Modelagem temporal da dinâmica do uso e ocupação do solo nas perdas e deposição de sedimentos na bacia do Rio Tapacurá (PE)

Abstract

Soil erosion is one of the most worrisome problems in the world, and is one of the main causes of environmental degradation. The objective of this study was to analyze changes in the use and occupation of the soil and its impacts on soil loss and sediment deposition in the Tapacurá River Basin, located in Pernambuco state. The future scenarios of use and occupation in the basin for t4 (2035): (a) Scenario 1: continuity of transitions and (b) Scenario 2: continuity of transitions and intensification of the livestock class and expansion of the urban area, were obtained using Land Change Modeler (LCM) and soil cover images from the years of 1989, 2007 and 2015. The prediction of soil use for the year of t3 (2015) was carried out using three methodologies: (a) Multi-Layer Perceptron Neural Network (RNMLP), (b) Similarity- Weighted Instance- Based Machine Learning Algorithm (SimWeight), and (c) Logistic Regression (LR) and for the methodology that showed better performance, the prediction of the future scenarios was executed. To estimate soil losses and sediment deposition, the Water and Tillage Erosion Model / Sediment Delivery Model (WaTEM / SEDEM) was used, as well as data on rainfall, elevation, use maps and soil types. For the years of 1989 and 2007, most of the basin was occupied by the classes: shrub vegetation, livestock and agriculture. For 2015, there was a reduction (77%) of the class of shrub vegetation when compared to the year of 1989. The results of the soil use forecast for the year of 2015 showed better performance using RNMLP, with Kappa index = 0,98. The simulation of the future scenarios showed an intensification of the transitions observed in the years of 1989, 2007 and 2015, in which the main uses of the soil were for agricultural activities, being the agriculture class the most representative. For all the years and scenarios studied, the highest soil losses and sediment deposition (> 100 ton/ha·year) were found in sites with higher LS factor variability and high erosion of the soil. The sub-basins Itapessirica, Água Azul and Bacias das Pacas had the highest sediment losses and deposition, around 47, 43 and 40 ton/ha·year, respectively. And the class, related to the anthropic actions, that presented greater susceptibility to the erosive processes in the basin was the agriculture.