Urban gullies in São Luis City, Maranhão State, Brazil

Abstract

Urban gully erosion is a serious problem in São Luís City, Maranhão State, Brazil. São Luís Municipality covers 831.7 km? and is situated in west-central Maranhão Island (2º19’09”-2º51’00” S; 44º01’16”-44º19’37” W). The Municipality is bounded by: São José de Ribamar (east); the Atlantic Ocean (north); Paço do Lumiar (west) and Rosário (south). The total population of the Municipality is 867,968; the vast majority being resident in urban areas (867,690) (IBGE, 2001). The occurrence of soil erosion involves a series of interrelated contributory factors, including: rainfall erosivity, soil erodibility, slope characteristics and vegetation cover. Urban gully erosion in São Luís City has resulted in loss of lives and property. Environmental conditions (soil properties, soil use, rainfall regime and slope characteristics) combined with deforestation and unplanned and unauthorized urban settlement expansion has promoted land degradation and initiated gully formation (Guerra and Hoffman, 2006). The lack of basic urban infrastructure, especially sanitation, adequate road drains and paved roads, has exacerbated the problem. In São Luís, a research project commenced in 2000, in which actively eroding gullies were identified and their evolution subsequently monitored. These gullies are in the districts of Salina, Sacavém, Araçagi, Castelão, Bequimão, Coeduc and Jaracaty.