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Study of morphological, pedological and sedimentological characteristics in valley bottoms and footslopes in a drainage basin situated in the Ibiúna Plateau

Grant number: 11/03909-4
Support type:Scholarships in Brazil - Master
Effective date (Start): August 01, 2011
Effective date (End): July 31, 2013
Field of knowledge:Physical Sciences and Mathematics - Geosciences - Physical Geography
Principal Investigator:Cleide Rodrigues
Grantee:Helga Grigorowitschs
Home Institution: Faculdade de Filosofia, Letras e Ciências Humanas (FFLCH). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

In this research we studied morphologies and relief positions with soils and deposits with hydric regimes characterized by temporary or permanent water saturation, with the following objectives: (i) characterization of soils and deposits located in lower slope sectors, valley bottoms and floodplains, with an emphasis on their hydromorphic properties; (ii) identification of degrees of hydromorphy in the soils and deposits of these sectors and morphologies, and representation of their spatial variability; (iii) development of propositions about the regime of water saturation in the studied areas and its relationship with the degrees of hydromorphy; (iv) development of propositions about the hydrodynamics of floods in the studied floodplain. Regarding the methodological aspect, the research was conducted according to the principles of the geossystemic approach, presenting an integrated analysis which considered the inter-relations among the studied variables. For this study, we selected two cross profiles in the Cotia River Drainage Basin, comprising lower slope sectors and valley bottoms, including a floodplain. Along these cross profiles, the following surveys were conducted: (i) topographic survey and construction of cross section graphics; (ii) description of the morphological attributes of soils and deposits, including detailed description of their hydromorphic properties; (iii) monitoring the water levels of the water table and perched water tables in the sites of description. The detailed characterization and analysis of the hydromorphic properties revealed gradations of intensity in them, and, based primarily on this, we developed a proposal for classification of the soils and deposits of the study area according to degrees of hydromorphy. We built two-dimensional graphical representations which illustrated vertical and lateral successions of different degrees of hydromorphy, and demonstrated its spatial variability across the studied sectors and morphologies. Thus, general trends were identified in respect to the occurrence and spatial distribution of the degrees of hydromorphy, and to its relationship with the regime of water saturation. One of the patterns identified consisted in the increase of the degree of hydromorphy in the soil profiles with increasing depth, associated with a longer duration of water saturation conditions in the deeper horizons. It were also observed significant differences in the intensity of the hydromorphic properties of the slopes, when compared to the valley bottom and floodplain areas. In this regard, lower degrees of hydromorphy were identified in the A and B horizons in the slope sectors, and higher degrees in the A and B horizons and in the depositional layers in the valley bottom and floodplain. These differences were ascribed to different regimes of water saturation, considering that, in general, the pedogenetic horizons and depositional layers with higher degrees of hydromorphy are subject to water saturation conditions of longer duration, when compared to those classified according to lower degrees of hydromorphy. Concerning the issue about the hydrodynamics of floods in the studied floodplain, we identified morphologies that preferentially receive the overflowing river flows and have higher deposition rates, and sectors with lower deposition rates, where flooding is less frequent and there is a predominance of fine sediments deposition. (AU)

Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
GRIGOROWITSCHS, Helga. Study of hydromorphic properties of soils and deposits in lower slope sectors and valley bottoms in the Cotia Drainage Basin/Ibiúna Plateau. 2013. Master's Dissertation - Universidade de São Paulo (USP). Faculdade de Filosofia, Letras e Ciências Humanas São Paulo.

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