Urban Gardens and Soil Compaction: a Land Use Alternative for Runoff Decrease

After several landscape transformations caused by human activities, finding a suitable environment becomes increasingly challenging in urbanized regions. The predominance of non-permeable areas results in a low level of water infiltration. Notwithstanding, even green areas can have high runoff rates, since soil compaction has a decisive influence on the water movement. In places that have a natural predisposition to overflow, these problems are more significant. This study aimed to investigate causes of flooding, highlight the benefits of urban gardening and to propose urban gardening as an alternative to soil improvement in the Corujas Watershed, São Paulo, Brazil. The evaluation was based on: (a) the physical characteristics of the watershed, provided by morphometric analysis and land-use analysis; and (b) the soil compaction rates of an urban garden compared to a riparian forest and a grass area. The morphometric results indicated that the watershed has a significant flood tendency, and the land use map demonstrated that 29.55 % of the soil has some permeability. Nevertheless, this permeability currently varies according to soil management and cover. The grass area presented the highest compaction rates, the riparian forest a medium rate, and Corujas Garden the lowest rate. The garden also has green infrastructures and good management practices, which have led to the appearance and perpetuation of diffuse springs. These results showed that the urban garden activities could improve the physical characteristics of the soil and optimize water infiltration. Subsequent studies will investigate whether this characteristic also applies to other gardens located in different urban watersheds.