Geophysical mapping and hydrogeological characterization of the subsurface to support the optimal placement of infiltration-based sustainable urban drainage systems

In 2050 about 70% of the world’s population of approximately 10 billion people will reside in urban areas. The continuous growth of cities in combination with future climate changes present authorities with significant challenges. As traditional urban sewer systems are designed for the present climate, the new precipitation pattern will increase the frequency of flooding in urban areas, which will hamper and destroy infrastructure, buildings, and the environment. One of the most significant challenges is to ensure a stable disposal of wastewater and surface water. An easy and economically feasible way to mitigate this is to introduce a Sustainable Urban Drainage System (SUDS) in the urban area. However, the lack of knowledge about the geological and hydrogeological setting hampers the use of SUDS. Based on 1315 ha of high-density electromagnetic (DUALEM-421S) data, detailed lithological soil descriptions of 614 boreholes, 153 infiltration tests and 250 in situ vane tests from 32 different sites in the Central Denmark Region this presentation will showcase how geophysical mapping in combination with lithological descriptions, infiltration tests and groundwater levels yield the basis for the construction of detailed planning maps showing the most suitable locations for infiltration. These maps provide unique information to the city planners by which a SUDS in a specific area may be restricted or precluded, as well as information about the expected performance of the SUDS.