Physiographic and morphometric attributes influence analysis in the definition of river basins susceptibility to debris flow occurrence

Abstract

Serra do Mar mountain range in state of São Paulo, Brazil, in the last 50 years, suffered a series of intense rainfall events that provoked many accidents related to superficial dynamic processes, with catastrophic social, economic and environmental consequences, especially in the cities of Cubatão, São Sebastião and Caraguatatuba. In 1967, in Caraguatatuba and São Sebastião municipalities regions, one of the most incredible landslides associated to movements already registered in Brazil occurred. In this way, the objective of the present research was to analyze the physiographic and morphometric attributes in relation to the river basins potentiality to the occurrence of mass movements, in the Serra do Mar of the north coast of São Paulo State. The studied area was divided in 13 physiographic units, involving plain compartmentalization; Serra do Mar cliffs and spikes; hills relief recessed by Camburu Fail; hilly terrain and terrain with hill with different characteristics in the Juqueriquerê Plateau; Paraitinga Plateau in the border of Serra do Mar cliffs; and hills and isolated hills. The results showed that river basins located in escarped portions, with high declivity and strong drained structure by fails, with valleys enclosed by mountains, like the physiographic unit II, present higher values to the morphometric parameters, which indicated higher potentiality to occurrence of mass movements. Therefore, the physiographic compartmentalization and the morphometric parameters analysis made possible the integrated evaluation of different physical environment attributes in relation to the susceptibility of river basins to the occurrence of mass movements, suggesting that the structural control of geomorphological evolution of these basins is a fundamental factor in both slope distribution with favorable directions to the slides occurrence and the morphometric parameters results.