Topographical threshold of gully erosions in Piratininga (SP)

Author(s)

Rodrigo Augusto Stabile

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Letras e Ciências Humanas (FFLCH/SBD)
• Defense date: 2013-01-30

Examining board members

Bianca Carvalho Vieira; Nelson Ferreira Fernandes; Leonardo José Cordeiro Santos

• Advisor: Bianca Carvalho Vieira

Abstract

Considering the importance of defining the critical conditions for the generation, development and stabilization of gullies and other erosional features, and taking into account the few approaches accordingly held in Brazil, the aim of this research is to evaluate the topographical critical limits for developing of gully erosion in Piratininga (SP). The methodological procedures involved: the identification and characterization of the gullies using aerial photographs and in situ; measurement of the slope (S) in the field and with various resolutions of Digital Terrain Model (DTM) and drainage area (A) also from DTM, and the definition of topographical thresholds in the form of following Power Function: S = a × . The topographical threshold line has been set at the lower limit of data, parallel to the slope of orthogonal regression line of S and A. The erosional features were categorized into 4 classes and 13 subclasses according to their morphometric aspects and indicators of active processes. The measurement of S and A by different methods resulted in some significant changes in the data generated, particularly when comparing the values obtained in the field and the DTM. We obtained the following topographic threshold: S = 0,064 × , which has coefficients similar to other studies that analyzed erosional features resulting from subsurface flow. The distinction between active and stabilized gullies, as well as analysis of the starting points of erosion in relation to threshold line, provide an empirical basis for the discussion of the evolution of gullies in relation to the topographic threshold line and also for the understanding of stable and active states of gullies, allowing the construction of a theoretical model for predicting the stability and instability of the gullies based on the relationship between slope and drainage area in different slope profiles. (AU)

• FAPESP's process: 09/06660-7 - Slope hydrologic dynamics and gully erosion on the Água da Faca Basin, Piratininga (SP)
• Grantee: Rodrigo Augusto Stabile
• Support Opportunities: Scholarships in Brazil - Master