Examinando por Materia "geomorphology"
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Ítem Assessing the effect of sea-level change and human activities on a major delta on the Pacific coast of northern South America: The Patía River(ELSEVIER SCIENCE BV, 2012-05-15) Restrepo A, Juan D.; Universidad EAFIT. Departamento de Geología; Ciencias del MarThis paper presents the main physical and human-induced stresses that have shaped the recent evolution of the Patía River delta, the largest and best-developed delta on the western margin of South America. During the Holocene, the Patía Delta moved southward and the northern part became an estuarine system characterized by large extensions of mangrove ecosystems. However, a major human-induced water diversion, starting in 1972, diverted the Patía flow to the Sanguianga River, and shifted the active delta plain back to its former Holocene location. This discharge diversion has led to sediment starvation of the southern delta lobe and changed the northern estuarine system into an active delta plain. In addition, coastal areas of the Patía delta subsided as a result of a devastating tsunami in 1979. Morphological changes along the delta coast are evidenced by: (1) coastal retreat along the whole delta front during the period 1986-2001; (2) coastal retreat along the abandoned delta lobe for the period 2001-2008; 56% of the southern delta shoreline is retreating and only 4% of the coast shows signs of accretion; (3) progradation of the northern delta region during the period 2001-2008; the discharge diversion of the Patía River to the Sanquianga has apparently balanced the observed trends in coastal erosion and sea-level rise (5.1mmyr -1 for the period 1984-2006, after the 1979 tsunami); (4) formation of transgressive barrier islands with exposed peat soils in the surf zone; and (5) abandonment of former active distributaries in the southern delta plain with associated inlet closure. In the northern delta lobe, major geomorphic changes include: (1) distributary channel accretion by morphological processes such as sedimentation (also in crevasses), overbank flow, increasing width of levees, inter-distributary channel fill, and colonization of pioneer mangrove; (2) freshening conditions in the Sanguianga distributary channel, a hydrologic change that has shifted the upper estuarine region (salinity<1psu) downstream; and (3) changes in vegetation succession; approximately 30% of mangrove forests in the current delta apex have been replaced by freshwater vegetation. Overall, the recent evolution of the Patía has been controlled by the interplay of (1) high basin-wide sediment load; (2) low discharge variability (Q max/Q min); (3) spatial switch of delta distributaries related to tectonic movements and subsidence; (4) a relative sea-level rise of 5.1mmyr -1 after the occurrence of the 1979 tsunami; (5) episodes of sea-level rise associated with the ENSO cycle; and (6) human-induced discharge diversion. The information presented here is valuable evidence for understanding the role of extreme events versus 'normal' conditions in creating and shaping deltas. © 2012 Elsevier B.V.Ítem Expanding level of coastal armouring: Case studies from different countries(COASTAL EDUCATION & RESEARCH FOUNDATION, 2011-01-01) Stancheva, M.; Rangel-Buitrago, N.; Anfuso, G.; Palazov, A.; Stanchev, H.; Correa, I.; Universidad EAFIT. Departamento de Ingeniería; Ciencias del MarConcreting the natural shoreline by use of traditional hard protective structures, as well as by port/harbour developments is commonly known as coastal armouring. Over the recent decades the expanding level of coastline hardening and its adverse impacts on the environment has arisen as one of the most critical problems all over the world. Therefore, our goal in this study was to demonstrate the crucial issue of progressive extent of technogenous coastal occupation by two case studies from different countries in Europe and in South America: Bulgaria and Colombia. To assess direct impact of armouring on the coastline and adjacent areas two case areas were selected for detailed investigation: an 18 km long coastline of the large Varna Bay (Bulgarian Black Sea coast) and 349 km long littoral of the Cartagena municipality (Caribbean coastline of Colombia). An indicative coastal segmentation of the both case sites by geomorphologic and engineering criteria was first implemented in GIS environment. As well as, for quantitative assessment of the influence of all maritime structures (port and coast-protection) on the studied coasts the coefficient of technogenous impact K was explored. A GIS methodology was applied for data processing, mapping the natural landforms/structures and to evaluate the technogenous impact on the both coastlines. The identified high extent of impacts due to built hard defence structures along the selected study areas in Bulgaria and Colombia could be considered as indicative of the large technogenous occupation of the coasts and the increasing level of shoreline armouring as a global issue.Ítem Fission-track datings and geomorphic evidences for long-term stability in the Central Cordillera highlands, Colombia(Gebruder Borntraeger Verlagsbuchhandlung, 2006-01-01) Toro, G.; Hermelin, M.; Schwabe, E.; Posada, B.O.; Silva, D.; Poupeau, G.; Toro, G.; Hermelin, M.; Schwabe, E.; Posada, B.O.; Silva, D.; Poupeau, G.; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y TectónicaAge of weathered andesitic volcanic ash layers, which cover most of the landscape in the Central Cordillera northern massif plateaus in Colombia, were determined through the use of fission track counting in volcanic zircon crystals. A stoneline, exposed in many outcrops, which corresponds to the lower limit of younger tephras, gave ages between 350 ka and 440 ka. Andosols lying above the stoneline could not be dated. Paleolake deposits in the study area and surroundings were dated at about 2 Ma; older ashes deposited on the Rio Negro erosion surface (SII) below the stoneline level gave ages between 3.4 and 5.4 Ma. The study area is located about 150 km from the volcanic center. The ash layers decrease in thickness only slightly with distance, as perceived from profiles sampled in flat areas. We conclude that the only noticeable erosional event in the region was the emplacement of the stone-line. This erosion event which was relatively short and mild in intensity, as part of the underlying soil derived from quartzdiorite was preserved. This soil formed above a saprolite with a thickness which may reach 150 m, a fact which supports the inference that the plateaus have been stable for millions of years, in contrast to the high erosion rates observed in the surrounding steep slopes and canyons. © 2006 Gebrüder Borntraeger.Ítem Seven good practices for the environmental licensing of coastal interventions: Lessons from the Italian, Cuban, Spanish and Colombian regulatory frameworks and insights on coastal processes(Elsevier Inc., 2018-11-01) Pereira, C.; Botero, C.M.; Correa, I.; Pranzini, E.; Universidad EAFIT. Departamento de Geología; Ciencias del MarEnvironmental licensing is the regulatory procedure that enforces the environmental impact assessment (EIA) of human activities inside a given country. Despite worldwide acceptance of EIA as a valid tool, its application in coastal environments is still too diverse and limited regarding the specificity of the natural processes influencing the shore. This paper compares the Environmental Licensing Procedure (ELP) of four countries, focusing on the activities that could affect the coastal geomorphology. The acquisition and validation of information were done through interviews with EIA representatives in each country, who signalized the official documents of environmental licensing and coastal management to be considered in the documentary review. The results present those differences and similarities among ELP stages in each country, based on the principles of the International Association of Impact Assessment and the national documents analyzed. In sum, 59 interventions associated with human uses and activities in the coastal zone were compared according to the prescriptive character of the environmental licensing in Italy, Spain, Cuba and Colombia. The natural processes influencing coastal geomorphology were also analyzed within the technical criteria included in the official guidelines for the EIA, finding a generalized weakness in processes associated with geochemical courses on coastal environments. By way of discussion, seven good practices are illustrated, according to their pertinence to the impact assessment of the coastal zone: 1) The integration of screening and scoping; 2) Evaluation focusing on the environment rather than the intervention; 3) Binding the coastal zone delimitation; 4) Institutional articulation; 5) Accreditation of environmental consultancies; 6) Official guidelines by types of environment; 7) The integration of environmental geographic information. Finally, general conclusions to assist EIA practitioners operating in the four countries and recommendations to lead further research are provided, introducing a novel process-oriented approach for ELP. © 2018 Elsevier Inc.