Modelling of shallow groundwater levels and interaction with drainage system and streams under the impact of climate change

ABSTRACT Under the impact of climate change, groundwater levels are anticipated to increase in temperate climatological zones with increased precipitation and sea level rise. Urban areas located at low elevations are especially at risk, and increased shallow groundwater levels can lead to flooding, water seepage into basements, capacity problems in water infrastructure, etc. Furthermore, old sewer systems can act as drains by allowing groundwater to seep into the sewer system. This process can artificially maintain the groundwater level low, and therefore if the sewer system is rehabilitated, the problems are even increased further if necessary solutions are not included in the planning process. In this article, we analyze an urban catchment in Aalborg, Denmark, which is currently facing problems with high groundwater levels. By simulating the groundwater interaction with sewer systems and watercourses, we show that the groundwater table can increase up to 1 m under the impact of sewer rehabilitation and climate change. This increase will lead to significant flood risk in the residential area. We propose multiple technical solution scenarios and evaluate their effectiveness, demonstrating how the impact of increasing groundwater levels can be mitigated through implementation of drains during sewer reconstruction, but not completely avoided.