Hydrogeological investigation: a case study to verify flood zones in areas of urban expansion

Abstract

The alterations that occurred by the use and occupation of the soil interfere directly in the local environmental quality, especially in urban expansion areas, when the soil, which has been used only for agricultural practices until then, starts receiving the necessary infrastructure to implement allotments. In this sense, the hydrogeological investigation of flood zones becomes fundamental, since it orientates the establishment of the existence or non-existence of water sources and therefore of the delineation of permanent preservation areas or the deployment of proper infrastructure to allocate subsurface water. The study area is located in the north of the state of Paraná in the city of Ibiporã, where residual soils of basaltic rocks belonging to the Serra Geral Formation. In this locality, there are occasional records of seasonal occurrences of water with the formation of temporary drainage networks, thus allowing environmental agencies to partially prevent the use and occupation of the soil. Thus, geotechnical and hydrogeological studies are needed to determine whether these points come from natural groundwater or form by saturating the porous medium via surface runoff, in this latter case, there is no legal impediment to the occupation of the settlement. For this study 9 drill shafting boreholes were performed and historical sensor imaging, that originated in the making of 4 hydrogeological sections and analysis based on the hydrological potentials. For this study, 9 drill holes were drilled using mechanical auger and historical evaluations of orbital images, which resulted in the making of 4 hydrogeological sections and analyzes based on hydraulic potential, integrated with the morphological conditions and evolution of land use. The results showed that the existence of intermittent drains in the place originated by mechanical modifications in the terrain and the occasional water appearances are due to rainwater saturation, evidenced by the direction of groundwater flow influenced by the hydraulic potential of the porous medium.