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Yamaguchi, Masaaki; Kato, Tomoko; Suzuki, Yuji*; Makino, Hitoshi
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 27(2), p.72 - 82, 2020/12
An efficient analytical tool to calculate temporal change of topography and repository depth due to uplift and erosion was developed for use in performance assessment of high level radioactive waste geological disposal. The tool was developed as ArcGIS model, incorporating simplified landform development simulation, to enable trial calculation of various conditions such as initial topography, uplift rate and its distributions, and repository location. This tool enables to support decision on which processes, features, and their changes should be taken into account for performance assessment, by calculating topography change and repository depth change under various conditions.
Takai, Shizuka; Kimura, Hideo*; Uchikoshi, Emiko*; Munakata, Masahiro; Takeda, Seiji
JAEA-Data/Code 2020-007, 174 Pages, 2020/09
JAEA-Data-Code-2020-007.pdf:4.23MB
The MIG2DF computer code is a computer program that simulates groundwater flow and radionuclide transport in porous media for the safety assessment of radioactive waste disposal. The original version of MIG2DF was released in 1992. The original code employs a two-dimensional (vertical or horizontal cross-section, or an axisymmetric configuration) finite-element method to approximate the governing equations for density-dependent saturated-unsaturated groundwater flow and radionuclide transport. Meanwhile, for geological disposal of radioactive wastes, landscape evolution such as uplift and erosion needs to be assessed as a long-term geological and climate events, considering site conditions. In coastal areas, the impact to groundwater flow by change of salinity distribution to sea level change also needs to be considered. To deal with these events in the assessment, we have revised the original version of MIG2DF and developed the external program which enables MIG2DF to consider unsteady landscape evolution. In these developments, this report describes an upgrade of MIG2DF (Version 2) and presents the configuration, equations, methods, and verification. This reports also give the explanation external programs of MIG2DF: PASS-TRAC (the particle tracking code), PASS-PRE (the code for dataset preparation), and PASS-POST (the post-processing visualization system).
Onoe, Hironori; Kosaka, Hiroshi*; Matsuoka, Toshiyuki; Komatsu, Tetsuya; Takeuchi, Ryuji; Iwatsuki, Teruki; Yasue, Kenichi
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 26(1), p.3 - 14, 2019/06
In this study, it is focused on topographic changes due to uplift and denudation, also climate perturbations, a method which is able to assess the long-term variability of groundwater flow conditions using the coefficient variation based on some steady-state groundwater flow simulation results was developed. Spatial distribution of long residence time area which is not much influenced due to long-term topographic change and recharge rate change during the past one million years was able to estimate through the case study of the Tono area, Central Japan. By applying this evaluation method, it is possible to identify the local area that has low variability of groundwater flow conditions due to topographic changes and climate perturbations from the regional area quantitatively and spatially.
Shimada, Taro; Uchikoshi, Emiko*; Takai, Shizuka; Takeda, Seiji
no journal, ,
Long-term topographic change due to uplift, denudation and eustasy may change the field of groundwater flow and nuclide migration when radioactive wastes are disposed at the repository near the sea. In this report, we constructed the frame work for evaluating uncertainties of future topograophic changes. Using the evaluation code under developing at JAEA, we tried evaluating the future topographic change until 0.125k years after for catchment basin near the sea.
Takai, Shizuka; Shimada, Taro; Uchikoshi, Emiko*; Takeda, Seiji
no journal, ,
In geological disposal, landscape evolution by uplift, denudation, and sea-level change will change geological environment and decrease the depth of disposal. This may lower safety functions of disposal system: therefore, the effect needs to be evaluated properly. In the assessment, landscape evolution needs to be evaluated considering topography, material properties, and environmental factors. In addition, uncertainty should be considered for future sea-level change, which will significantly different from previous glacial cycles due to anthropogenic greenhouse-gas emissions. In this study, we evaluated future landscape evolution for a glacial-interglacial cycle (125 ka) by numerical simulation. Then, we conducted groundwater simulation considering transient topography and sea-level change. The uncertainty of future global sea-level change was considered based on previous studies by glacial isostatic adjustment simulation. The impact on groundwater flow was evaluated at the typical basin consisting of mountain, river, plain, and sea in Japan.
Kawamura, Makoto; Jia, H.*; Koizumi, Yukiko*; Nishiyama, Nariaki; Umeda, Koji*
no journal, ,
Using topographical analysis with GIS using 10 m DEM, we created 2 km river crossing lines on each side of the three rivers, Abegawa, Oigawa and Kumanogawa, starting from the estuary and going straight to the course of the river every 3 km. In addition, the geological information of the river transverse line was extracted. When the cross-sectional lines of the three rivers are displayed together, it can be seen that the river bed rises and the undulations increase as it goes upstream. A comparison of the cross-sectional shapes of the three rivers reveals similar trends, with peaks of undulations on both sides of the rivers in the middle to upper reaches located approximately 500-1,500 m from the center of the river. The relative height between bed and peak also tends to be around 200-600 m. The difference in elevation between the peaks on both sides of the river and the river bed increased in the upstream direction, that is, the depth of the valley to the river bed increased in the upstream direction. When the riverbed slope of the river longitudinal created from the riverbed elevation was taken, an inflection points where the slope trend rose from the upstream area was seen in all three rivers regardless of the geology and geological structure. Although the trend of elevation of the riverbed and increase in undulations from the relatively flat landform near the mouth of the river upstream is pseudo, it suggests a temporal process of landform formation due to uplift and denudation from the flat lowland. This will be information that contributes to verification of the validity of future predictions and performance evaluation models that incorporate topographical changes, such as topographical change simulations.
Shimada, Taro; Sasaki, Toshihisa*; Takai, Shizuka; Takeda, Seiji
no journal, ,
In Japan, shallow land disposal sites have already been and may be constructed in the future on marine terraces. It has been reported that deep-seated landslides, which are rapid erosions on terrace cliffs and hillslopes of streams formed on terrace faces, are dominant in the erosion of marine terraces. Therefore, the ability to handle deep-seated landslides is necessary to evaluate the effects of erosion on disposal sites during long-term topographic change. The Landlab code can evaluate deep-seated landslides as well as gradual erosion, mainly on hillslopes in mountainous areas. However, its applicability to marine terraces needs to be confirmed. In order to confirm the applicability of the evaluation model for deep-seated landslide of the Landlab to marine terraces, we first evaluated the occurrence points of deep-seated landslides using the Landlab with 2m DEM for an area with marine terraces. We then compared the points extracted by the Landlab with the hillslopes extracted by the manuals to determine the applicability of the Landlab's evaluation model. The target area was selected as an area with evidence of deep-seated landslides on marine terraces and streams. The points where deep-seated landslides are likely to occur in the future were evaluated for the field profile using the 2m DEM. The two manuals target the field profile and extract hillslopes where deep-seated landslides are likely to occur in the future based on the characteristics of the slope distribution considering the past landslide and topographic quantities in the same area using 2mDEM. Comparison of the extracted results of deep-seated landslides shows that most of the extracted points of deep-seated landslides by the Landlab were included in the possible deep-seated hillslopes extracted by the two manual methods. The results confirm that the Landlab's evaluation model is capable of extracting points where deep-seated landslides are likely to occur in the future.
Takai, Shizuka; Sanga, Tomoji*; Shimada, Taro; Takeda, Seiji
no journal, ,
In the safety assessment of intermediate-level radioactive waste disposal (the safety assessment period of 
10
years), numerical landscape evolution models (LEMs) are invaluable to assess the future considering future climate change. However, a limited number of studies have reported on the development of LEMs in the coastal area (Salles et al., 2016; Inoue and Tanaka, 2013). Moreover, the applicability of LEMs has not been verified for both erosion and deposition over a span of 10 years. In this study, we verified the capability of the JAEAsmtp (the LEMs developed by the Japan Atomic Energy Agency) in assessing coastal landscape evolution. First, we introduced the marine deposition model to the JAEAsmtp. From the feature of Holocene sedimentary structure at six coastal areas in Japan, the deposition is modelled by the planar distribution centering at the river mouth (gaussian: silt sedimentation around offshore, jet: sand sedimentation around the river mouth). In the virtual simulation of longitudinal river profile in the postglacial period, the typical delta response to sea-level change was formed. Second, the landscape evolution over the last glacial-interglacial cycle was simulated on the Kamikita coastal plain, where marine terraces (MIS5e, 7, 9) are widely distributed. The model parameters were calibrated through reconstruction of past landscape evolution (e.g., the erosion rate of marine terraces, the depth of buried valley). The validity of the LEMs was verified through the reconstruction of recent shoreline, the position of MIS5e marine terraces, and the formation of varied valley.
Yamaguchi, Masaaki; Kato, Tomoko; Suzuki, Yuji*; Kabasawa, Satsuki; Mihara, Morihiro; Makino, Hitoshi
no journal, ,
The topography and repository depth transition analysis tool developed for inland areas has been expanded to accommodate coastal areas (TARTAN-II), taking into consideration sediment transport from land to ocean, and their spatiotemporal change due to sea-level and climate changes.
Kawamura, Makoto; Nishiyama, Nariaki; Komatsu, Tetsuya; Jia, H.*; Kageyama, Soichiro*; Koizumi, Yukiko*; Nakanishi, Toshimichi*
no journal, ,
In geological disposal projects and safety regulations for high-level radioactive waste, one of the challenges in surveying and evaluating technology related to uplift and erosion, which is important in site selection and safety assessment of geological disposal, is that in the distant future, topography mainly due to river undercuts will occur. It is necessary to be able to quantitatively evaluate the changes and effects that these changes have on the underground geological environment. Among the geological environmental conditions, changes in groundwater recharge areas and outflow areas are important when building performance evaluation models because they can change the flow direction of surface water infiltration into the ground or groundwater outflow to the surface. This time, we selected rivers with different basin areas and uplift rates, and divided the basins into which we would like to measure the topographic features of each river. We measured 10 items of topographic features for the divided watersheds, and created data on trends in changes in topographic features. In addition, we calculated the "runoff index," which is defined as an index that expresses the ease or difficulty of surface runoff flow, and estimated and visualized the influence of river undercuts on topography. Regarding the rivers studied, the divided basins with high principal component scores of "basin average erosion height," "topographical complexity," and "basin relief number," which are indicators of topographical steepness among topographical features, were medium to high. There was a tendency to concentrate in the upper reaches. It was shown that the runoff index tends to be high in areas where high-elevation catchments are concentrated. Although this tendency is consistent with general understanding, I think it is significant that we were able to present this area classification quantitatively rather than qualitatively.
Nishiyama, Nariaki; Kawamura, Makoto; Komatsu, Tetsuya; Jia, H.*; Koizumi, Yukiko*; Nakanishi, Toshimichi*; Umeda, Koji*
no journal, ,
One of the key issues in the investigation and assessment technologies related to uplift and denudation, which are important for site selection and safety assessment of geological disposal of HLW, is the need to enable quantitative assessment of changes and their effects on the surface topography and geological environment in the distant future due to river cutting. In the study of performance assessment models that take into account landform development, simulations are based on information on river cross-section geometry, however information on river cross-section geometry has not been well organized. Against this background, the authors have obtained river cross-section data mainly for major rivers in Japan by GIS topographic analysis using the GSI's 10 m DEM (Kawamura et al., 2023). In this study, we expanded the data by increasing the number of target rivers and organized the data. In this presentation, we report the results of the comparison of cross-section profiles for each river, and the results of the grouping of specific height change from downstream to upstream and horizontal distance from riverbed to peak elevation by uplift rate, geology, climatic conditions, and other factors. These results will contribute to the validation of future projections such as landform development simulations and performance assessment models.
Takeuchi, Ryuji; Onoe, Hironori; Yasue, Kenichi
no journal, ,
In geological disposal for high-level radioactive waste, time scale for assessment is equal to or more than several hundreds of thousand years. During this time, the surface hydrological environment might change. Especially, changes of precipitation, evapotranspiration and runoff volume might cause a change of groundwater recharge rate (GRR), which is upper boundary condition of groundwater flow for deep underground. This study shows the method to estimate GRR considering the influence of changes for climate condition and landform condition as an example in Tono area. The GRRs of 0.45 Ma are estimated 118% to 237% of the current GRR, and the GRRs of 0.14 Ma are estimated 81% to 196% of the current GRR. In the result of current topography in the glacial period, the recharge rate is estimated 58% to 72% of the current GRR. However it's not possible to estimate the runoff volume based on the topography of 1.0 Ma, which is estimated poor undulations and flat terrains.
Takai, Shizuka; Sanga, Tomoji*; Shimada, Taro; Takeda, Seiji
no journal, ,
In the safety assessment of intermediate-level radioactive waste disposal (the safety assessment period of 10 years), numerical landscape evolution models (LEMs) are invaluable to assess the future considering climate change. However, the most parameters of LEMs cannot be determined directly from the measurement. In this study, we constructed a framework of calibration and validation of LEMs parameters based on the simulation over the last 125 ka. Using the LEMs developed by JAEA, the constructed framework was verified in the Kamikita coastal plain. (i) calibration (the Tokusari River watershed): we found the set of LEMs parameters that satisfy the constraint conditions of the past landscape evolution (terrace erosion rates, depth of the buried valley, longitudinal river profile, width of erosional valley-floor). For efficient calibration, we firstly selected parameters for calibration based on the Morris sensitivity analysis. Then, the best parameter set was estimated by approximating the constraint conditions by second-order polynomial surrogate models of selected parameters. Through the calibration, five parameters are identified as important: the coefficients of hillslope transport, fluvial incision, coastal erosion, and climate change. The developed surrogate models are approximated the simulation results with the 0.7 or more coefficient determination. (ii) validation (the Futamata River watershed): we finally validate the result by applying the calibrated parameters to an independent watershed. As the result of simulation from 125 ka to present, the residual of reproduced and recent topography is less than 
15 m for 80% in the area both of the calibration and validation domain. The validity of calibration was further verified through reproducibility of buried valley, terrace cliff, and terrace erosion rates.
Takai, Shizuka; Shimada, Taro; Uchikoshi, Emiko*; Takeda, Seiji
no journal, ,
In geological disposal, landscape evolution by uplift, denudation, and sea-level change will change geological environment and decrease the depth of disposal. This may lower safety functions of disposal system: therefore, the effect needs to be evaluated properly. Landscape evolution can be evaluated quantitatively using landscape evolution models. In general, the evaluation is based on extrapolation of the past. However, the future sea-level change may differ from the past because of greenhouse gases. In this study, we constructed the evaluation method for future long-term landscape evolution based on the past landscape evolution. We confirm the applicability in the typical basin consisting of mountain, river, plain, and sea. The effect to future landscape evolution by uncertainties of sea-level change were evaluated.
Takeda, Seiji
no journal, ,
no abstracts in English
Takai, Shizuka; Sanga, Tomoji*; Shimada, Taro; Takeda, Seiji
no journal, ,
Prediction of long-term future landscape evolution is indispensable for safety assessment for intermediate radioactive waste disposal, whose safety assessment period is ~10 years. To assess the coastal landscape evolution considering the uncertainty of future sea-level change, the numerical simulation based on the landscape evolution models (LEMs) will be valuable. However, the applicability of LEMs over 10 years has not been verified in coastal areas. JAEA has developed a LEMs (JAEAsmtp) coupling hillslope and fluvial transport, tectonics, marine sedimentation, sea-level and climate change, and lithology. In this study, we demonstrate the capabilities of JAEAsmtp in assessing the coastal landscape evolution over the last glacial-interglacial cycle. Our target area (250 km
) is located on the Kamikita coastal plain (sedimentary rock), where the marine terraces (MIS5e, 7, 9) are widely distributed. First, based on the marine terraces, borehole, and sonic prospecting data, the spatial distributions of the present and paleo-elevation, uplift rate, and alluvial deposits were estimated. Second, the LEMs parameters for fluvial incision and erodibilities were obtained from the slope-area analysis and soil-test data, respectively. Finally, the landscape evolution from MIS5e (125 ka) to present was simulated. By incorporating the drift sand into JAEAsmtp, the applicability was confirmed via reproducibility of the present coastal line and the distribution of alluvial deposits.
Kawamura, Makoto; Nishiyama, Nariaki; Komatsu, Tetsuya; Jia, H.*; Koizumi, Yukiko*; Kabasawa, Satsuki; Umeda, Koji*
no journal, ,
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.
Nishiyama, Nariaki; Kawamura, Makoto; Komatsu, Tetsuya; Jia, H.*; Koizumi, Yukiko*; Kabasawa, Satsuki; Nakanishi, Toshimichi*; Umeda, Koji*
no journal, ,
no abstracts in English
Kawamura, Makoto; Nishiyama, Nariaki; Komatsu, Tetsuya; Jia, H.*; Koizumi, Yukiko*; Kabasawa, Satsuki; Nakanishi, Toshimichi*; Umeda, Koji*
no journal, ,
In geological disposal projects and safety regulations for HLW, one of the challenges in surveying and evaluating technology related to uplift and erosion, which is important in site selection and safety assessment of geological disposal, is that in the distant future, topography mainly due to river undercuts will occur. It is necessary to be able to quantitatively evaluate the changes and effects that these changes have on the underground geological environment. Among the geological environmental conditions, changes in groundwater recharge areas and outflow areas are important when building performance evaluation models because they can change the flow direction of surface water infiltration into the ground or groundwater outflow to the surface. The most reliable way to evaluate recharge and discharge areas is to use actual measured data on precipitation and river flow. However, when dealing with past or future topography, or hypothetical topography generated by simulations of topographical change, actual measurements are not possible, and so technology is required to indirectly estimate the area from topographical information. As one of the research technologies, a method has been developed to measure topographical features using a digital elevation model, calculate runoff volume using statistical analysis techniques, and visualize it as an index. In previous studies, we also attempted to apply this method to three rivers which have different drainage basin areas and uplift rates, and were able to present, to a certain extent quantitatively, results that are consistent with the general understanding that areas where high-altitude divided drainage basins are concentrated are high, meaning that surface water tends to flow more easily. Here, following previous studies, we report an example of applying the same method to a virtual topography created by simulating topographical change, and comparing and examining it with an actual river.
