Examinando por Autor "Restrepo A, Juan D."
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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 El impacto de la deforestación en la erosión de la cuenca del río Magdalena (1980-2010).(Academia Colombiana de Ciencias Exactas, Físicas y Naturales, 2015-06-01) Restrepo A, Juan D.; Universidad EAFIT. Departamento de Geología; Ciencias del MarEn la última década, la cuenca del río Magdalena ha experimentado un incremento en las tasas de erosión del orden del 34 %, pasando de 550 t km-2 a-1antes del año 2000 a 710 t km-2 a-1 en el periodo 2000-2010, con un aumento en el transporte total...Ítem Monitoring water discharge and floodplain connectivity for the northern Andes utilizing satellite data: A tool for river planning and science-based decision-making(ELSEVIER SCIENCE BV, 2020-07-01) Restrepo A, Juan D.; Kettner, Albert J.; Brakenridge, G. Robert; Universidad EAFIT. Departamento de Geología; Ciencias del MarRiver discharge data and magnitudes of floods are often not readily available for decision makers of many developing nations, including Colombia. And this while flooding for these regions is often devastating, causing many fatalities and insurmountable damage to the most vulnerable communities. During the we season, in strong La Nina years, infrastructural damages of over $US 7.2 billion have occurred. Mitigation of such natural disasters lacks data-supported scientific approaches for evaluating river response to extreme climate events. Here, we propose a satellite-based technique to measure river discharge at selected sites for the main northern Andean River, the Magdalena. This method has the advantage of back calculating daily river discharges over a period of two decades, and thus making it possible to calculate return intervals of significant flood events. The study shows that satellite based river discharges well capture a) the inter-annual variability of river discharge; b) the natural seasonality of water discharge along the floodplains; and c) peak discharges that were observed during La Nina conditions between 2008 and 2011. The last is likely more accurate compared to ground-based gauging stations, as ground-based stations tend to overflow during large flood events and as such are hampered to accurately monitor peak discharges. Furthermore, we show that these derived discharges can form the base to study river-floodplain connectivity, providing environmental decision makers with a technique that makes it possible to better monitor river and ecosystem processes.Ítem Satellite-Based Estimation of Water Discharge and Runoff in the Magdalena River, Northern Andes of Colombia(Springer, 2017-01-01) Escobar, Rogger; Restrepo A, Juan D.; Brakenridge, G. Robert; Kettner, Albert J.Satellite-derived data provide important information about river characteristics such as channel geometry, water surface area, water levels, and floodplain extension (Rokni et al. 2015; Schumann and Moller 2015; Smith 1997)