Quantifying past and future erosion rates for potential radioactive waste repository sites in the South German Scarplands

Ensuring the long-term safety of underground repositories for high-level radioactive waste requires a comprehensive understanding of overburden stability. In this BGE-funded project, we investigate past landscape evolution and erosion dynamics in the South German Scarplands utilizing a multidisciplinary approach. Through geomorphic analysis, stratigraphic reconstruction, thermochronology, cosmogenic nuclides, and landscape evolution modelling, we aim to quantify the intricate interplay of geological processes shaping overburden topography over a million to a thousand year timescales.

Our findings reveal that long-wavelength uplift pulses and graben formation control long-term erosion within the region. Notably, the latest post-15 Ma uplift pulse has led to a southeastward shift of the drainage divide between the Main/Neckar and the Danube rivers, accompanied by substantial river captures and localized pulses of erosion. Associated peak erosion rates can be up to several tens of meters per thousand years and create a cascading effect of erosion away from the original capture sites along the antecedent river valleys. The magnitude of these events is constrained by the accumulated differential uplift between the base-level of the Rhine to the west and the uplifted area to the east (i.e., the Swabian Alb).

Furthermore, we highlight the profound influence of the exposure of 'weak' rocks and associated drainage system reorganization on both the past and future evolution of the South German Scarplands. Our comprehensive quantitative analysis contributes valuable insights into the complex interplay of geological processes governing landscape evolution and surface erosion, which are crucial for assessing the long-term safety of underground repositories for radioactive waste.