Análise das condicionantes ambientais da bacia hidrográfica de San Idelfonso - província de Trujillo, Peru

Abstract

The motivations for establishing a community in a particular region can be diverse. In South America, especially in Peru, due to the lack of knowledge of the history of the areas, the positioning of the settlements was not always the most adequate. The omission of the environmental variable has negative effects up to the present day. This is the case in the province of Trujillo in Peru, where urban development has taken place on the riverbed of an intermittent river, which, when activated in events of high rainfall, causes, in addition to debris flow, the flooding of the urban area. The consequences reach not only the environmental level, but also the economic and social one, since in addition to the debris coming from the mountainous area of the basin, solid residues are also dragged along the riverbed, together with sediments, residues, and water to the urban area of Trujillo. It is currently possible to think about mitigating or eliminating the consequences of these events and at least understanding the events. With the support of geotechnologies and modeling, it is possible to understand the dynamics of these situations and model the responses to solve or at least minimize the problem. In this work, historical data on precipitation, area composition, evolution of land use and land cover and relief were used, which are directly related to the environmental condition of the basin and served as input for the precipitation-flow, slope stability and flood modeling. The subsequent union of all characterization data, including bibliographic materials, gave rise to a proposal for environmental zoning for the basin. The characterization of the basin indicates a marked variation in altitude in the mountainous area, with equally accentuated slopes. The mountainous part of the basin, where intermittent water resources originate, is mostly composed of grandiorite, a highly fragmentable material. And the groundwater, even in the mountains, has great variation and rapid saturation. The land use over time varied in the plain area, being disorderly converted into an urban area. Regarding slope stability, 3% of the basin area (0.33 km²) is classified as unconditionally unstable, unsaturated, in areas where there is accumulation of sediment. Considering the precipitation data (1963-2019), there was an increase in precipitation over time. The results of the HEC-RAS were inconclusive, due to the lack of flow data for the basin and intermittent flow behavior. The requalification of the zoning of the basin has actions of low to high complexity, which together have the potential to minimize the impacts of flooding. It is concluded that the environmental condition of the basin in face of El Niño events is critical, as the factors that anthropically and naturally make up the basin, already contribute to flooding separately. And it is understood the need for actions that minimize these impacts, suggested through environmental zoning. It is also suggested to prepare a diagnosis of the other quebradas that reach the districts of the province of Trujillo. [resumo fornecido pelo autor]