Coastal erosion in sandy beaches along a tectonically active coast: The Chile study case

Coastal erosion in 45 sandy beaches covering nearly 2000 km along the tectonically active Chilean coast is assessed during the last four decades. The historical analysis is based on the assessment of decadal changes of the shoreline position extracted from topographic surveys, aerial photographs, satellite images and survey maps using the DSAS software. Results show that 80% of the sites presented erosion rates (>−0.2 m/y), 7% beaches accreted (>0.2 m/y) while 13% remained stable. Eroded beaches include headland bay beaches, embayed and pocket beaches. A discussion on the possible causes explaining these results is conducted. While changes in offshore wave climate are spatially smooth within the region, relative mean sea level changes are highly variable and modulated by tectonic activity; the reduction of the sediment supply explains erosion rates in few cases.

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Landslide Erosion Rate in the Eastern Cordillera of Northern Bolivia

Earth Interactions ◽

10.1175/2007ei222.1 ◽

2007 ◽

Vol 11 (19) ◽

pp. 1-30 ◽

Cited By ~ 22

Author(s):

Troy A. Blodgett ◽

Bryan L. Isacks

Keyword(s):

Erosion Rate ◽

Aerial Photographs ◽

Field Surveys ◽

Bedrock Rivers ◽

Eastern Cordillera ◽

Erosion Rates ◽

Landslide Volume ◽

Tectonically Active ◽

Dominant Process ◽

Very High

Abstract The northeastern edge of the Bolivian Eastern Cordillera is an example of a tectonically active plateau margin where orographically enhanced precipitation facilitates very high rates of erosion. The topography of the steepest part of the margin exhibits the classic signature of high erosion rates consisting of high-relief V-shaped valleys where landsliding is the dominant process of hillslope erosion and bedrock rivers are incising into the landscape. The authors mapped landslide scars on multitemporal aerial photographs to estimate hillslope erosion rates. Field surveys of landslide scars are used to calibrate a landslide volume versus area relationship. The mapped area of landsliding, in combination with an estimate of the time for landslide scars to revegetate, leads to an erosion rate estimate. The estimated revegetation time, 10–35 yr, is based on analysis of multitemporal aerial photographs and tree rings. About 4%–6% of two watersheds in the region considered were affected by landslides over the last 10–35 yr. This result implies an erosion rate of 9 ± 5 mm yr−1 assuming that 90% of a single landslide reaches the river on average. Classified Landsat Thematic Mapper images show that landslides are occurring at approximately the same rate all across an approximately 40-km-wide swath within the high-relief zones of the cordillera.

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MIOCENE SCLERACTINIAN CORALS OF GAVDOS ISLAND, SOUTHERN GREECE: IMPLICATIONS FOR TECTONIC CONTROL AND SEA-LEVEL CHANGES

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11224 ◽

2017 ◽

Vol 43 (2) ◽

pp. 620

Author(s):

H. Drinia ◽

F. Pomoni-Papaioannou ◽

Tsaparas N. ◽

A. Antonarakou

Keyword(s):

Sea Level ◽

Eastern Mediterranean ◽

High Energy ◽

Tectonic Activity ◽

Sea Level Changes ◽

Reef Facies ◽

Reef Development ◽

Patch Reefs ◽

Tectonically Active ◽

Global Sea Level

Low-diversity scleractinian patch reefs that have been developed, during Early to Middle Tortonian, in Gavdos island are studied, aiming in a better understanding of the time and space relationships of the reef development and the associated basin fill evolution. Gavdos island consists part of a tectonically active setting constituting the southernmost extension of the Hellenic arc (Eastern Mediterranean). A representative Tortonian section (Bo section), located in the northwest part of the island, which hosts a mass occurrence of hermatypic corals, is studied. Scleractinian samples were collected from the upper 12 m of the section, which is characterized by interchanges of marly limestone and compact marls. The reefs are represented by the coral species Heliastraea oligophylla, Porites maicientensis, Thegioastraea roasendai and Porites collegniana. The microfacies analysis showed that the mediumto-thin-bedded carbonates of the limestone-marl alternations comprise patch reefs (boundstones-framestones, SMF 16, sensu Wilson, 1975, FZ 7-8, sensu Flügel 1982) consisted of screractinian corals. Corals are associated with corallinacean algae. Patch reefs are associated by bioclastic packstones-floatstones, characterized by benthic foraminifera, calcareous algae, spines of echinoids, gastropods and molluscs. Reefs are laterally associated by a bioclastic limestone rich in planktonic forams, associated by detrital material (fragments of quartz, feldspars, quartzites and cherts). The studied reef facies have been dolomitized and cemented in the meteoric realm. In places pseudomorphs after evaporites have been observed, tending to occlude cavities resulted after dissolution. The depositional environment corresponds to a moderate to high-energy inner platform setting, experiencing open-ocean influences. The pattern of coralgal reef development during Miocene, in the tectonically controlled Gavdos island, represents a complex interaction of tectonic activity and global sea-level changes.

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Morphology of the Raised Shore Platforms along the Coastline between Daghmar and Dhabab, Sultanate of Oman

Journal of Arts and Social Sciences [JASS] ◽

10.24200/jass.vol8iss2pp13-24 ◽

2017 ◽

Vol 8 (2) ◽

pp. 13 ◽

Cited By ~ 2

Author(s):

Salim Mubarak Al Hatrushi

Keyword(s):

Sea Level ◽

Late Quaternary ◽

Aerial Photographs ◽

Tectonic Activity ◽

Present Level ◽

Sea Level Changes ◽

Last Interglacial ◽

Southeastern Part ◽

Relative Level ◽

Shore Platforms

Raised shore platforms, are rocky surfaces formed by wave action and subaerial weathering during global high sea level stands. The present height of the raised shore platforms is attributed to several factors, mainly to eustatic sea level changes, isostatic changes in the relative level of land and sea, and vertical tectonic activities. The aim of this study is to investigate the detailed morphology of the raised shore platform along the rocky coastline between Daghmar and Dhabab, in the southeastern part of Muscat Governorate. The study also intends to establish a tentative chronology of the raised shore platforms development. The methodology is based on field observation and documentation, along with satellite and aerial photographs analysis. The results have shown that the study area has a sequence of five successive, well developed raised shore platforms and well preserved, except the platform at 10m altitude which is only found in isolated fragments. The formation of the raised shore platforms has been affected by a number of constructive factors including tectonic activity, and destructive factors such as fluvial action and subaerial weathering. No absolute dating has been reported or can be obtained from the study area, due to its erosional nature. However, dating from the shorelines adjacent to the study area, ranging in heights from 3 to 15m above sea level, revealed a narrow range of 26,400 to 29,600 years. This period coincides with the last glaciations when the sea level was at about 75m below the present level, and thus did not match with the altitudes of the platforms. This suggests that the platforms could be belong to the last interglacial high sea level, when the sea level stood at about 6m above the present level. Based on this scenario, the study concludes that the coastline of the study area has not experienced any significant uplift during the Late Quaternary.

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LONG TERM BEACH EROSION: MORPHODYNAMIC CASE STUDY IN MONT-ROIG BEACH, SPAIN

Coastal Engineering Proceedings ◽

10.9753/icce.v33.sediment.68 ◽

2012 ◽

Vol 1 (33) ◽

pp. 68

Author(s):

Jordi Galofré ◽

Dolores Ortiz ◽

Raúl Medina

Keyword(s):

Coastal Erosion ◽

Numerical Models ◽

Anthropogenic Impacts ◽

Wave Climate ◽

Sediment Supply ◽

Beach Erosion ◽

Classical Analysis ◽

Morphological Aspects

Long term coastal erosion in beaches induced by long-shore sediment transport is an important aspect to be taken account in beach behavior. If anthropogenic impacts in coastal stretch (harbor, detached breakwaters, lack of sediments from streams and gullies, and urban pressure) interrupting long-shore currents and transport and decreasing sediment supply, the coastal equilibrium disappears. In this paper a case study is shown in order to analyze long term beach behavior in a coastal stretch affected by erosion. After a brief description of morphological aspects, causes and effects that have incidence on the case study area will be shown. General background and coastal works are detailed. The ideas based on a classical analysis of beach behavior are exposed and results obtained from bathymetric analysis and numerical models are showed. Morphology, wave climate, morphodynamics and sediment budget are evaluated and morphodynamic beach behavior is proposed. A diagnosis is made and mitigation proposal for coastal erosion will be proposed.

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Critical beaches due to coastal erosion in the Caribbean south of Costa Rica, during the period 2005-2016

Revista Geográfica de América Central ◽

10.15359/rgac.64-1.5 ◽

2019 ◽

Vol 1 (64) ◽

pp. 123-150

Author(s):

Gustavo Barrantes-Castillo ◽

Isabel Arozarena-Llopis ◽

Luis Sandoval-Murillo ◽

José Francisco Valverde-Calderón

Keyword(s):

High Resolution ◽

Coastal Erosion ◽

National Park ◽

Sandy Beaches ◽

Costa Rican ◽

Aerial Photographs ◽

Shoreline Retreat ◽

The Caribbean ◽

High Resolution Satellite Imagery ◽

Erosion Hotspots

Since 2010, the local press has been reporting an accelerated process of erosion on the sandy beaches of the Costa Rican Caribbean coast, it has even been documented within protected areas. To quantify this process and identify coastal erosion hotspots in the Caribbean south, a methodology was proposed for detecting and delineating the shoreline using aerial photographs and high-resolution satellite imagery to determine the rate of shoreline retreat, the employed photographs and images cover the period between 2005 and 2016. By such means it was possible to identify eleven erosion hotspots, as well as estimation of their retreat rates for the periods 2005-2010 and 2010-2016. The localities that have experienced the greatest erosion of their sandy beaches are Cahuita National Park, Westfalia and Bananito Beach.

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Lifecycle of an Intermontane Plio-Pleistocene Fluvial Valley of the Northern Apennines: From Marine-Driven Incision to Tectonic Segmentation and Infill

Geosciences ◽

10.3390/geosciences11030141 ◽

2021 ◽

Vol 11 (3) ◽

pp. 141

Author(s):

Massimiliano Ghinassi ◽

Mauro Aldinucci ◽

Valeria Bianchi ◽

Andrea Brogi ◽

Enrico Capezzuoli ◽

...

Keyword(s):

Sea Level ◽

Drainage System ◽

Northern Apennines ◽

Sediment Supply ◽

Tectonic Activity ◽

Sea Level Changes ◽

Relative Sea Level ◽

Sedimentary Evolution ◽

Fluvial Sedimentation ◽

Forced Regression

Downcutting and infill of incised valley systems is mostly controlled by relative sea-level changes, and studies on valley-fill successions accumulated independently from relative sea-level or lake-level oscillations are limited. This study focuses on the Plio-Pleistocene evolution of a fluvial drainage system developed in Southern Tuscany (Italy) following a regional marine forced regression at the end of Piacentian. Subsequent in-valley aggradation was not influenced by any relative sea-level rise, and valley morphological and depositional history mainly resulted from interaction between sediment supply and tectonic activity, which caused segmentation of the major valley trunk into localized subsiding depocenters separated by upwarping blocks. Fluvial sedimentation occurred until late Calabrian time, when the major river abandoned that valley, where minor fluvio-lacustrine depocenters allowed accumulation of siliciclastic and carbonate deposits. The present study demonstrates that the infill of the valley was not controlled by the forcing that caused its incision. Accumulation of the fluvial succession is discussed here in relation with localized, tectonic-controlled base levels, which commonly prevent from establishing of a clear downdip stratigraphic correlations. Chronological reconstruction of the study depositional dynamics provides solid constrains to frame them in the tectono-sedimentary evolution of the Northern Apennines.

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Morphotectonic Analysis of Tanjung Bungo Area Based on Geological Structure Control, Central Sumatera Basin

Proc. Indon. Petrol. Assoc., Digital Technical Conference, 2020 ◽

10.29118/ipa20-sg-254 ◽

2020 ◽

Author(s):

D., A., L., A. Putri

Keyword(s):

Natural Resources ◽

River Flow ◽

Measurement Data ◽

River System ◽

Flow Patterns ◽

Source Rocks ◽

Aerial Photographs ◽

Morphological Data ◽

Tectonic Activity ◽

Geological Structures

Tectonic activity in an area could result in various impacts such as changes in elevation, level of slope percentages, river flow patterns and systems, and the formation of geological structures both locally and regionally, which will form a new landscape. The tectonic activity also affects the stratigraphic sequences of the area. Therefore, it is necessary to study morphotectonic or landscape forms that are influenced by active tectonic activities, both those occur recently and in the past. These geological results help provide information of the potential of natural resources in and around Tanjung Bungo area. Morphological data are based on three main aspects including morphogenesis, morphometry, and morphography. The data are collected in two ways, the first is field survey by directly observing and taking field data such as measuring geological structures, rock positions, and outcrop profiles. The second way is to interpret them through Digital Elevation Model (DEM) and aerial photographs by analyzing river flow patterns and lineament analysis. The field measurement data are processed using WinTensor, Dips, and SedLog Software. The supporting data such as Topographic Maps, Morphological Elevation Maps, Slope Maps, Flow Pattern Maps, and Lineament Maps are based on DEM data and are processed using ArcGis Software 10.6.1 and PCI Geomatica. Morphotectonically, the Tanjung Bungo area is at a moderate to high-class level of tectonic activity taken place actively resulted in several joints, faults, and folds. The formation of geological structures has affected the morphological conditions of the area as seen from the development of steep slopes, structural flow patterns such as radial, rectangular, and dendritic, as well as illustrated by rough surface relief in Tanjung Bungo area. This area has the potential for oil and gas resources as indicated by the Telisa Formation, consisting of calcareous silts rich in planktonic and benthonic fossils, which may be source rocks and its contact with the Menggala Formation which is braided river system deposits that could be good reservoirs. Further research needs to be done since current research is only an interpretation of surface data. Current natural resources being exploited in Tanjung Bungo region are coals. The coals have thicknesses of 5-7 cm and are classified as bituminous coals.

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