Fluvial processes and landform in the Avulsive Big Ucamara System, Peruvian Amazon

Abstract:

The Avulsive Big Ucamara System is a large area consisting of three basins, Ucayali, Huallaga, and Marañón. The geotectonic and climatic history that created this exceptional fluvial system, was to support a complex mosaic of active and abandoned fluvial landforms. This region has an incomparable geodiversity, which is situated in the center of one of the largest remaining areas of intact forest on the planet, Pacaya Samiria Reserve, in Peruvian Amazonia. The large variability of fluvial landform occurred to avulsion and migration events in this big system makes a unique region in the world, due to the spatial reoccupation of old channels by new channels generating sub-adapted forms.

The first part explains a classifier to organize the “chaos” in the floodplain which exhibits a large variety of forms and processes. The processes have been defined in avulsion and migration processes and the features have been grouped into two distinct sets on the basin in relationship with the processes former. Thus, the main observation of the active, inactive channel (abandoned channel) and another fossil river landform suggests successive avulsion processes sequences of the Ucayali, Marañon, and Huallaga rivers. Ucayali, Marañon, and Huallaga rivers are the main drainage network or “parent channels”.

The second part, the main particularity feature in this area shows how there are several examples of the osage type (subadapted meander) rivers from the avulsive channel in the Ucamara System tend to follow over abandoned channels of larger formative rivers, in other words becoming on their parents’ channel helping to form the complex floodplain .

Our proposal in this work is to identify, classify, and characterize the different fluvial forms and processes that highlight the fluvial geodiversity and peculiarity of a unique system in the tropical rivers. Furthermore, to help understand the interaction of geomorphology and ecosystems, also recognizing the complexity of river networks like a promising tool to conserve riverine biodiversity as well as natural resources under global changes in climate and land use.