An Analyses of land use in the sub-basin of Itajaí-Mirim River in the state of Santa Catarina and stages of permanent preservation areas

Código

I-EBHE0081

Autores

Juliana Moreira da Silva, Carolina Schmanech Mussi, Paulo Ricardo Schwingel

Tema

WG 1.03: Urban Water - Urbanization phenomenon & adequate water management

Resumo

Watersheds and riparian forests, predominantly located in areas of human activity, present challenges for water resource management. Intense land-use changes associated with urbanization exert pressure on these environments. Thus, city planning must incorporate the investigation of land use changes through geoprocessing to identify priority areas for the preservation of watercourses and the restoration of regions critical to ecosystem function. The Itajaí-Mirim River sub-basin is the area of this research. The study aimed to analyse land use evolution within the sub-basin from 1985 to 2020 and to assess the state of conservation of the Permanent Preservation Areas (PPAs) of the sub-basin. The Itajaí-Mirim River sub-basin, a tributary of the Itajaí-Açú River, is in the north-central region of Santa Catarina. Initially, the study utilized land cover map data from the MapBiomas platform, covering a 35-year span from collection version 6. Land use feature classes were adapted from MapBiomas; using QGIS v.3.20 software, matrix files were converted to vectors, and classes were reorganized by selecting attributes (SQL). The area of each landscape class was calculated. For the analysis of the state of the PPAs, the Rapid Environmental Assessment Protocol was adapted, a method for assessing environmental stress with a focus on forest protection of the banks. The course of the Itajaí-Mirim River was divided into 17 stretches of 10 km each. This was overlaid with preservation areas data from buffer limits according to the Forest Code, and land use data, previously obtained, using the Union. Finally, an assessment was made of the state of the green areas in the preservation areas, with scores of critical, reasonable, good, and excellent, and a matrix assessing the state of environmental preservation in 1985 and 2020. The Forest Formation class occupies 62% of the area, followed by the agriculture class at 24%. The basin experienced an 88% urban expansion during the period, accompanied by a 3.5% decrease in natural areas. Similar trends were noted in the neighboring Camboriú basin and the coastal municipalities of Porto Belo and Bombinhas (SC), where tourism significantly influenced land use, pushing agriculture inland, reducing natural spaces, and leading to the vertical growth of urban centers like Balneário Camboriú (SC) and Itajaí (SC). Following an analysis of the Permanent Preservation Areas revealed that river stretches 1 to 10 and 15 to 16, within the sub-basin municipalities of Itajaí, Brusque, Guabiruba, Botuverá, and Vidal Ramos, are in a critical state of conservation. Conversely, stretches 12 and 13 of the Itajaí-Mirim river were in good condition, and even excellent in 1990 and 1995. In Itajaí, land use conflicts within the PPAs are predominantly agricultural (41%) and urban (37%) in stretch 1. However, the stretch 17, maintains a good state of conservation, with agriculture accounting for 15% of its use. In summary, effective water resource management necessitates urban planning and land use management within basins, as well as collaborative efforts from administrators, economic sectors, and society to establish sustainable urban development strategies that minimize the risks associated with human activities and promote successful basin restoration initiatives.