Análise da vulnerabilidade ambiental da bacia hidrográfica do Rio Doce – RN

Abstract

The watershed of the Rio Doce-BHRD is located in the eastern portion of the State of Rio Grande do Norte. Is a geographical unit that comes over time, showing a disorderly occupation process, in its most varied forms. The diversity of existing environmental systems make it an area potentially vulnerable to negative environmental impacts. In this context, this thesis aimed to identify and map the spatial and geo-environmental characteristics and natural and environmental vulnerabilities of the watershed of the Rio Doce-RN, with operational and methodological support the Geotechnologies software free. As a result, proposed a new delimitation of the BHRD, in which there was an increase of 2.29% of the total area, your official passing of 387.8 km ² to 396.7 km ². Geoenvironmental characterization showed that the basin has suffered human actions which are changing the local landscape, turning areas that previously considered "preserved" in the area especially close to large urban centres and in the Guajirú basin. One of the most impressive activities include seasonal farming, responsible for removal of natural vegetation, including riparian forests, to the cultivation of monocultures, such as sugarcane; greenery, cultivated in the major and minor rivers bed Guajirú and Mudo and production in areas of rural settlements, the source of the Guajirú; growing perennial, with coconut, banana and cashew as the main cultures, observed in riverbeds, with emphasis on areas where the river has perennial characteristics, i.e. near the lagoon of Extremoz; urban sprawl toward the Mudo River, near the urban area of Ceará-Mirim, on the shores of the Lake to the mouth and Extremoz River Guajirú, with reference to the villages and districts like Serrinha, Massaranduba and urban areas of Extremoz and Natal; and the mining activity, in areas where outcrop geological formation Dona Inês. The result of these activities in the basin was reflected in natural and environmental vulnerabilities mappings. In the natural vulnerability of average degree reached level 4 vulnerability, classified as Medium stable/Vulnerable, equivalent to 2.1, with strong tendencies to become Moderately Vulnerable. This is the pressure in the urban areas located further east of the basin, which presents a most recent geology, with a geomorphology, soils and vegetation changed by human action, but minimized by more regular rainfall distribution. To environmental vulnerability, the results showed that the basin presents a 2-level average, 2.4-valued, considered the degree of vulnerability as a Moderately Vulnerable area. In this case, the influence of human actions in the Middle made these values reach 2.7 in urban areas, decreasing towards the West portion of the basin. It is concluded that the current stage of use and occupation of the basin. Therefore, the search for proposals that aim to minimize the negative impacts generated by the exploitation of natural resources existing there, with reference to the results obtained in this thesis, as well as other published in the scientific community, will make it possible to achieve social and environmental sustainability of the basin, keeping the balance morphogenesis/pedogenesis, as shown in the analysis of natural and environmental vulnerability.