GEOMORPHOLOGICAL EVOLUTION OF A RIVER CHANNEL AFTER SILTATION BY MUD AND DEBRIS FLOWS AND ENGINEERING WORKS: THE CASE OF THE JACAREÍ RIVER (COAST OF THE STATE OF PARANÁ, SOUTHERN BRAZIL)

Abstract

The role of gravitational processes in the geomorphological evolution of river channels is still a topic with little attention in the national literature. An example of this process is observed in the Jacareí River (coast of Paraná), which in March 2011 was affected by intense mud and debris flows. The objective is to analyze the geomorphological evolution of the Jacareí River in the face of the changes imposed by the gravitational processes of 2011 and anthropic interventions carried out before and after the 2011 event. Aerial photographs and orbital images (1953-2019) in a GIS environment were used to analyze the channel morphology and calculation of variables related to morphometry and morphodynamics. The Jacareí River has undergone geomorphological changes since 1953, with progressive loss of extension and sinuosity and oscillation between straight and sinuous patterns, caused by human interventions. The 2011 event imposed anastomosing pattern on part of the Jacareí River. With the reopening of the channel by machinery (return to the straight pattern) still in 2011, the Jacareí River was progressively adjusting to the new landscape configuration, presenting higher average lateral migration rates compared to the period prior to 2011. The results reinforce the idea of river resilience in the area. In this sense, the article presents recommendations for the research continuity.