The Continental Delta of the Arauca River in Colombia And It’s Distributive Drainage System

The Arauca River, which serves as part of the international geographical boundary between Colombia and Venezuela, in the Eastern Plains area between the two countries, originates high up, in the Ritacuba peaks of the Sierra Nevada of Cocuy, a natural park in the Colombian Andes, at over 5,300 meters above sea level. Entering the immense extension of flat lands, it generates a large distributive drainage system that gives rise to a continental delta still in formation.

The term "continental delta" refers to a mega alluvial deposit, similar to an alluvial fan or dejection cone, but of kilometric extension, which develops mostly in the tropical zones due to the high rainfall and high sediment production associated with extensive piedmont fronts along high mountain ranges. Such is the case of the Arauca river delta, with an extension of over 80,000 km², a distributive drainage system with large avulsive processes triggering a deltaic morphology over a very flat land surface.

Over the last 100 years, the avulsive nature of the river has generated distributive channels that have facilitated lateral migration in the plain, generating deposition and redistribution of flows along large lobes of sediments. This peculiar behavior creates a particular morphological arrangement in the flat lands, which generate marshes, “esteros” and wetlands with an impressive variety of live forms. The volumes of sediment transported are high, generating major morphological changes in relatively short periods, favoring lateral movement of the river, diffusion, avulsion, the creation of new channels and the closure of previous ones, with extensive and largely compartmentalized flooding.

This article presents the characteristic morphodynamic behavior of distributive drainage systems in continental deltas, with particular reference to the variable conditions generated in the floodplain areas of the Arauca River, which make it difficult to predict, prevent and mitigate local flood conditions in successive periods.

KEY WORDS

Continental Deltas, Distributive Drainage Systems