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This paper describes a method to estimate depth of new snowfall automatically from measurements of hourly total snow depth and precipitation, based on viscous compression theory. Depth of new snow deposited for a time interval is given by adding settlement depth of old snow to the change of total snow depth during the interval, because snow cover is continuously settling due to its own weight.Then, assuming that a relation between compressive viscosity η and dry density ρ_dry of snow is expressed by η=C(ρ_dry)^a with constants of C and a, an equation computing time variation of thickness of a snow layer from data of precipitation was derived theoretically. Using the equation, the settlement depth was computed and the depth of daily new snowfall was estimated. The results using C=0.392 Pa·s (kg·m^-3)^-a and a=3.6, which are nearly equal to the values obtained for dry snow, were found to be in a good agreement with data of daily new snow depth measured in Tohkamachi during three winters from 1992-1993. The average and maximum errors were 1.71cm and about±5cm, respectively.

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An economically optimum criterion for snow-plowing operation on roads was presented with calculation of annual cost of snow damage. The cost of snow damage is defined as the sum of benefit reduction by snow accumulation and snow-removing cost. Annual benefit reduction on the road was calculated as a cumulative value of the daily traffic prevention factor (TPF), which is estimated as a function of daily amount of snow left on the road, multiplied by daily financial loss. Annual cost for snow-plowing operation was proportional to the number of snow-removing days.Both cumulative TPF and the number of snow-plowing activities were simulated when a snow-removing criterion and some meteorological data were given. The most economical calculated criterion for the urban snow removal of Nagaoka City was when the snow on the road was in a range between 5 and 9 kg/m² regardless of the snow abundance; this is almost the same as the current mobilization criterion for snow plows.

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Owing to severe rainfall on 11 and 12 July, 1995, a debris flow occurred and flowed down on the Shirouma-daisekkei snow patch, the Northern Japanese Alps. As a result, the snow patch was widely covered with debris flow deposits, the debris flow incised the snow patch, and a large-scale trench (1.3 km in length, 6-8 m in width, 10-20 m in depth) was formed. The trench was formed at the center of debris covered area, from the uppermost part to near the terminus of the snow patch. The width of the trench became more than 15 m on 18 October as a result of continuous snowmelt in summer and the area of the trench reached 20% of the entire snow patch area. Internal structures of the snow patch, such as firn aquifer and dirt layers which were composed of sand and gravel, were recognized on the side walls of this trench. However, no ice body was found on the side walls.
Formation processes of this trench are discussed on the bases of distribution and shape of the trench and debris covered area which were obtained from aerial photographs and field observations. It is concluded that the trench was formed since the debris flow eroded firn layers. On this snow patch, the similar kind trench was also formed in 1952. In order to understand formation and maintenance processes of perennial snow patches, it must be important to evaluate such influences of debris flow on snow patches.

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Flow conditions were reconstructed for 18 alpine glaciers in the Hidaka Range, during the LGM (Last Glacial Maximum, about 18, 000 y.B.P.), assuming a plastic and laminar flow without basal sliding.Reconstructed annual discharge through the cross section at the ELA (Equilibrium Line Altitude)on 18 glaciers almost coincided with the amount of reconstructed annual net ablation (or accumulation)below(or above)the ELA, when the mean ice temperature was assumed to be -7°C and -8°C, together with assumed air temperature cooling of 6°8°C.The flow velocity range at the center of the ELA was between 1 and 20 m/a, depending on the surface gradient and the ice thickness.Comparison of these flow velocities with those of present day glaciers, without basal sliding, suggests that the glaciers of the Hidaka Range during the LGM were similar in character to small modern cirque and valley glaciers in the world.

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