Morphodynamic modeling of meander cutoffs in the Huallaga River

Abstract:

The Huallaga river is a meandering stream and one of the main rivers in the Peruvian Amazon, it is also the longest tributary of the Maranon River flowing from Peruvian Cordillera Central and it is recognized as an Andean-Amazonian headwater of the Amazon River. The Huallaga River serves as an important aisle for the transportation of passengers and commercial goods, as it connects Yurimaguas city, the most important port town on the Huallaga River where the Peruvian Highway System from the Andes, and Iquitos, the largest city in the Peruvian Amazonian region. Currently, the dredging of its river bed is planned as part of a national waterway project, which aims to improve the safety of commercial vessels. However, adequate assessment of the impacts on river dynamics and geomorphology of such large-scale modification has not yet been carried out.

The meander cutoffs represent a natural natural river course shortcut that occurs due to this geomorphological dynamics, which locally increases the channel slope. It then triggers modification of the longitudinal river profile by diffusing out the nickpoint. An observation using 35 years of satellite images of the Huallaga River shows that there has been a meander cutoff and there is a meander loop that can develop a cutoff at any moment. In this study, development of the recent cutoff and the potential cutoff in the Huallaga river, and their effect on the longitudinal profile are investigated using a fully two-dimensional morphodynamic model. The model describes erosion and deposition processes at the river bed and the banks. Thus, it captures sediment flux from the banks to the channel bed, which can affect the longitudinal diffusion of the nickpoint. The results are discussed in terms of the effect on the change in geomorphology and slope upstream and downstream of the meander cutoff.