Shuji Yamada

Soil temperature, surface heave and downslope movements were monitored continuously for one year (1998-99) within a solifluction lobe developed on seasonally frozen ground in the Daisetsu Mountains, northern Japan. Observations were also made of soil moisture and ice segregation. Seasonal freeze-thaw cycles produced both frost creep and gelifluction. In layers shallower than 60cm, ice segregation during the freezing season induced seasonal frost heave, and ice melt at the same depths during the thaw season promoted gelifluction as well as seasonal frost creep. At greater depths, gelifluction did not occur even when the thaw plane reached the ice-rich layers. The results at the study site demonstrate that segregated ice plays an important role in gelifluction, but only at shallower depths. Copyright (C) 2010 John Wiley & Sons, Ltd.

A flexible print circuit(FPC) was printed on a spring steel strip to make a strain probe with a sufficient number of sections to measure the shearing displacement of soil, because current strain probes cannot detect shearing displacement. In addition, a two-gauge method was adopted with a pair of strain gauges attached to both sides of a section of the steel strip. We fashioned an FPC type strain probe 48 cm in length with 12 sections (i.e., each section length 4 cm). Shearing deformation tests (shearing thickness 2, 4 and 6 cm) were conducted on the FPC type probe and the current probe (section length 10 cm). The current type could not detect any shearing displacement, whereas the FPC type could detect that of a 4- and 6-cm shear-layer thickness with a 100% success ratio. In contrast, the FPC probe could detect only 33.3% of the shearing 2 cm in thickness. These results indicate that the FPC probe can detect shearing displacement when a section length is equivalent to or smaller than the shear layer thickness; in addition, it can detect shear displacement fairly accurately, but it overestimates the shearing layer thickness due to propagation of strain in the probe.

This study classified Japanese mountains based on mountain ordering using 1 : 500000 topographic maps, and examined the relationships of relief, relative relief and perimeter fractal dimension for the classified mountains. Mountain order was defined in terms of closed contour lines on the topographic map. A set of closed, concentric contour lines defines a first-order mountain. Higher-order mountains can be defined as a set of closed contour lines that contain lower-order mountains and that have only one closed contour line for each elevation. Relief, relative relief and fractal dimension were measured for ordered mountains using personal computer, and were defined as follows : relief E = H/A^1/2, where H and A are the height and area of each ordered mountain, respectively; relative relief R= ∑ h_i/H, where h_i is the height of the enclosed, lower-order mountains, and represents the degree of vertical roughness of the ordered mountain; fractal dimension was measured for perimeter contour line by the pixel dilation method, and represents the degree of horizontal roughness of the ordered mountain. Japanese mountains were classified into 74 third order mountains and 11 fourth order mountains. The area of a third order mountain varies from 50 to 4712 km², and that of a fourth order mountain is 2498 to 15563 km². A significant relationship was found among relief E, relative relief R, and fractal dimension D for the ordered mountains (r=0.91, n=85), and can be defined by the expression : <BR>LogE=-aD-bLogR-c<BR>This relationship shows that Japanese mountains have the following morphological characteristics : a high relief mountain has low vertical and horizontal roughness, and a low relief mountain has high vertical and horizontal roughness. These characteristics suggest that slope angle of Japanese mountains converges within a certain range.

The topographic parameters of mountains modified as residential land and golf courses are measured, and a new parameter, topographic naturalness, which describes the differences between natural and anthropogenic landforms are defined. Three topographic parameters, relief (E), relative relief (R) (degree of vertical roughness), and contour fractal dimension (D) (degree of horizontal roughness), of mountains in and around Tokyo, Nagoya, and Osaka are measured on topographic maps (1: 25, 000) published before and after modification of the sites. The three topographic parameters before modification showed a significant correlation (r=0.79, n=69, p<0.0001), and the regression plane was expressed as LogE=-0.31D-0.58 LogR-0.56. From this equation and actual D and R values, calculated LogE (LogE_cal) was obtained, and topographic naturalness, T, was defined as the difference between actual LogE (LogE_act), and LogE_cal: T=LogE_act-LogE_cal. The topographic naturalness of the mountains before modification was nearly 0: the mean was 0 and standard deviation was 0.15. After modification, the hills had low T values: the mean of residential land and golf courses was -0.20 and -0.05, respectively. These results show that topographic naturalness is a useful parameter for evaluating anthropogenic landforms.

Creep and temperature were monitored continuously from August 1996 to September 1997 in a solifluction lobe occurring over alpine, seasonally frozen substrate in the Daisetsu Mountains, northern Japan. The seasonal freeze-thaw cycle (&gt;100 cm in depth) caused relatively deep (95 cm in depth) frost creep (approximately 4 cm per year at the surface), whereas diurnal freeze-thaw cycles did not yield any measurable soil displacement. Diurnal freeze-thaw cycles took place frequently in autumn and spring (29 events per year), although the freezing was very shallow (&lt;10 cm). Because the soil at the measurement site has a surficial openwork bed that is non-frost-susceptible, the shallowness of the diurnal freeze-thaw cycles precluded surface frost creep. Since the soil is at least 100 cm thick, soil water stored induces frost heave and resultant creep at depth. Copyright (C) 2000 John Wiley & Sons, Ltd.

A new method for classifying mountain morphology, 'mountain ordering,' is proposed, and quantitative expressions for various morphological parameters of two ordered mountains in northern Japan were obtained using this method. Mountain order was defined in terms of the closed contour lines on a topographic map. A set of closed, concentric contour lines defines a first-order mountain. Higher-order mountains can be defined as a set of closed contour lines that contain lower-order mountains and that have only one closed contour line for each elevation; they are identified as m + 1th-order mountains, where m represents the order of the enclosed, lower-order mountains. The geomorphometry for a mountain ordered according to this definition permits the identification of systematic relationships between various morphological parameters. The relationships between mountain order and these morphological parameters follow a form similar to that of Horton's laws, and permit the calculation of the ratios of number, area and height; these parameters are sufficient to express the magnitude of a mountain's dissection. The sits-frequency distribution for area and height shows self-similarity for ordered mountains, and determines their fractal dimensions. Furthermore, the relationship between area and height, which has the form of a power function, describes the relief structure of ordered mountains. Copyright (C) 1999 John Wiley & Sons, Ltd.

Field measurements of soil creep and slope stability were conducted on a nose, side-slope and hollow in a zero order basin near Sapporo, Hokkaido, northern Japan, and the preferential location of soil creep and slope failure was determined. Soil creep was continuously measured by the strain probe method at three sites from 1994 to 1995, and was compared with soil moisture conditions and ground temperature. In the summer, active soil creep occurred only when rainfall led to large soil moisture changes and a near-saturated condition, which was most likely induced by shrink-swell activity of soil. In the winter, soil creep was caused by seasonal frost, although the mass transport was limited because of the insulation provided by snow covet. These results indicate that the soil moisture change and soil moisture content during a rainfall event in the summer are the major factors controlling soil creep in this basin. Soil moisture conditions were further measured by a tensiometer at 16 sites in the rainy season in 1994. On the nose and side-slope, active soil-moisture changes took place during rainfall-events. The hollow tended to maintain higher soil-moisture conditions than the nose and side-slope, because subsurface flow was concentrated in the hollow. Thus the soil-moisture variation that encourages soil creep rarely occurred in the hollow. From these results, sediment transport rates caused by creep were estimated to be 207.0, 159.5 and 9.0 x 10(-3) m(3)/yr on the nose, side-slope and hollow, respectively, and the resultant mass balances were calculated at - 207.0, +25.1 and + 172.9 x 10(-3) m(3)/yr, respectively. These results clearly show infilling in the hollow and denudation on the nose. Slope stability was analyzed by the infinite slope model. The potential of slope failure was evaluated from the relationship between critical water depth H-cr and soil thickness D. The analysis revealed that an increase in D causes a marked decrease in H-cr on the side-slope, indicating the high potential of slope failure on the slope. In contrast, both on the nose and in the hollow, the decrease in H-cr for the same increase in D was lower than that on the side-slope. However, slope failure on the side-slope and soil creep on the nose infill material into the hollow. Thus, the increase in D in the hollow is higher than that on the other slopes; leading to an increase in slope failure potential. These results indicate that soil creep and slope failure act as infilling and evacuating processes of the zero order basin with differing intensities depending on slope form: soil creep removes soil materials from the nose and deposits them in the hollow, whereas slope failure removes materials from the side-slope and deposits them in the hollow. When infilling develops a sufficiently thick soil accumulation in the hollow, slope failure evacuates the hollow. (C) 1999 Elsevier Science B.V. All rights reserved.

The maximum glacial extent and depression of equilibrium line altitudes (ELAs) in the Hiunchuli massif of West Nepal were reconstructed by air photograph interpretation. The present glaciers are characterized by either of the following two types: steep valley or valley sided type. On the other hand former glaciers were large plateau glaciers with many radial outlets. During the maximum glacial extent, the lowest ELA lay at an altitude of 4, 100m, about 1, 000m below the present ELA and the area of the maximum glacial extent was 200 km2, some 200 times as large as the present one.