from the last glacial period. Measurements were made of the long axis length of more than 800 boulders, and additionally of the short and intermediate axes of 340 of these boulders, as well as of their orientation and gradient. There were two study areas. The boulders on the Barbanza Peninsula are generally a little smaller than those in southern Galicia with, respectively; mean long axis lengths of 0.98 and 1.14, and masses of 1.06 and 1.59 t. There are also some isolated, very coarse boulders and megaclasts in southern Galicia. The distribution and extent of the deposits and boulder imbrication and orientation testify to the high levels of wave energy produced by northwesterly and westerly storms in this region. Although the boulders, as well as the underlying shore platforms, were inherited, in part, from previous interglacial stages, some boulder detachment and movement is occurring today during storms, when significant deep water wave heights exceed 8 to 10 m. Despite some abrasion of the shore platforms, the primary effect of large boulder accumulations is protective. The role of sediment on shore platforms has been neglected, but this study suggests that because of arrested development under thick accumulations, platform gradient in areas with abundant sediment increases with the grain size of the material. The occurrence and type of sediment on shore platforms may therefore help to explain the distribution of sloping and subhorizontal platforms under different morphogenic and geological conditions.
There have been considerable advances in rock coast research in the past decade, as measured in terms of the number of active researchers and in the number of research papers being produced. This review, although not exhaustive, highlights many of the improvements that have been made in our ability to identify and measure the processes shaping rock coasts, at a range of spatial and temporal scales. We review how researchers are experimenting with new techniques; grappling with quantifying the effects of multiple processes on resultant landforms; and exploring how well rock coast systems relate to wider geomorphological and earth science debates. Recent research, including those in this special issue, aptly demonstrate the scientific benefits that can be accrued by studying rock coasts at a variety of spatial and temporal scales, by considering the effect of the wide range of processes that operate on them, and by the application of new measurement techniques and approaches. Despite these advances, there is ample scope for future research, which could profit from increasing collaboration with other coastal geomorphologists and allied earth science disciplines in order to identify and quantify linkages between rock coasts and other coastal systems. It is also important that new research considers how rock coasts will respond to extreme events and to risks associated with changing climate, and to how rock coast geomorphology might contribute, beyond coastal science, to wider debates in theoretical geomorphology.