Morphological and mathematical analysis of asymmetrical fluvial pattern: A study case from the Ucayali River (Peru)

We analyze the asymmetrical pattern of the lower part of the Ucayali River. The asymmetrical pattern is expressed at different scales: meander belt, channel pattern, and rate of meander migration. Relations that exist between river trends, floodplain margin, and neotectonic faults suggest that active deformation controls the river pattern. The use of mathematical analysis of images allowes a more accurate analysis of meander migration. Shape entities related to fluvial morphology have been delimited on the initial SPOT XS scene. The image has been processed using non-linear methods, morphological opening and geodesic reconstruction. Then, we used the Adonis processing to analyze the remaining curves, that are related to the most prominent elements of the scroll pattern. Traces of the meander evolution are obtained, more accurately and quicker than by eye. The floodplain side meanders are developing independent of the river trend, and the meanders on the bluffline side of the floodplain are controlled by the bluffline trend. This result is coherent with other neotectonic data, and suggests that rivers are affected by ongoing deformation of the flood plain along the craton margin.