Modelagem do escoamento superficial e erosão hídrica em uma microbacia hidrográfica na região dos Tabuleiros Costeiros

Abstract

Water erosion is one of the main problems linked to tropical soils management, being the surface runoff responsible for the most part of sediments transported and deposited. This study has as objectives to determine total surface runoff and peak discharge, and to generate concentrated semi-empirical hydrological models, applying these models to soil losses model “Modified Universal Soil Loss Equation – MUSLE”, on a watershed occupied by eucalyptus plantations and native forest, in the Coastal Plain region, Aracruz county, Espirito Santo state, Brazil. Yellow Argisol medium/clayey texture (PA1), Yellow Argisol moderately rocky (PA8), and Haplic Plinthosol (FX) are the main soil classes of the watershed. Hydrological data were monitored between 1997 and 2004, with rainfall data being collected by automated weather station for obtaining the hyetograms. Hydrographs were generated with discharge data from precalibrated weir, with water-sensor level, installed on the stream flow control section of the watershed. Soil moisture was monitored up to 1.6 m depth. CN-SCS method did not produce good accuracy, overestimating the runoff and peak discharge for individual rainfall events. Semi-empirical models, based on rainfall characteristics, showed good estimates, and can be used for hydrological simulation. MUSLE model showed to be appropriated for soil losses predictions on the watershed being recommended the “a” and “b” coefficients equal to 14.96 and 0.59, respectively, with a topographical factor of 1.28. Soil use and management adopted on the watershed showed to be conservative, and this can be confirmed by the low soil losses on the watershed balance and on the stream flow control section.