Detailed Geological Modeling in Urban Areas: Focus on Surface Near Geology and Anthropogenic Layer

In the last few years, there’s an increased focus on detailed geological modeling in urban areas. The models serve as important input to hydrological models. This focus is partly due to climate changes as high intensity rainfalls are seen more often than in the past, and water recharge is a topic too. In urban areas, this arises new challenges. There is a need of a high level of detailed geological knowledge for the uppermost zone of the soil, which typically are problematic due to practically limitations, especially when using geological layer models. Furthermore, to accommodate the need of a high detail, all relevant available data should be used in the modeling process. Human activity has deeply changed the soil layers, e.g. by constructions as roadbeds, buildings basements, pipelines, landfill etc. These elements can act as barriers or pathways regarding surface near groundwater flow and can attribute to local flooding or mobilization and transport of contaminants etc.

Geophysical methods are being developed with focus on mapping the uppermost geological layers in e.g. urban areas, and these data can be evaluated against e.g. borehole data and infiltration tests.

The different datatypes, including information from subsurface structural elements (road beds, pipelines, traces etc.) can be combined and interpreted together in geological voxel models.

A geological voxel model is built by small boxes (voxels). Each box can be assigned different parameters, ex. lithology, transmissivity or contaminant concentration. Human related elements can be implemented using tools, which gives the modeler advanced options for making detailed small-scale models.

This paper demonstrates opportunities, tools, workflow and a resulting geological model for a case area in Denmark.