The past is the key to the future – considering Pleistocene subglacial erosion for the minimum depth of a radioactive waste repository

Abstract

Erosion during potential future glaciations, especially the incision of deep tunnel valleys, is a major challenge for the long-term safety of a radioactive waste repository. Tunnel valleys are a common feature of formerly glaciated sedimentary basins and were incised by pressurised subglacial meltwater. Besides glaciological conditions, tunnel-valley formation depends strongly on the erodibility and hydraulic conductivity of the substratum. In northern Germany, tunnel valleys formed during the Pleistocene glaciations are widespread and may attain depths of almost 600 m. The Pleistocene record may provide an indication for the potential regional distribution and maximum depth of future glaciogenic erosion. We present a new overview map of the maximum depth of Pleistocene erosion in northern Germany. Depth zones were extracted from the existing data and maps provided by the state geological surveys. Based on the mapped depth zones, the potential for future tunnel-valley formation can be assessed. The map may serve as a base to define a spatially variable additional depth that should be added to the minimum depth of a repository required by legislation.