Iván D. Correa

Morphodynamics of a high discharge tropical delta, San Juan River, Pacific coast of Colombia

Abstract The San Juan River has one of the most extensive and best developed deltas on the Pacific coast of South America, measuring 800 km 2 . The river drainage basin measures 16 465 km 2 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 m 3 s −1 ), sediment load (16×10 6 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 Nino–La Nina cycle, causing regional sea-level elevation of 20–30 cm during El Nino 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.

Coastal erosion and village relocation: a Colombian case study

Because of its tectonic setting, the Pacific coast of Colombia is subject to a variety of geological hazards, including earthquakes, tsunamis and associated phenomena such as regional and local coastal subsidence, flooding and soil liquefaction. Erosional trends are prevalent along much of the 700 km long, low barrier islands shorelines of the Pacific littoral and land losses are enhanced by factors such as 30 cm regional sea level rises associated to the occurrence of El Nino. Marine erosion is threatening more seashore littoral villages and worsening the already difficult socioeconomic conditions of most part of the inhabitants. Because of diverse and strong motivations to stay near the sea, the responses of barriers islands inhabitants to marine erosion has consisted in most cases of repetitive in-shore and along-shore directed relocations of villages, rather than definitive abandonment of the islands. In the long run, this procedure only has postponed the problem and led to repetitive relocations and economical losses. The recent inland relocation of El Choncho village, on the San Juan River delta, illustrates a different response to marine erosion. Although a new along-shore relocation was physically possible, inhabitants decided to abandon the barrier island and migrate to an interior, ancient beach ridge complex, applying a prudent solution which will be the most appropriate for other threatened villages of the Pacific littoral. A detailed geomorphologic mapping program must be conducted in order to identify appropriate sites for inland relocation of existing villages on the barriers islands of the Colombian Pacific coast.

Impact of terrestrial mining and intensive agriculture in pollution of estuarine surface sediments: Spatial distribution of trace metals in the Gulf of Urabá, Colombia

The Gulf of Urabá (northwestern Colombia) is a geostrategic region, rich in biodiversity and natural resources. Its economy is mainly based on agribusinesses and mining activities. In this research is determined the impact of these activities in bottom surface sediments of the estuary. Thus, grain size, total organic carbon, total nitrogen, carbonates, Ag, Al, Ca, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb and Zn concentrations from 17 surface sediment samples were obtained and enrichment factors (EF) as well as geo-accumulation indices (Igeo) were calculated to determine the contamination level in the gulf. EF and Igeo values revealed that the estuary is extremely contaminated with Ag and moderately contaminated with Zn. Therefore, the observed enrichment of Ag may be explained as a residue of the extraction of gold and platinum-group metals and the enrichment with Zn associated mainly to pesticides used in banana plantations.

Factors Influencing the Distribution and Characteristics of Surface Sediment in the Bay of Cartagena, Colombia

ABSTRACT Restrepo, J.C.; Escobar, J.; Otero, L.; Franco, D.; Pierini, J., and Correa, I., 2017. Factors influencing the distribution and characteristics of surface sediment in the Bay of Cartagena, Colombia. This study evaluated patterns of coastal sediment movement and deposition under different seasonal conditions (warm and cold phases of the El Niño–Southern Oscillation [ENSO] and normal conditions) in Cartagena Bay, Colombia. A calibrated numerical model (MOHID modeling system) was applied to assess the spatial distribution of sediments transported by the Canal del Dique to the bay and studied the spatial distribution and major textural characteristics of 234 surface sediment samples. Currents in the Bay of Cartagena are controlled primarily by the strength and direction of the wind. Model results show major sediment deposition in the southern sector of the bay during the dry season. More homogenous spatial distribution of sediments throughout the Bay of Cartagena occurs with an increase in river inputs from the Canal del Dique. These patterns were enhanced or weakened, respectively, by cold and warm phases of the ENSO. Predominant sediments were medium size (ϕ = 5.35 ± 1.2), poorly sorted (σ = 1.63 ± 0.8), with notable asymmetry (Sk = −0.052 ± 0.2) and kurtosis (k = 0.84 ± 0.4). Sediments with lower sand content (<5%) are located along a latitudinal axis from the Canal del Dique delta to the western end of the island of Tierrabomba. CaCO3 content of the sediments is <10%. Water and sediment flow, controlled by the Canal del Dique, has favored the transport and deposition of poorly sorted, symmetric, and mesokurtic mud in most of the Bay of Cartagena. As a result, autogenous calcareous sediments have been covered by fine terrigenous sediments that were delivered via the Canal del Dique. Thus, the channel plays a more prominent role in sediment transport and deposition in the Bay of Cartagena than thought previously.

The Historical, Geomorphological Evolution of the Colombian Littoral Zones (Eighteenth Century to Present)

The complex geological framework of Colombia is reflected on its Caribbean and Pacific coasts by the highly contrasting nature of their littoral types, ranging from low-relief deltaic barrier islands and mangrove swamps to steep-rocky reliefs cut by plunging cliffs and wide erosional shore platforms. Relative sea-level changes during the Quaternary and the Holocene are evidenced by morphological features of ancient coastline positions, including emerged marine terraces with coral reefs, cliffs, stacks, and raised beach ridges deposits.