Examinando por Materia "Deltas"

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    Dinámica costera durante el Mioceno tardío - Plioceno temprano al norte del Cinturón Plegado Sinú - San Jacinto, Colombia
    (Universidad EAFIT, 2021) Cárdenas Gómez, Claudia Patricia; Cárdenas Rozo, Andrés Leonardo; Rincón Martínez, Daniel Andrés
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    Exploring the spatial patterns of delta morphodynamics on Mars and Titan
    (Universidad EAFIT, 2020) Vargas Londoño, Juanita; Paniagua Arroyave, Juan Felipe; Palermo, Rose
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    Human induced discharge diversion in a tropical delta and its environmental implications: The Patía River, Colombia
    (ELSEVIER SCIENCE BV, 2012-03-06) Restrepo, Juan D.; Kettner, Albert; Universidad EAFIT. Departamento de Geología; Ciencias del Mar
    The Patía River, the number one in terms of sediment yield ~1500tkm -2yr -1 draining the western South America, has the most extensive and well developed delta on the Pacific coast, measuring 1700km 2. During the Holocene, nature forced the Patía delta to the south; however, a major water diversion, starting in 1972, diverted the Patía flow to the Sanguianga River, the latter, a small stream draining internal lakes from the Pacific lowlands. This human induced discharge diversion shifted the active delta plain back to the north and changed the northern estuarine system into an active delta plain. Overall, major environmental consequences of this discharge diversion in terms of morphological changes along the delta coast and distributary channels, are evidenced by: (1) coastal retreat along the abandoned delta lobe; 63% of the southern shoreline is retreating at maximum rates of 7myr -1, with a corresponding coastal land loss of 106myr -1; (2) transgressive barrier islands with exposed peat soils in the surf zone; (3) abandonment of former active distributaries in the southern delta plain with associated closing of inlets and formation of ebb tidal deltas; (4) breaching events on barrier islands; and (5) distributary channel accretion in the northern delta plain by morphological processes such as sedimentation (also in crevasses), overbank flow, increasing width of levees, interdistributary channel fill, and colonization of pioneer mangrove. The Sanguianga Mangrove National Park (SMNP), the largest mangrove reserve in Colombia, measuring 800km 2, lies in this former estuary, where major hydrologic and sedimentation changes are occurring. Observed environmental changes in the SMNP, include (1) seaward advance of the sub-aqueous delta front at the Sanquianga inlet evidenced by an increase in tidal flat area from 5.4Mm 2 in 1986 to 14Mm 2 in 2001; (2) freshening conditions in the Sanguianga distributary channel, a hydrologic change that has shifted the upper estuarine region (salinity <1psu) downstream; (3) downstream advance of freshwater vegetation, which is invading channel banks in the lower and mixing estuarine zones; (4) die-off of approximately 5200ha of mangrove near the delta apex at Bocas de Satinga; and (5) recurrent periods of mangrove defoliation due to a warm plague. Further analysis indicate that during the past two decades, processes such as mangrove erosion in the delta shore, are the result of a short-term relative sea-level rise of 5.1mmyr -1 for the 1984-2006yr-period, after the devastating tsunami of 1979. In the Patía catchment, erosion rates have been more pronounced during the 1970-1980 and 1990-2000 decades, as a result of land degradation and deforestation. Preliminary results indicate that relative resent anthropogenic influences on the Patía River drainage basin have altered the deltaic environment and beyond significantly. © 2011 Elsevier B.V.
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    Morphodynamics of a high discharge tropical delta, San Juan River, Pacific coast of Colombia
    (ELSEVIER SCIENCE BV, 2002-12-30) Restrepo, JD; Kjerfve, B; Correa, ID; Gonzalez, J; Universidad EAFIT. Departamento de Geología; Ciencias del Mar
    The San Juan River has one of the most extensive and best developed deltas on the Pacific coast of South America, measuring 800 km2. The river drainage basin measures 16465 km2 and is located in one of the areas with the highest precipitation in the western hemisphere. The annual rainfall varies from 7000 to 11 000 mm, and as a result the San Juan River has the highest water discharge (2550 m3 s-1), sediment load (16×106 t yr-1), and basin-wide sediment yield (1150 t km-2 yr-1) on the west coast of South America. The San Juan delta growth began approximately 5000 years BP. The structure of the delta is determined by the interactions between fluvial deposition and the effect of 1.7-m significant swells, mostly from the SW, and strong tidal currents. Analysis of delta progradation indicates that during 1848-1992 the morphology of the delta was characterized by beach ridge accretion, spit growth, narrowing of inlets, and a general advance of the delta shoreline. During the past decade processes such as rapid erosion of the delta shore, narrowing of barrier islands, and breaching of a new inlet, are the result of a long-term relative sea-level rise of 2.6 mm yr-1 due to tectonically induced subsidence coupled with a eustatic rise of sea-level. The delta also experiences strong oceanographic manifestations associated with the El Niño-La Niña cycle, causing regional sea-level elevation of 20-30 cm during El Niño years. Recent coastal subsidence in the delta is evidenced by (1) increased occurrence of non-storm washover events; (2) increased erosion of barrier islands with average loss of 11 m yr-1 during 1993-1997; and (3) a relative sea-level rise of 3.4 mm yr-1 during 1991-1999. The morphology and recent evolution of the San Juan delta are unique when compared to other deltas of South America because of the singular combination of extreme climatic, geologic, and oceanographic conditions under which the delta has formed and the absence of human-induced impact in the drainage basin. © 2002 Elsevier Science B.V. All rights reserved.
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    Reconstrucción paleoambiental de la Formación El Floral – Ciénaga de Oro a partir de una sección estratigráfica entre los municipios de Montería y Planeta Rica
    (Universidad EAFIT, 2017) Castillo Guerra, Silvana; Soto López, Laura; Cárdenas Rozo, Andrés Leonardo