A concept for integrated investigations of karst phenomena in urban environments : merging geophysical and hydrometrical investigations with 3D hydrogeological modeling for applied urban hydrogeology within a gypsum karst area

Theories that describe karst systems are often limited to conceptual models. However, engineering projects within complex karst systems demand the development of tools that allow site-specific descriptions of the hydrogeologic settings and calibrating the processes of karst evolution. Subsidence of a river dam and an adjacent highway, both constructed on gypsum-containing rock, southeast of Basel, Switzerland, required remedial construction measures. A monitoring network was set up, to safeguard surface and subsurface water resources during the construction measures. The primary project goal was to develop tools that enable a continuous characterization of the groundwater flow regime and that facilitate the evaluation of the long-term performance of the infrastructures. Investigative methods included high-resolution 3D hydrogeological modeling, and the integration of geological, hydrometrical and hydrogeophysical field data of varying quality. Particular focus was placed on the hydraulic behavior of the complex conduit system. Results help to understand the evolution of distinct karst features and zones of preferential flow. The location of fracture zones and parts of the old meandering river course, playing a major role in the karst evolution process, could be identified. Together with the hydrometrical investigations and hydrogeological modeling, the evolution of the karst system and its dynamics can be interpreted in relation to the groundwater flow regime. Hydrogeologie des unteren Birstales, Grundwasser