The region of study was MATOPIBA, located in the north of Brazilian Savanna biome (Cerrado), encompassing part of north/northeast of Brazil. The region has been gaining prominence in the last years due to the expansion of agricultural over this area. The aims of this study were: to adjust parameters for rainfall intensity-duration-frequency; and to identify the most vulnerable agricultural areas to erosion based on erosivity and erodibility. The rainfall intensity-duration-frequency function were adjusted using series of maximum annual rainfall event from 105 rainfall gauges. Gumbel model was the most efficient to simulate the maximum rainfall intensity, where these data were used to adjusted the rainfall intensity-duration-frequency model based on K, a, b and c parameters. The most rainfall gauges showed intensity between 51 and 80 mm h-1 and 81 and 120 mm h-1, respectively, for return period of 2 and 100 years with rainfall duration of 30 minutes. The higher rainfall intensity was observed mainly in the central-north of the region associated with rainfall systems. The rainfall intensity showed a huge capacity to cause soil erosion based on the erosivity energy, while the moderate erodibility was observed for areas with Ferralsols and Leptosols and low erodibility for areas with Arenosols.

Delimitation of watersheds and its morpho physiographic features are common practices used in hydrologic and environmental analysis. The aim of this paper was to analyze the Samambaia`s watershed and determine its morpho physiographic characteristics and track modifications made on land use throughout the years. Altimetry data was provided by SRTM radar program, compiled in a GIS created to store, process and analyze all the available data. A digital elevation model (DEM) was created from the SRTM image and used to delimitate the watershed. Final analysis of the morpho physiographic characteristics showed that Samambaia's watershed has a low propitious for floods. The region also showed intensification of urban areas when considering the last 25 years (≈20%).Additional keywords: morphometric; physiographic; use and occupation. ResumoA delimitação de uma bacia hidrográfica e sua caracterização morfofisiográfica são procedimentos comumente utilizados em análises hidrológicas e ambientais. O objetivo deste estudo foi determinar as características morfofisiográficas e as alterações no uso e no manejo do solo da bacia do córrego Samambaia, nos últimos 25 anos. As informações de altimetria da região foram extraídas de imagens SRTM, utilizando um software de processamento de dados e SIG, gerando um modelo digital do terreno, utilizado para a delimitação semiautomática da bacia hidrográfica. A análise destas informações determinou que a bacia do Córrego Samambaia possui características que mostram baixa propensão a cheias e inundações, apresentando também uma intensa urbanização ao longo dos últimos 25 anos (≈20%).Palavras-chave adicionais: fisiografia; morfometria; uso e ocupação.