Assessment of the Potentiality to the Debris-Flow Occurrence from Physiographic and Morphometrics Parameters: a Case Study in Santo Antônio Basin (Caraguatatuba, São Paulo State, Brazil)

This work aims to evaluate the potential for the debris-flow triggering from Santo Antônio hydrographic basin, located in the Serra do Mar region on North Coast of the State of São Paulo, Brazil, based on physiographic attributes, rainfall data, and morphometric parameters. For this purpose, hydrographic basin techniques were applied, assessing the vulnerability to the debris flow from geomorphological, geological, climatic, and anthropic aspects, and morphometric parameters relevant to the triggering of these processes in watersheds were calculated. Seven physiographic units were identified, which supported the understanding of geological and geomorphological aspects of the basin: coastal plains; river plains; colluvium and talus ramps; escarpments of Serra do Mar; upland of Paraitinga; mountainous relief and hillocks domain. The sub-basins located in steep sections of the relief, with high slopes, valleys, and channels docked, high drainage densities present higher values in the morphometric parameters, indicating a greater potential for triggering and occurrence of debris-flow processes. The joint analysis of physiographic compartmentalization with the identification of relief features, slope, amplitude, valley, slope shapes and morphometric parameters, is extremely relevant to recognize hydrographic basins susceptible to debris flows, as it integrates, and correlates aspects of the physical environment considered to trigger in the occurrence of these processes.