Determinação de perfil de cotas vinculado ao sistema geodésico brasileiro para áreas de risco a inundação na fronteira oeste do Rio Grande do Sul

Abstract

The cities bordering the hydrographic region of the Uruguay River, on the border of the state of Rio Grande do Sul, are affected by natural eventualities such as floods and overflow. These events bring with them, due to their intensity, extension and repeatability, many problems and social discomfort, which subject the municipality to several situations that require both immediate and long-term interventions by the competent authorities. It is in this context that the studies and applications of the geodesic sciences allied to the topography enter, presenting real solutions, based on the previous knowledge of situations, and the guarantee of successes in the applicability of its practical resources. Among the many existing tools, this work presents a topographic profile of a section near the banks of the River, linked to the Brazilian Geodetic System for the cities under study, whose methodology was based on a geometric leveling and counter-leveling of the nearest RN and the linimetric rules and its subsequent computation in spreadsheet, techniques for tracing the NRNN and strategic points by GNSS / GPS, as well as the post - processing of data to obtain the geoidal undulation and the determination of the orthometric point of the points through the method of data combination . The maximum dimensions of ANA readings from the year 1940 to 2017 were studied and analyzed, and next to the knowledge of the field of study, these dimensions were separated into three intervals to allow the subsequent classification of risk. For the classification of High, Medium and Low Risk, the criteria of the Institute of Technological Research and National Civil Defense were considered, based on the concept of danger and vulnerability. For the city of São Borja, the profile, which leveling was 558.1m, comprises the zero bound of the linimetric rule, with H = 47, 347m at the height of a point P2, with H = 66.7316m. In Uruguaiana, the profile, with a level distance of 401.9 m, shows the zero dimension of the corresponding rule H = 38.6624m and the RN quota which H = 60.4254m. The obtained profile is represented in graphical-numerical form and shows that the applied methodology was efficient for the determination and classification of the risk in this section, once the precision obtained in its stages was satisfactory. Thus, the defined risk zone agrees with the reality observed in flood events, and the ANA quotas linked to the GBS represent the topographical features in this section limited to affected areas.