Geotecnologias de alta precisão no mapeamento de georisco a inundações frente às mudanças climáticas

Abstract

Flooding is the most common type of natural disaster worldwide and can have devastating consequences that affect the economy, environment and life dynamics of thousands of people. In addition, climate change and sea level rise have been accelerating and potentiating flood events, especially in coastal and riverine regions. However, are needy more studies of flood projections for the coming years, especially in local scale, with reliable geodetic references and which can guide mitigating actions. In this sense, the present doctoral thesis aimed to develop and apply methodology based on high vertical precision geotechnology in mapping flood geohazard in the front of climate change. This work was developed in two study areas in Brazil: (1) A cutout in the Piranhas-Açu estuary (study area 1), Rio Grande do Norte; and (2) a cut in the Uruguay River Basin (study area 2), Rio Grande do Sul. The choice of the two areas was because the regions has different types of floods (river flood x tidal flood) and with strong appeal scientific (social-economic-environmental). The methodology had as premise the use of high accuracy vertical ground control points, linked to the Brazilian Geodetic System and analyzed in a robust statistic for DEMs evaluation and calibration, developed and applied to the study area 1. Next, the methodology was employed for mapping the flooding geohazard in study area 2, a region under the influence of river flooding that comes with increasing trends of flood events. Finally, the methodology was applied to region 1 (region under the influence of tidal flooding). In this last stage, the current Intergovernmental Panel on Climate Change and Brazilian Institute of Geography and Statistics indicators on climate change and sea level rise for the year 2100 were taken as references. The results demonstrate high efficacy for the methodology of evaluation and calibration of DEM, obtaining evolutions in the reduction of the original DEM error by approximately 70%, as in the case of region 2 In addition, the mapping of floods, in both areas, demonstrate great robustness, validated with aerial photos and field records. The results of the flood hazard and risk mapping are alarming. The work proves that the annual fluviometric maximum level Uruguay River are in a positive trend and that the events of river floods will only increase. It was also found that approximately 118.26 km² of the Piranhas-Açú estuary is in an area of high risk and extremely high risk tidal flood, and in urgent need of mitigation measures. This thesis demonstrates that well applied techniques based on geotechnologies, such as remote sensing, GIS and high-precision geodesy, provide results that can be very effective for environmental management. The assessment of potentially floodable areas can help to reduce the negative impact of flooding events, supporting the land use planning process in areas exposed to the geo-hazard in focus.