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Caribbean Coast: Gulf of Urabá
Within the Gulf of Urabá (Fig. 2), rock outcrops along the coast are mainly basaltic lavas, agglomerates, and Tertiary sedimentary rocks. The Quaternary is represented by sandy-muddy alluvial deposits and sandy beach-ridge complexes located between cliff headlands (Ingeominas 1992).
The Gulf of Urabá is a relatively wave protected environment with a general NS orientation and a maximum width of 20 km at its northern end (Fig. 2). At its northeastern part, the Gulf shores are typically characterized by narrow erosional beaches, backed by cliffs cut into sedimentary sequences of the Sinú Belt (Figs. 28 and 29). South of Necoclí, the Gulf of Urabá is dominated by deposition associated with recent human activities, the Turbo River delta being the most important (Figs. 30 and 31).
Figure 28. Aerial view of Necoclí, located on an erosional marine platform up to 4 m high. Photo by R. Morton. |
Figure 29. Radar image of the southern part of the Gulf of Urabá, showing the location of Necoclí and Turbo, and the Turbo River delta. The "bird foot" Atrato River delta is on the west side of the Gulf. Reproduced by permission of Universidad Eafit. |
Figure 30. Radar image of the recent Turbo River delta (top center) and the Las Vacas spit, between Turbo and Punta Las Vacas. Dotted lines represent the 1958 coastline position, prior to the relocation of the river from the Bay of Turbo to its current mouth. Reproduced by permission of Universidad Eafit. |
Figure 31. Aerial view of the northern shores of Las Vacas spit, protected with groins (ineffective) and riprap. Photo by I. Correa. |
The east side of the Gulf of Urabá (Fig. 28) is defined by the prograding Atrato River delta, which has 16 active distributaries (Fig. 32) protruding into the 25-m-deep Gulf. The Atrato River is 730 km long and drains an area of about 36,000 km2 of the western Colombian Cordillera and the Serranía del Baudó, on the Pacific Coast. Rainfall in its drainage basin is 8 m/yr, which supplies a mean water discharge of 2700 m3/s and a sediment yield of about 11 x 106 ton/yr (Restrepo and Kjerfve 2000).
Figure 32. Aerial view of El Roto Branch of the Atrato River delta showing delta accretion. Intertidal flats beside the levees are vegetated by mangroves. Photo by R. Morton. |
Northwest of the Gulf of Urabá and the Atrato River delta (Fig. 2), the Caribbean coast changes its character to a basaltic-cliff coast (Fig. 33) with wide alluvial valleys and beach-ridge shores (Fig. 34). Absence of sediments from the Atrato River permit the development of fringing coral reefs that become progressively more abundant toward Panamá (Díaz 2000).
Figure 33. Aerial view of the northwestern coast of the Gulf of Urabá, consisting of basaltic cliffs, small pocket beaches, and erosional stacks. Reproduced by permission of Invemar. |
Figure 34. Beaches of Acandi, Colombia near the border with Panama. Photo by I. Correa. |
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