Sophistication of technology for assessment of the influence of topographical changes due to river denudations on underground and surface environments

Kawamura, Makoto; Nishiyama, Nariaki  ; Komatsu, Tetsuya  ; Jia, H.*; Koizumi, Yukiko*; Kabasawa, Satsuki ; Umeda, Koji*

In performance assessment of geological disposal of high-level radioactive waste, the impact of long-term changes in the surface environment, including topography caused by uplift and erosion, is important because the assessment period exceeds hundreds of thousands of years. One of the effects of uplift and denudation on the assessment of nuclide migration is the change in the location of groundwater discharge and recharge areas due to changes in topographical relief, such as river denudation, which is expected to affect the biosphere assessment process. As a tool to examine this issue, a "Analytical Tool of Evolution of Topography and Repository Depth" has been developed. On the other hand, it is necessary to verify how realistic the terrain created by this tool is for the performance assessment of the repository. In particular, there are few studies on transverse landforms formed by river cross section. In this report, we attempted a similar topographical analysis using actual and virtual topographical data for rivers, and report the results of a comparison and examination with river cross sections and runoff indexes, which are basic information necessary for performance assessment of disposal sites.