On the basis of non-steady gas diffusion theory, a portable apparatus was constructed to measure CO₂ diffusion coefficient of snow.It consists of a CO₂ supply chamber with an electrode CO₂ meter, a snow sample tube to be connected with the chamber and gas-supply equipment. After replacing the air in the chamber with CO₂ with known concentration, the temporal change of CO₂ concentration in the chamber was measured.Diffusion coefficients were calculated from the rate of concentration change and information of system geometry.
To examine the reliability of the apparatus, diffusion coefficient of CO₂ in glass beads and straight glass tube bundles of known geometry were measured.Obtained values showed close agreement with expected values. Reproducibility was excellent, giving relative variation of measurements less than 5%.CO₂ diffusion coefficients of newly fallen snow, granular snow and compacted snow, densities ranging between 0.10 and 0.55g/cm³, were measured.Measured values were between 0.40 and 0.89cm²/s (at0°C) and were proportional to the porosity of snow.The apparatus proved to be useful for field measurements.

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To establish an economic evaluation method of snow-removal systems, this paper dealt with the cost-effectiveness of snow-removing channels in calculating ratios of benefits by reduction in snow damage to snow-removal costs (B/C ratios). The snow-removal area for cost evaluation includes a road, a sidewalk, and a private area around the channel. The calculation was applied to the 1350.7-metre long snow-removing channel in Nagaoka-city. The calculated B/C ratios of the channel are 1.75 for a heavy snow with a 10-year mean recurrence interval, 1.11 for an average snow with a g-year recurrence, and 0.75 for a light snow with a 10-year recurrence. Consequently, it is concluded that the snow-removing channel is economically effective when the annual snowfall is heavier than average. From a comparison of cost-effectiveness of the channel and snow-melting water pipes, it showed that the channel gave higher B/C ratios when the channel was installed along a road in a densely populated district.

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In the design of machines for hydraulic transportation of snow, it is important to prevent blockages caused by an oversupply of snow into the stirring tank. A solid fraction detector of snow-water mixture in the stirring tank was developed on the basis of electric conductivity measurements of the mixture. Suitable configurations of electrodes were numerically analysed by a finite element method and were numerically analysed by a finite element method and confirmed with the experiments of a 20-liter model tank. The electrodes for an actual 1300-liter tank were designed by the finite element method and experimental errors of solid fraction values were less than 3%.

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A snowmelt model based on a heat balance method was applied to estimate basin-wide snowmelt from computed meterological data. A long-term snowmelt runoff of several basins was analysed by the tank model of Sugawara when limited meteorological data were available in using the heat balance method. To apply the tank model, basins were divided into 4 equal areas at different altitudes, and parameters of tanks and regional short-wave radiation, longwave radiation, and wind speed were computed by an optimization technique. Long-term snowmelt runoff was analysed with these parameters, and the result was compared with that of a snowmelt model using only the air temperature, so-called temperature index method. There was no significant difference in the accuracy of daily discharge estimations.

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Record-beaking heavy snowfalls were observed at Sapporo area in the Ishikari Plain, Hokkaido from December 1995 to January 1996. The total snowfall in December 1995 at Sapporo was 256cm which was more than twice of the monthly average.

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[in Japanese]

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[in Japanese]

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